From 32d95eccd78ac1c90b55568867e035f0fd5f3481 Mon Sep 17 00:00:00 2001
From: catch <catch@35733.no-reply.drupal.org>
Date: Fri, 8 Nov 2019 13:39:33 +0000
Subject: [PATCH] Issue #3082655 by Wim Leers, alexpott, iyyappan.govind, dww,
 lauriii: Specify the $defaultTheme property in all functional tests

---
 .../tests/src/Functional/ActionListTest.php   |   5 +++++
 .../src/Functional/ActionUninstallTest.php    |   5 +++++
 .../src/Functional/ConfigurationTest.php      |   6 ++++++
 .../ActionFormAjaxTest.php                    |   5 +++++
 .../tests/src/Functional/AddFeedTest.php      |   5 +++++
 .../src/Functional/AggregatorAdminTest.php    |   5 +++++
 .../src/Functional/AggregatorCronTest.php     |   5 +++++
 .../AggregatorDisplayConfigurableTest.php     |   5 +++++
 .../Functional/AggregatorRenderingTest.php    |   5 +++++
 .../src/Functional/DeleteFeedItemTest.php     |   5 +++++
 .../tests/src/Functional/DeleteFeedTest.php   |   5 +++++
 .../src/Functional/FeedAdminDisplayTest.php   |   5 +++++
 .../src/Functional/FeedCacheTagsTest.php      |   5 +++++
 .../src/Functional/FeedFetcherPluginTest.php  |   5 +++++
 .../tests/src/Functional/FeedLanguageTest.php |   5 +++++
 .../tests/src/Functional/FeedParserTest.php   |   5 +++++
 .../Functional/FeedProcessorPluginTest.php    |   5 +++++
 .../Functional/Hal/FeedHalJsonAnonTest.php    |   5 +++++
 .../Hal/FeedHalJsonBasicAuthTest.php          |   5 +++++
 .../Functional/Hal/FeedHalJsonCookieTest.php  |   5 +++++
 .../Functional/Hal/ItemHalJsonAnonTest.php    |   5 +++++
 .../Hal/ItemHalJsonBasicAuthTest.php          |   5 +++++
 .../Functional/Hal/ItemHalJsonCookieTest.php  |   5 +++++
 .../tests/src/Functional/ImportOpmlTest.php   |   5 +++++
 .../src/Functional/ItemCacheTagsTest.php      |   5 +++++
 .../src/Functional/Rest/FeedJsonAnonTest.php  |   5 +++++
 .../Functional/Rest/FeedJsonBasicAuthTest.php |   5 +++++
 .../Functional/Rest/FeedJsonCookieTest.php    |   5 +++++
 .../src/Functional/Rest/FeedXmlAnonTest.php   |   5 +++++
 .../Functional/Rest/FeedXmlBasicAuthTest.php  |   5 +++++
 .../src/Functional/Rest/FeedXmlCookieTest.php |   5 +++++
 .../src/Functional/Rest/ItemJsonAnonTest.php  |   5 +++++
 .../Functional/Rest/ItemJsonBasicAuthTest.php |   5 +++++
 .../Functional/Rest/ItemJsonCookieTest.php    |   5 +++++
 .../src/Functional/Rest/ItemXmlAnonTest.php   |   5 +++++
 .../Functional/Rest/ItemXmlBasicAuthTest.php  |   5 +++++
 .../src/Functional/Rest/ItemXmlCookieTest.php |   5 +++++
 .../src/Functional/UpdateFeedItemTest.php     |   5 +++++
 .../tests/src/Functional/UpdateFeedTest.php   |   5 +++++
 .../src/Functional/IpAddressBlockingTest.php  |   5 +++++
 .../tests/src/Functional/BasicAuthTest.php    |   5 +++++
 .../tests/src/Functional/BigPipeTest.php      |   5 +++++
 .../BigPipeRegressionTest.php                 |   5 +++++
 .../src/Functional/BlockAdminThemeTest.php    |   5 +++++
 .../tests/src/Functional/BlockCacheTest.php   |   5 +++++
 .../tests/src/Functional/BlockDemoTest.php    |   5 +++++
 .../src/Functional/BlockFormInBlockTest.php   |   5 +++++
 .../src/Functional/BlockHiddenRegionTest.php  |   5 +++++
 .../src/Functional/BlockHookOperationTest.php |   5 +++++
 .../tests/src/Functional/BlockHtmlTest.php    |   5 +++++
 .../tests/src/Functional/BlockInstallTest.php |   5 +++++
 .../src/Functional/BlockInvalidRegionTest.php |   5 +++++
 .../src/Functional/BlockLanguageCacheTest.php |   5 +++++
 .../src/Functional/BlockLanguageTest.php      |   5 +++++
 .../src/Functional/BlockRenderOrderTest.php   |   5 +++++
 .../Functional/BlockSystemBrandingTest.php    |   5 +++++
 .../block/tests/src/Functional/BlockTest.php  |   5 +++++
 .../tests/src/Functional/BlockUiTest.php      |   5 +++++
 .../tests/src/Functional/BlockXssTest.php     |   5 +++++
 .../Functional/Hal/BlockHalJsonAnonTest.php   |   5 +++++
 .../Hal/BlockHalJsonBasicAuthTest.php         |   5 +++++
 .../Functional/Hal/BlockHalJsonCookieTest.php |   5 +++++
 .../Functional/NonDefaultBlockAdminTest.php   |   5 +++++
 .../src/Functional/Rest/BlockJsonAnonTest.php |   5 +++++
 .../Rest/BlockJsonBasicAuthTest.php           |   5 +++++
 .../Functional/Rest/BlockJsonCookieTest.php   |   5 +++++
 .../src/Functional/Rest/BlockXmlAnonTest.php  |   5 +++++
 .../Functional/Rest/BlockXmlBasicAuthTest.php |   5 +++++
 .../Functional/Rest/BlockXmlCookieTest.php    |   5 +++++
 .../src/Functional/Views/DisplayBlockTest.php |   5 +++++
 .../FunctionalJavascript/BlockFilterTest.php  |   5 +++++
 .../Functional/BlockContentCacheTagsTest.php  |   5 +++++
 .../BlockContentContextualLinksTest.php       |   5 +++++
 .../Functional/BlockContentCreationTest.php   |   5 +++++
 .../src/Functional/BlockContentListTest.php   |   5 +++++
 .../Functional/BlockContentListViewsTest.php  |   5 +++++
 .../Functional/BlockContentPageViewTest.php   |   5 +++++
 .../Functional/BlockContentRevisionsTest.php  |   5 +++++
 .../src/Functional/BlockContentSaveTest.php   |   5 +++++
 .../BlockContentTranslationUITest.php         |   5 +++++
 .../src/Functional/BlockContentTypeTest.php   |   5 +++++
 .../Functional/BlockContentValidationTest.php |   5 +++++
 .../Hal/BlockContentHalJsonAnonTest.php       |   5 +++++
 .../Hal/BlockContentHalJsonBasicAuthTest.php  |   5 +++++
 .../Hal/BlockContentHalJsonCookieTest.php     |   5 +++++
 .../Hal/BlockContentTypeHalJsonAnonTest.php   |   5 +++++
 .../BlockContentTypeHalJsonBasicAuthTest.php  |   5 +++++
 .../Hal/BlockContentTypeHalJsonCookieTest.php |   5 +++++
 .../tests/src/Functional/PageEditTest.php     |   5 +++++
 .../Rest/BlockContentJsonAnonTest.php         |   5 +++++
 .../Rest/BlockContentJsonBasicAuthTest.php    |   5 +++++
 .../Rest/BlockContentJsonCookieTest.php       |   5 +++++
 .../Rest/BlockContentTypeJsonAnonTest.php     |   5 +++++
 .../BlockContentTypeJsonBasicAuthTest.php     |   5 +++++
 .../Rest/BlockContentTypeJsonCookieTest.php   |   5 +++++
 .../Rest/BlockContentTypeXmlAnonTest.php      |   5 +++++
 .../Rest/BlockContentTypeXmlBasicAuthTest.php |   5 +++++
 .../Rest/BlockContentTypeXmlCookieTest.php    |   5 +++++
 .../Rest/BlockContentXmlAnonTest.php          |   5 +++++
 .../Rest/BlockContentXmlBasicAuthTest.php     |   5 +++++
 .../Rest/BlockContentXmlCookieTest.php        |   5 +++++
 .../src/Functional/UnpublishedBlockTest.php   |   5 +++++
 .../Views/BlockContentFieldFilterTest.php     |   5 +++++
 .../Views/BlockContentIntegrationTest.php     |   5 +++++
 .../Views/BlockContentRedirectTest.php        |   5 +++++
 .../Views/BlockContentWizardTest.php          |   5 +++++
 .../src/Functional/Views/FieldTypeTest.php    |   5 +++++
 .../tests/src/Functional/BlockPlaceTest.php   |   5 +++++
 .../src/Functional/BookBreadcrumbTest.php     |   5 +++++
 .../Functional/BookContentModerationTest.php  |   5 +++++
 .../book/tests/src/Functional/BookTest.php    |   5 +++++
 .../Functional/Views/BookRelationshipTest.php |   5 +++++
 .../BookJavascriptTest.php                    |   5 +++++
 .../src/Functional/CKEditorAdminTest.php      |   5 +++++
 .../src/Functional/CKEditorLoadingTest.php    |   5 +++++
 .../CKEditorStylesComboAdminTest.php          |   5 +++++
 .../Functional/CKEditorToolbarButtonTest.php  |   5 +++++
 .../src/FunctionalJavascript/AjaxCssTest.php  |   5 +++++
 .../CKEditorIntegrationTest.php               |   5 +++++
 .../src/Functional/ColorConfigSchemaTest.php  |   5 +++++
 .../src/Functional/ColorSafePreviewTest.php   |   5 +++++
 .../color/tests/src/Functional/ColorTest.php  |   5 +++++
 .../src/Functional/CommentAccessTest.php      |   5 +++++
 .../src/Functional/CommentActionsTest.php     |   5 +++++
 .../tests/src/Functional/CommentAdminTest.php |   5 +++++
 .../src/Functional/CommentAnonymousTest.php   |   5 +++++
 .../tests/src/Functional/CommentBlockTest.php |   5 +++++
 .../tests/src/Functional/CommentBookTest.php  |   5 +++++
 .../tests/src/Functional/CommentCSSTest.php   |   5 +++++
 .../src/Functional/CommentCacheTagsTest.php   |   5 +++++
 .../src/Functional/CommentEntityTest.php      |   5 +++++
 .../src/Functional/CommentFieldsTest.php      |   5 +++++
 .../src/Functional/CommentInterfaceTest.php   |   5 +++++
 .../src/Functional/CommentLanguageTest.php    |   5 +++++
 .../src/Functional/CommentLinksAlterTest.php  |   5 +++++
 .../tests/src/Functional/CommentLinksTest.php |   5 +++++
 .../Functional/CommentNewIndicatorTest.php    |   5 +++++
 .../src/Functional/CommentNodeAccessTest.php  |   5 +++++
 .../src/Functional/CommentNodeChangesTest.php |   5 +++++
 .../src/Functional/CommentNonNodeTest.php     |   5 +++++
 .../tests/src/Functional/CommentPagerTest.php |   5 +++++
 .../tests/src/Functional/CommentRssTest.php   |   5 +++++
 .../src/Functional/CommentStatisticsTest.php  |   5 +++++
 .../CommentStatusFieldAccessTest.php          |   5 +++++
 .../src/Functional/CommentThreadingTest.php   |   5 +++++
 .../tests/src/Functional/CommentTitleTest.php |   5 +++++
 .../Functional/CommentTokenReplaceTest.php    |   5 +++++
 .../Functional/CommentTranslationUITest.php   |   5 +++++
 .../tests/src/Functional/CommentTypeTest.php  |   5 +++++
 .../Functional/Hal/CommentHalJsonAnonTest.php |   5 +++++
 .../Hal/CommentHalJsonBasicAuthTest.php       |   5 +++++
 .../Hal/CommentHalJsonCookieTest.php          |   5 +++++
 .../Hal/CommentTypeHalJsonAnonTest.php        |   5 +++++
 .../Hal/CommentTypeHalJsonBasicAuthTest.php   |   5 +++++
 .../Hal/CommentTypeHalJsonCookieTest.php      |   5 +++++
 .../Functional/Rest/CommentJsonAnonTest.php   |   5 +++++
 .../Rest/CommentJsonBasicAuthTest.php         |   5 +++++
 .../Functional/Rest/CommentJsonCookieTest.php |   5 +++++
 .../Rest/CommentTypeJsonAnonTest.php          |   5 +++++
 .../Rest/CommentTypeJsonBasicAuthTest.php     |   5 +++++
 .../Rest/CommentTypeJsonCookieTest.php        |   5 +++++
 .../Rest/CommentTypeXmlAnonTest.php           |   5 +++++
 .../Rest/CommentTypeXmlBasicAuthTest.php      |   5 +++++
 .../Rest/CommentTypeXmlCookieTest.php         |   5 +++++
 .../Functional/Rest/CommentXmlAnonTest.php    |   5 +++++
 .../Rest/CommentXmlBasicAuthTest.php          |   5 +++++
 .../Functional/Rest/CommentXmlCookieTest.php  |   5 +++++
 .../src/Functional/Views/CommentAdminTest.php |   5 +++++
 .../Views/CommentFieldFilterTest.php          |   5 +++++
 .../Views/CommentOperationsTest.php           |   5 +++++
 .../Views/CommentRestExportTest.php           |   5 +++++
 .../src/Functional/Views/CommentRowTest.php   |   5 +++++
 .../Views/DefaultViewRecentCommentsTest.php   |   5 +++++
 .../src/Functional/Views/NodeCommentsTest.php |   5 +++++
 .../tests/src/Functional/Views/RowRssTest.php |   5 +++++
 .../tests/src/Functional/Views/WizardTest.php |   5 +++++
 .../Hal/ConfigTestHalJsonAnonTest.php         |   5 +++++
 .../Hal/ConfigTestHalJsonBasicAuthTest.php    |   5 +++++
 .../Hal/ConfigTestHalJsonCookieTest.php       |   5 +++++
 .../Rest/ConfigTestJsonAnonTest.php           |   5 +++++
 .../Rest/ConfigTestJsonBasicAuthTest.php      |   5 +++++
 .../Rest/ConfigTestJsonCookieTest.php         |   5 +++++
 .../Functional/Rest/ConfigTestXmlAnonTest.php |   5 +++++
 .../Rest/ConfigTestXmlBasicAuthTest.php       |   5 +++++
 .../Rest/ConfigTestXmlCookieTest.php          |   5 +++++
 ...yMetadataConfigOverrideIntegrationTest.php |   5 +++++
 .../Functional/ConfigDependencyWebTest.php    |   5 +++++
 .../ConfigDraggableListBuilderTest.php        |   5 +++++
 .../ConfigEntityFormOverrideTest.php          |   5 +++++
 .../ConfigEntityListMultilingualTest.php      |   5 +++++
 .../src/Functional/ConfigEntityListTest.php   |   5 +++++
 .../Functional/ConfigEntityStatusUITest.php   |   5 +++++
 .../tests/src/Functional/ConfigEntityTest.php |   5 +++++
 .../Functional/ConfigExportImportUITest.php   |   5 +++++
 .../src/Functional/ConfigExportUITest.php     |   5 +++++
 .../src/Functional/ConfigFormOverrideTest.php |   5 +++++
 .../ConfigImportInstallProfileTest.php        |   5 +++++
 .../src/Functional/ConfigImportUITest.php     |   5 +++++
 .../src/Functional/ConfigImportUploadTest.php |   5 +++++
 .../ConfigInstallProfileOverrideTest.php      |   5 +++++
 ...figInstallProfileUnmetDependenciesTest.php |   5 +++++
 .../src/Functional/ConfigInstallWebTest.php   |   5 +++++
 .../ConfigLanguageOverrideWebTest.php         |   5 +++++
 .../src/Functional/ConfigOtherModuleTest.php  |   5 +++++
 .../ConfigSingleImportExportTest.php          |   5 +++++
 .../LanguageNegotiationFormOverrideTest.php   |   5 +++++
 .../SchemaConfigListenerWebTest.php           |   5 +++++
 .../TransformedConfigExportImportUITest.php   |   5 +++++
 .../FunctionalJavascript/ConfigEntityTest.php |   5 +++++
 .../Functional/ConfigTranslationCacheTest.php |   5 +++++
 .../ConfigTranslationDateFormatUiTest.php     |   5 +++++
 .../ConfigTranslationListUiTest.php           |   5 +++++
 .../ConfigTranslationOverviewTest.php         |   5 +++++
 .../Functional/ConfigTranslationUiTest.php    |   5 +++++
 .../ConfigTranslationUiThemeTest.php          |   5 +++++
 .../ConfigTranslationViewListUiTest.php       |   5 +++++
 .../ConfigTranslationUiTest.php               |   5 +++++
 .../src/Functional/ContactLanguageTest.php    |   5 +++++
 .../src/Functional/ContactPersonalTest.php    |   5 +++++
 .../src/Functional/ContactSitewideTest.php    |   5 +++++
 .../src/Functional/ContactStorageTest.php     |   5 +++++
 .../Hal/ContactFormHalJsonAnonTest.php        |   5 +++++
 .../Hal/ContactFormHalJsonBasicAuthTest.php   |   5 +++++
 .../Hal/ContactFormHalJsonCookieTest.php      |   5 +++++
 .../Functional/Hal/MessageHalJsonAnonTest.php |   5 +++++
 .../Hal/MessageHalJsonBasicAuthTest.php       |   5 +++++
 .../Hal/MessageHalJsonCookieTest.php          |   5 +++++
 .../Rest/ContactFormJsonAnonTest.php          |   5 +++++
 .../Rest/ContactFormJsonBasicAuthTest.php     |   5 +++++
 .../Rest/ContactFormJsonCookieTest.php        |   5 +++++
 .../Rest/ContactFormXmlAnonTest.php           |   5 +++++
 .../Rest/ContactFormXmlBasicAuthTest.php      |   5 +++++
 .../Rest/ContactFormXmlCookieTest.php         |   5 +++++
 .../Functional/Rest/MessageJsonAnonTest.php   |   5 +++++
 .../Rest/MessageJsonBasicAuthTest.php         |   5 +++++
 .../Functional/Rest/MessageJsonCookieTest.php |   5 +++++
 .../Functional/Rest/MessageXmlAnonTest.php    |   5 +++++
 .../Rest/MessageXmlBasicAuthTest.php          |   5 +++++
 .../Functional/Rest/MessageXmlCookieTest.php  |   5 +++++
 .../src/Functional/Views/ContactLinkTest.php  |   5 +++++
 ...onAdminPathEntityConverterLanguageTest.php |   5 +++++
 .../ContentModerationWorkflowTypeTest.php     |   5 +++++
 .../Functional/DefaultModerationStateTest.php |   5 +++++
 ...uilderContentModerationIntegrationTest.php |   5 +++++
 .../Functional/ModeratedContentViewTest.php   |   5 +++++
 .../src/Functional/ModerationActionsTest.php  |   5 +++++
 .../ModerationContentTranslationTest.php      |   5 +++++
 .../src/Functional/ModerationFormTest.php     |   5 +++++
 .../src/Functional/ModerationLocaleTest.php   |   5 +++++
 .../ModerationRevisionRevertTest.php          |   5 +++++
 .../Functional/ModerationStateAccessTest.php  |   5 +++++
 .../Functional/ModerationStateBlockTest.php   |   5 +++++
 .../Functional/ModerationStateNodeTest.php    |   5 +++++
 .../ModerationStateNodeTypeTest.php           |   5 +++++
 .../tests/src/Functional/NodeAccessTest.php   |   5 +++++
 .../ViewsModerationStateFilterTest.php        |   5 +++++
 ...kspaceContentModerationIntegrationTest.php |   5 +++++
 .../ContentTestTranslationUITest.php          |   5 +++++
 .../ContentTranslationContextualLinksTest.php |   5 +++++
 .../ContentTranslationDisableSettingTest.php  |   5 +++++
 .../ContentTranslationEnableTest.php          |   5 +++++
 .../ContentTranslationEntityBundleUITest.php  |   5 +++++
 .../ContentTranslationLanguageChangeTest.php  |   5 +++++
 .../ContentTranslationLinkTagTest.php         |   5 +++++
 .../ContentTranslationOperationsTest.php      |   5 +++++
 ...slationOutdatedRevisionTranslationTest.php |   5 +++++
 ...slationRevisionTranslationDeletionTest.php |   5 +++++
 .../ContentTranslationSettingsTest.php        |   5 +++++
 .../ContentTranslationSyncImageTest.php       |   5 +++++
 .../ContentTranslationUISkipTest.php          |   5 +++++
 ...entTranslationUntranslatableFieldsTest.php |   5 +++++
 .../ContentTranslationWorkflowsTest.php       |   5 +++++
 .../Views/ContentTranslationViewsUITest.php   |   5 +++++
 .../Functional/Views/TranslationLinkTest.php  |   5 +++++
 .../ContentTranslationContextualLinksTest.php |   5 +++++
 .../ContextualDynamicContextTest.php          |   5 +++++
 .../ContextualLinksTest.php                   |   5 +++++
 .../src/FunctionalJavascript/EditModeTest.php |   5 +++++
 .../tests/src/Functional/DateFilterTest.php   |   5 +++++
 .../src/Functional/DateTimeFieldTest.php      |   5 +++++
 .../DateTimeTimeAgoFormatterTest.php          |   5 +++++
 .../EntityTest/EntityTestDateonlyTest.php     |   5 +++++
 .../EntityTest/EntityTestDatetimeTest.php     |   5 +++++
 .../src/Functional/Views/FilterDateTest.php   |   5 +++++
 .../src/Functional/DateRangeFieldTest.php     |   5 +++++
 .../EntityTest/EntityTestDateRangeTest.php    |   5 +++++
 .../src/Functional/DbLogResourceTest.php      |   5 +++++
 .../dblog/tests/src/Functional/DbLogTest.php  |   5 +++++
 .../tests/src/Functional/DbLogViewsTest.php   |   5 +++++
 .../DynamicPageCacheIntegrationTest.php       |   5 +++++
 .../tests/src/Functional/EditorAdminTest.php  |   5 +++++
 .../src/Functional/EditorDialogAccessTest.php |   5 +++++
 .../src/Functional/EditorLoadingTest.php      |   5 +++++
 .../EditorPrivateFileReferenceFilterTest.php  |   5 +++++
 .../src/Functional/EditorSecurityTest.php     |   5 +++++
 .../Functional/EditorUploadImageScaleTest.php |   5 +++++
 .../Functional/Hal/EditorHalJsonAnonTest.php  |   5 +++++
 .../Hal/EditorHalJsonBasicAuthTest.php        |   5 +++++
 .../Hal/EditorHalJsonCookieTest.php           |   5 +++++
 .../QuickEditIntegrationLoadingTest.php       |   5 +++++
 .../Functional/Rest/EditorJsonAnonTest.php    |   5 +++++
 .../Rest/EditorJsonBasicAuthTest.php          |   5 +++++
 .../Functional/Rest/EditorJsonCookieTest.php  |   5 +++++
 .../src/Functional/Rest/EditorXmlAnonTest.php |   5 +++++
 .../Rest/EditorXmlBasicAuthTest.php           |   5 +++++
 .../Functional/Rest/EditorXmlCookieTest.php   |   5 +++++
 .../FunctionalJavascript/EditorAdminTest.php  |   5 +++++
 .../Functional/Boolean/BooleanFieldTest.php   |   5 +++++
 .../Boolean/BooleanFormatterSettingsTest.php  |   5 +++++
 .../src/Functional/Email/EmailFieldTest.php   |   5 +++++
 .../EntityReferenceAdminTest.php              |   5 +++++
 .../EntityReferenceAutoCreateTest.php         |   5 +++++
 .../EntityReferenceFieldDefaultValueTest.php  |   5 +++++
 ...erenceFieldTranslatedReferenceViewTest.php |   5 +++++
 .../EntityReferenceFileUploadTest.php         |   5 +++++
 .../EntityReferenceIntegrationTest.php        |   5 +++++
 .../EntityReferenceXSSTest.php                |   5 +++++
 .../EntityReference/Views/SelectionTest.php   |   5 +++++
 .../tests/src/Functional/FieldAccessTest.php  |   5 +++++
 .../FieldDefaultValueCallbackTest.php         |   5 +++++
 .../tests/src/Functional/FieldHelpTest.php    |   5 +++++
 .../FieldImportDeleteUninstallUiTest.php      |   5 +++++
 .../field/tests/src/Functional/FormTest.php   |   5 +++++
 .../Hal/FieldConfigHalJsonAnonTest.php        |   5 +++++
 .../Hal/FieldConfigHalJsonBasicAuthTest.php   |   5 +++++
 .../Hal/FieldConfigHalJsonCookieTest.php      |   5 +++++
 .../Hal/FieldStorageConfigHalJsonAnonTest.php |   5 +++++
 ...FieldStorageConfigHalJsonBasicAuthTest.php |   5 +++++
 .../FieldStorageConfigHalJsonCookieTest.php   |   5 +++++
 .../tests/src/Functional/NestedFormTest.php   |   5 +++++
 .../src/Functional/Number/NumberFieldTest.php |   5 +++++
 .../Rest/FieldConfigJsonAnonTest.php          |   5 +++++
 .../Rest/FieldConfigJsonBasicAuthTest.php     |   5 +++++
 .../Rest/FieldConfigJsonCookieTest.php        |   5 +++++
 .../Rest/FieldConfigXmlAnonTest.php           |   5 +++++
 .../Rest/FieldConfigXmlBasicAuthTest.php      |   5 +++++
 .../Rest/FieldConfigXmlCookieTest.php         |   5 +++++
 .../Rest/FieldStorageConfigJsonAnonTest.php   |   5 +++++
 .../FieldStorageConfigJsonBasicAuthTest.php   |   5 +++++
 .../Rest/FieldStorageConfigJsonCookieTest.php |   5 +++++
 .../Rest/FieldStorageConfigXmlAnonTest.php    |   5 +++++
 .../FieldStorageConfigXmlBasicAuthTest.php    |   5 +++++
 .../Rest/FieldStorageConfigXmlCookieTest.php  |   5 +++++
 .../src/Functional/String/StringFieldTest.php |   5 +++++
 .../src/Functional/TranslationWebTest.php     |   5 +++++
 .../src/Functional/Views/FieldUITest.php      |   5 +++++
 .../Functional/reEnableModuleFieldTest.php    |   5 +++++
 .../Boolean/BooleanFormatterSettingsTest.php  |   5 +++++
 .../EntityReferenceAdminTest.php              |   5 +++++
 .../FormJSAddMoreTest.php                     |   5 +++++
 .../Number/NumberFieldTest.php                |   5 +++++
 .../tests/src/Functional/FieldLayoutTest.php  |   5 +++++
 .../FunctionalJavascript/FieldLayoutTest.php  |   5 +++++
 .../src/Functional/EntityDisplayModeTest.php  |   5 +++++
 .../src/Functional/EntityDisplayTest.php      |   5 +++++
 .../src/Functional/FieldUIDeleteTest.php      |   5 +++++
 .../src/Functional/FieldUIIndentationTest.php |   5 +++++
 .../tests/src/Functional/FieldUIRouteTest.php |   5 +++++
 .../src/Functional/ManageDisplayTest.php      |   5 +++++
 .../Functional/ManageFieldsFunctionalTest.php |   5 +++++
 .../tests/src/Functional/ManageFieldsTest.php |   5 +++++
 .../EntityDisplayTest.php                     |   5 +++++
 .../ManageDisplayTest.php                     |   5 +++++
 .../tests/src/Functional/DownloadTest.php     |   5 +++++
 .../FileFieldAnonymousSubmissionTest.php      |   5 +++++
 .../src/Functional/FileFieldDisplayTest.php   |   5 +++++
 .../FileFieldFormatterAccessTest.php          |   5 +++++
 .../src/Functional/FileFieldPathTest.php      |   5 +++++
 .../Functional/FileFieldRSSContentTest.php    |   5 +++++
 .../src/Functional/FileFieldRevisionTest.php  |   5 +++++
 .../src/Functional/FileFieldValidateTest.php  |   5 +++++
 .../src/Functional/FileFieldWidgetTest.php    |   5 +++++
 .../tests/src/Functional/FileListingTest.php  |   5 +++++
 .../Functional/FileManagedFileElementTest.php |   5 +++++
 .../Functional/FileOnTranslatedEntityTest.php |   5 +++++
 .../tests/src/Functional/FilePrivateTest.php  |   5 +++++
 .../src/Functional/FileTokenReplaceTest.php   |   5 +++++
 .../FileUploadJsonBasicAuthTest.php           |   5 +++++
 .../Functional/FileUploadJsonCookieTest.php   |   5 +++++
 .../Formatter/FileAudioFormatterTest.php      |   5 +++++
 .../Formatter/FileVideoFormatterTest.php      |   5 +++++
 .../Functional/Hal/FileHalJsonAnonTest.php    |   5 +++++
 .../Hal/FileHalJsonBasicAuthTest.php          |   5 +++++
 .../Functional/Hal/FileHalJsonCookieTest.php  |   5 +++++
 .../Hal/FileUploadHalJsonBasicAuthTest.php    |   5 +++++
 .../Hal/FileUploadHalJsonCookieTest.php       |   5 +++++
 .../src/Functional/MultipleFileUploadTest.php |   5 +++++
 .../PrivateFileOnTranslatedEntityTest.php     |   5 +++++
 .../Functional/RemoteFileSaveUploadTest.php   |   5 +++++
 .../src/Functional/Rest/FileJsonAnonTest.php  |   5 +++++
 .../Functional/Rest/FileJsonBasicAuthTest.php |   5 +++++
 .../Functional/Rest/FileJsonCookieTest.php    |   5 +++++
 .../src/Functional/Rest/FileXmlAnonTest.php   |   5 +++++
 .../Functional/Rest/FileXmlBasicAuthTest.php  |   5 +++++
 .../src/Functional/Rest/FileXmlCookieTest.php |   5 +++++
 .../src/Functional/SaveUploadFormTest.php     |   5 +++++
 .../tests/src/Functional/SaveUploadTest.php   |   5 +++++
 .../Views/RelationshipUserFileDataTest.php    |   5 +++++
 .../AjaxFileManagedMultipleTest.php           |   5 +++++
 .../FileFieldValidateTest.php                 |   5 +++++
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 .../src/Functional/UrlAlterFunctionalTest.php |   5 +++++
 .../QuickEditCustomPipelineTest.php           |   5 +++++
 .../QuickEditEndPointAccessTest.php           |   5 +++++
 .../src/Functional/QuickEditMinimalTest.php   |   5 +++++
 .../src/FunctionalJavascript/FieldTest.php    |   5 +++++
 .../QuickEditAutocompleteTermTest.php         |   5 +++++
 .../QuickEditFileTest.php                     |   5 +++++
 .../QuickEditIntegrationTest.php              |   5 +++++
 .../QuickEditLoadingTest.php                  |   5 +++++
 .../src/Functional/CommentAttributesTest.php  |   5 +++++
 .../EntityReferenceFieldAttributesTest.php    |   5 +++++
 .../Functional/FileFieldAttributesTest.php    |   5 +++++
 .../src/Functional/GetRdfNamespacesTest.php   |   5 +++++
 .../Hal/RdfMappingHalJsonAnonTest.php         |   5 +++++
 .../Hal/RdfMappingHalJsonBasicAuthTest.php    |   5 +++++
 .../Hal/RdfMappingHalJsonCookieTest.php       |   5 +++++
 .../Functional/ImageFieldAttributesTest.php   |   5 +++++
 .../src/Functional/NodeAttributesTest.php     |   5 +++++
 .../Rest/RdfMappingJsonAnonTest.php           |   5 +++++
 .../Rest/RdfMappingJsonBasicAuthTest.php      |   5 +++++
 .../Rest/RdfMappingJsonCookieTest.php         |   5 +++++
 .../Functional/Rest/RdfMappingXmlAnonTest.php |   5 +++++
 .../Rest/RdfMappingXmlBasicAuthTest.php       |   5 +++++
 .../Rest/RdfMappingXmlCookieTest.php          |   5 +++++
 .../src/Functional/StandardProfileTest.php    |   9 +++++----
 .../src/Functional/TaxonomyAttributesTest.php |   5 +++++
 .../src/Functional/UserAttributesTest.php     |   5 +++++
 .../ResponsiveImageStyleHalJsonAnonTest.php   |   5 +++++
 ...sponsiveImageStyleHalJsonBasicAuthTest.php |   5 +++++
 .../ResponsiveImageStyleHalJsonCookieTest.php |   5 +++++
 .../Functional/ResponsiveImageAdminUITest.php |   5 +++++
 .../ResponsiveImageFieldDisplayTest.php       |   5 +++++
 .../Rest/ResponsiveImageStyleJsonAnonTest.php |   5 +++++
 .../ResponsiveImageStyleJsonBasicAuthTest.php |   5 +++++
 .../ResponsiveImageStyleJsonCookieTest.php    |   5 +++++
 .../Rest/ResponsiveImageStyleXmlAnonTest.php  |   5 +++++
 .../ResponsiveImageStyleXmlBasicAuthTest.php  |   5 +++++
 .../ResponsiveImageStyleXmlCookieTest.php     |   5 +++++
 .../src/Functional/ViewsIntegrationTest.php   |   5 +++++
 .../EntityResourceRestTestCoverageTest.php    |   5 +++++
 .../ModeratedNodeJsonAnonTest.php             |   5 +++++
 .../ModeratedNodeJsonBasicAuthTest.php        |   5 +++++
 .../ModeratedNodeJsonCookieTest.php           |   5 +++++
 .../ModeratedNodeXmlAnonTest.php              |   5 +++++
 .../ModeratedNodeXmlBasicAuthTest.php         |   5 +++++
 .../ModeratedNodeXmlCookieTest.php            |   5 +++++
 .../Hal/RestResourceConfigHalJsonAnonTest.php |   5 +++++
 ...RestResourceConfigHalJsonBasicAuthTest.php |   5 +++++
 .../RestResourceConfigHalJsonCookieTest.php   |   5 +++++
 .../tests/src/Functional/ResourceTest.php     |   5 +++++
 .../Rest/RestResourceConfigJsonAnonTest.php   |   5 +++++
 .../RestResourceConfigJsonBasicAuthTest.php   |   5 +++++
 .../Rest/RestResourceConfigJsonCookieTest.php |   5 +++++
 .../Rest/RestResourceConfigXmlAnonTest.php    |   5 +++++
 .../RestResourceConfigXmlBasicAuthTest.php    |   5 +++++
 .../Rest/RestResourceConfigXmlCookieTest.php  |   5 +++++
 .../Views/ExcludedFieldTokenTest.php          |   5 +++++
 .../src/Functional/Views/FieldCounterTest.php |   5 +++++
 .../Functional/Views/RestExportAuthTest.php   |   5 +++++
 .../Functional/Views/StyleSerializerTest.php  |   5 +++++
 .../Hal/SearchPageHalJsonAnonTest.php         |   5 +++++
 .../Hal/SearchPageHalJsonBasicAuthTest.php    |   5 +++++
 .../Hal/SearchPageHalJsonCookieTest.php       |   5 +++++
 .../Rest/SearchPageJsonAnonTest.php           |   5 +++++
 .../Rest/SearchPageJsonBasicAuthTest.php      |   5 +++++
 .../Rest/SearchPageJsonCookieTest.php         |   5 +++++
 .../Functional/Rest/SearchPageXmlAnonTest.php |   5 +++++
 .../Rest/SearchPageXmlBasicAuthTest.php       |   5 +++++
 .../Rest/SearchPageXmlCookieTest.php          |   5 +++++
 .../SearchAdvancedSearchFormTest.php          |   5 +++++
 .../tests/src/Functional/SearchBlockTest.php  |   5 +++++
 .../SearchCommentCountToggleTest.php          |   5 +++++
 .../src/Functional/SearchCommentTest.php      |   5 +++++
 .../SearchConfigSettingsFormTest.php          |   5 +++++
 .../src/Functional/SearchDateIntervalTest.php |   5 +++++
 .../src/Functional/SearchEmbedFormTest.php    |   5 +++++
 .../tests/src/Functional/SearchExactTest.php  |   5 +++++
 .../SearchKeywordsConditionsTest.php          |   5 +++++
 .../src/Functional/SearchLanguageTest.php     |   5 +++++
 .../SearchMultilingualEntityTest.php          |   5 +++++
 .../Functional/SearchNodeDiacriticsTest.php   |   5 +++++
 .../Functional/SearchNodePunctuationTest.php  |   5 +++++
 .../SearchNodeUpdateAndDeletionTest.php       |   5 +++++
 .../Functional/SearchNumberMatchingTest.php   |   5 +++++
 .../src/Functional/SearchNumbersTest.php      |   5 +++++
 .../Functional/SearchPageCacheTagsTest.php    |   5 +++++
 .../src/Functional/SearchPageOverrideTest.php |   5 +++++
 .../src/Functional/SearchPageTextTest.php     |   5 +++++
 .../SearchPreprocessLangcodeTest.php          |   5 +++++
 .../src/Functional/SearchQueryAlterTest.php   |   5 +++++
 .../src/Functional/SearchRankingTest.php      |   5 +++++
 .../src/Functional/SearchSetLocaleTest.php    |   5 +++++
 .../src/Functional/SearchSimplifyTest.php     |   5 +++++
 .../src/Functional/SearchTokenizerTest.php    |   5 +++++
 .../tests/src/Functional/SettingsTrayTest.php |   5 +++++
 .../FunctionalJavascript/ConfigAccessTest.php |   5 +++++
 .../OverriddenConfigurationTest.php           |   5 +++++
 .../QuickEditIntegrationTest.php              |   5 +++++
 .../SettingsTrayBlockFormTest.php             |   5 +++++
 .../Hal/ShortcutHalJsonAnonTest.php           |   5 +++++
 .../Hal/ShortcutHalJsonBasicAuthTest.php      |   5 +++++
 .../Hal/ShortcutHalJsonCookieTest.php         |   5 +++++
 .../Hal/ShortcutSetHalJsonAnonTest.php        |   5 +++++
 .../Hal/ShortcutSetHalJsonBasicAuthTest.php   |   5 +++++
 .../Hal/ShortcutSetHalJsonCookieTest.php      |   5 +++++
 .../Functional/Rest/ShortcutJsonAnonTest.php  |   5 +++++
 .../Rest/ShortcutJsonBasicAuthTest.php        |   5 +++++
 .../Rest/ShortcutJsonCookieTest.php           |   5 +++++
 .../Rest/ShortcutSetJsonAnonTest.php          |   5 +++++
 .../Rest/ShortcutSetJsonBasicAuthTest.php     |   5 +++++
 .../Rest/ShortcutSetJsonCookieTest.php        |   5 +++++
 .../Rest/ShortcutSetXmlAnonTest.php           |   5 +++++
 .../Rest/ShortcutSetXmlBasicAuthTest.php      |   5 +++++
 .../Rest/ShortcutSetXmlCookieTest.php         |   5 +++++
 .../Functional/Rest/ShortcutXmlAnonTest.php   |   5 +++++
 .../Rest/ShortcutXmlBasicAuthTest.php         |   5 +++++
 .../Functional/Rest/ShortcutXmlCookieTest.php |   5 +++++
 .../src/Functional/ShortcutCacheTagsTest.php  |   5 +++++
 .../src/Functional/ShortcutLinksTest.php      |   5 +++++
 .../tests/src/Functional/ShortcutSetsTest.php |   5 +++++
 .../Functional/ShortcutTranslationUITest.php  |   5 +++++
 .../tests/src/Functional/SimpletestTest.php   |   5 +++++
 .../src/Functional/StatisticsAdminTest.php    |   5 +++++
 .../src/Functional/StatisticsAttachedTest.php |   5 +++++
 .../src/Functional/StatisticsLoggingTest.php  |   5 +++++
 .../src/Functional/StatisticsReportsTest.php  |   5 +++++
 .../Functional/StatisticsTokenReplaceTest.php |   5 +++++
 .../src/Functional/Views/IntegrationTest.php  |   5 +++++
 .../StatisticsLoggingTest.php                 |   5 +++++
 .../tests/src/Functional/SyslogTest.php       |   5 +++++
 .../Hal/EntityTestBundleHalJsonAnonTest.php   |   5 +++++
 .../EntityTestBundleHalJsonBasicAuthTest.php  |   5 +++++
 .../Hal/EntityTestBundleHalJsonCookieTest.php |   5 +++++
 .../Hal/EntityTestHalJsonAnonTest.php         |   5 +++++
 .../Hal/EntityTestHalJsonBasicAuthTest.php    |   5 +++++
 .../Hal/EntityTestHalJsonCookieTest.php       |   5 +++++
 ...tHalJsonInternalPropertyNormalizerTest.php |   5 +++++
 .../Hal/EntityTestLabelHalJsonAnonTest.php    |   5 +++++
 .../EntityTestLabelHalJsonBasicAuthTest.php   |   5 +++++
 .../Hal/EntityTestLabelHalJsonCookieTest.php  |   5 +++++
 .../Hal/EntityTestMapFieldHalJsonAnonTest.php |   5 +++++
 .../Rest/EntityTestBundleJsonAnonTest.php     |   5 +++++
 .../EntityTestBundleJsonBasicAuthTest.php     |   5 +++++
 .../Rest/EntityTestBundleJsonCookieTest.php   |   5 +++++
 .../Rest/EntityTestBundleXmlAnonTest.php      |   5 +++++
 .../Rest/EntityTestBundleXmlBasicAuthTest.php |   5 +++++
 .../Rest/EntityTestBundleXmlCookieTest.php    |   5 +++++
 .../Rest/EntityTestJsonAnonTest.php           |   5 +++++
 .../Rest/EntityTestJsonBasicAuthTest.php      |   5 +++++
 .../Rest/EntityTestJsonCookieTest.php         |   5 +++++
 ...TestJsonInternalPropertyNormalizerTest.php |   5 +++++
 .../Rest/EntityTestLabelJsonAnonTest.php      |   5 +++++
 .../Rest/EntityTestLabelJsonBasicAuthTest.php |   5 +++++
 .../Rest/EntityTestLabelJsonCookieTest.php    |   5 +++++
 .../Rest/EntityTestLabelXmlAnonTest.php       |   5 +++++
 .../Rest/EntityTestLabelXmlBasicAuthTest.php  |   5 +++++
 .../Rest/EntityTestLabelXmlCookieTest.php     |   5 +++++
 .../Rest/EntityTestMapFieldJsonAnonTest.php   |   5 +++++
 .../Rest/EntityTestTextItemNormalizerTest.php |   5 +++++
 .../Functional/Rest/EntityTestXmlAnonTest.php |   5 +++++
 .../Rest/EntityTestXmlBasicAuthTest.php       |   5 +++++
 .../Rest/EntityTestXmlCookieTest.php          |   5 +++++
 .../src/Functional/Ajax/FrameworkTest.php     |   5 +++++
 .../Functional/Ajax/OffCanvasDialogTest.php   |   5 +++++
 .../tests/src/Functional/Batch/PageTest.php   |   5 +++++
 .../src/Functional/Batch/ProcessingTest.php   |   5 +++++
 .../Bootstrap/DrupalMessengerServiceTest.php  |   5 +++++
 .../tests/src/Functional/Cache/ClearTest.php  |   5 +++++
 .../Cache/SessionExistsCacheContextTest.php   |   5 +++++
 .../tests/src/Functional/Common/AlterTest.php |   5 +++++
 .../Common/EarlyRenderingControllerTest.php   |   5 +++++
 .../src/Functional/Common/FormatDateTest.php  |   5 +++++
 .../src/Functional/Common/RenderWebTest.php   |   5 +++++
 .../tests/src/Functional/Common/UrlTest.php   |   5 +++++
 .../Condition/ConditionFormTest.php           |   5 +++++
 .../src/Functional/CsrfRequestHeaderTest.php  |   5 +++++
 .../Database/SelectPagerDefaultTest.php       |   5 +++++
 .../Database/SelectTableSortDefaultTest.php   |   5 +++++
 .../Database/TemporaryQueryTest.php           |   5 +++++
 .../Datetime/DrupalDateTimeTest.php           |   5 +++++
 .../DrupalKernel/ContainerRebuildWebTest.php  |   5 +++++
 .../DrupalKernel/ContentNegotiationTest.php   |   5 +++++
 .../src/Functional/Entity/EntityAddUITest.php |   5 +++++
 .../src/Functional/Entity/EntityFormTest.php  |   5 +++++
 .../Entity/EntityListBuilderTest.php          |   5 +++++
 .../Entity/EntityOperationsTest.php           |   5 +++++
 .../Functional/Entity/EntityRevisionsTest.php |   5 +++++
 .../Entity/EntityTranslationFormTest.php      |   5 +++++
 .../Entity/EntityViewControllerTest.php       |   5 +++++
 .../UpdateApiEntityDefinitionUpdateTest.php   |   5 +++++
 .../tests/src/Functional/File/ConfigTest.php  |   5 +++++
 .../File/FileSaveHtaccessLoggingTest.php      |   5 +++++
 .../FileTransfer/FileTransferTest.php         |   5 +++++
 .../tests/src/Functional/Form/AlterTest.php   |   5 +++++
 .../Functional/Form/ArbitraryRebuildTest.php  |   5 +++++
 .../src/Functional/Form/CheckboxTest.php      |   5 +++++
 .../src/Functional/Form/ConfirmFormTest.php   |   5 +++++
 .../tests/src/Functional/Form/ElementTest.php |   5 +++++
 .../Functional/Form/ElementsAccessTest.php    |   5 +++++
 .../Functional/Form/ElementsContainerTest.php |   5 +++++
 .../Functional/Form/ElementsLabelsTest.php    |   5 +++++
 .../Form/ElementsTableSelectTest.php          |   5 +++++
 .../Form/ElementsVerticalTabsTest.php         |   5 +++++
 .../tests/src/Functional/Form/EmailTest.php   |   5 +++++
 .../src/Functional/Form/FormObjectTest.php    |   5 +++++
 .../Form/FormStoragePageCacheTest.php         |   5 +++++
 .../tests/src/Functional/Form/FormTest.php    |   5 +++++
 .../Form/LanguageSelectElementTest.php        |   5 +++++
 .../Form/ModulesListFormWebTest.php           |   5 +++++
 .../tests/src/Functional/Form/RebuildTest.php |   5 +++++
 .../src/Functional/Form/RedirectTest.php      |   5 +++++
 .../src/Functional/Form/ResponseTest.php      |   5 +++++
 .../Form/StateValuesCleanAdvancedTest.php     |   5 +++++
 .../Functional/Form/StateValuesCleanTest.php  |   5 +++++
 .../tests/src/Functional/Form/StorageTest.php |   5 +++++
 .../Functional/Form/SystemConfigFormTest.php  |   5 +++++
 .../tests/src/Functional/Form/UrlTest.php     |   5 +++++
 .../src/Functional/Form/ValidationTest.php    |   5 +++++
 .../Functional/Hal/ActionHalJsonAnonTest.php  |   5 +++++
 .../Hal/ActionHalJsonBasicAuthTest.php        |   5 +++++
 .../Hal/ActionHalJsonCookieTest.php           |   5 +++++
 .../Functional/Hal/MenuHalJsonAnonTest.php    |   5 +++++
 .../Hal/MenuHalJsonBasicAuthTest.php          |   5 +++++
 .../Functional/Hal/MenuHalJsonCookieTest.php  |   5 +++++
 .../Functional/Lock/LockFunctionalTest.php    |   5 +++++
 .../src/Functional/Mail/HtmlToTextTest.php    |   5 +++++
 .../Menu/BreadcrumbFrontCacheContextsTest.php |   5 +++++
 .../src/Functional/Menu/LocalActionTest.php   |   5 +++++
 .../src/Functional/Menu/LocalTasksTest.php    |   5 +++++
 .../src/Functional/Menu/MenuAccessTest.php    |   5 +++++
 .../Functional/Menu/MenuLinkSecurityTest.php  |   5 +++++
 .../src/Functional/Menu/MenuRouterTest.php    |  10 ++++------
 .../src/Functional/Module/ClassLoaderTest.php |   5 +++++
 .../src/Functional/Module/DependencyTest.php  |   5 +++++
 .../Module/ExperimentalModuleTest.php         |   5 +++++
 .../Module/HookRequirementsTest.php           |   5 +++++
 .../src/Functional/Module/InstallTest.php     |   5 +++++
 .../Module/InstallUninstallTest.php           |   5 +++++
 .../Module/PrepareUninstallTest.php           |   5 +++++
 .../src/Functional/Module/UninstallTest.php   |   5 +++++
 .../src/Functional/Module/VersionTest.php     |   5 +++++
 .../Functional/Page/DefaultMetatagsTest.php   |   5 +++++
 .../tests/src/Functional/Pager/PagerTest.php  |   5 +++++
 .../ParamConverter/UpcastingTest.php          |   5 +++++
 .../Functional/Render/AjaxPageStateTest.php   |   5 +++++
 .../Functional/Render/DisplayVariantTest.php  |   5 +++++
 .../Render/HtmlResponseAttachmentsTest.php    |   5 +++++
 .../Render/PlaceholderMessageTest.php         |   5 +++++
 .../RenderArrayNonHtmlSubscriberTest.php      |   5 +++++
 .../UrlBubbleableMetadataBubblingTest.php     |   5 +++++
 .../Functional/Rest/ActionJsonAnonTest.php    |   5 +++++
 .../Rest/ActionJsonBasicAuthTest.php          |   5 +++++
 .../Functional/Rest/ActionJsonCookieTest.php  |   5 +++++
 .../src/Functional/Rest/ActionXmlAnonTest.php |   5 +++++
 .../Rest/ActionXmlBasicAuthTest.php           |   5 +++++
 .../Functional/Rest/ActionXmlCookieTest.php   |   5 +++++
 .../src/Functional/Rest/MenuJsonAnonTest.php  |   5 +++++
 .../Functional/Rest/MenuJsonBasicAuthTest.php |   5 +++++
 .../Functional/Rest/MenuJsonCookieTest.php    |   5 +++++
 .../src/Functional/Rest/MenuXmlAnonTest.php   |   5 +++++
 .../Functional/Rest/MenuXmlBasicAuthTest.php  |   5 +++++
 .../src/Functional/Rest/MenuXmlCookieTest.php |   5 +++++
 .../Functional/Routing/DestinationTest.php    |   5 +++++
 .../Routing/RouterPermissionTest.php          |   5 +++++
 .../src/Functional/Routing/RouterTest.php     |   5 +++++
 .../ServiceProviderWebTest.php                |   5 +++++
 .../Session/SessionAuthenticationTest.php     |   5 +++++
 .../Functional/Session/SessionHttpsTest.php   |   5 +++++
 .../src/Functional/Session/SessionTest.php    |   5 +++++
 .../StackSessionHandlerIntegrationTest.php    |   5 +++++
 .../Functional/System/AccessDeniedTest.php    |   5 +++++
 .../Functional/System/AdminMetaTagTest.php    |   5 +++++
 .../tests/src/Functional/System/AdminTest.php |   5 +++++
 .../src/Functional/System/CronRunTest.php     |   5 +++++
 .../System/DateFormatsLockedTest.php          |   5 +++++
 .../System/DateFormatsMachineNameTest.php     |   5 +++++
 .../src/Functional/System/DateTimeTest.php    |   5 +++++
 .../System/DefaultMobileMetaTagsTest.php      |   5 +++++
 .../Functional/System/ErrorHandlerTest.php    |   5 +++++
 .../src/Functional/System/FrontPageTest.php   |   5 +++++
 .../src/Functional/System/HtaccessTest.php    |   5 +++++
 .../src/Functional/System/IndexPhpTest.php    |   5 +++++
 .../System/MainContentFallbackTest.php        |   5 +++++
 .../Functional/System/PageNotFoundTest.php    |   5 +++++
 .../src/Functional/System/PageTitleTest.php   |   5 +++++
 .../System/ResponseGeneratorTest.php          |   5 +++++
 .../Functional/System/RetrieveFileTest.php    |   5 +++++
 .../System/ShutdownFunctionsTest.php          |   5 +++++
 .../Functional/System/SiteMaintenanceTest.php |   5 +++++
 .../System/SitesDirectoryHardeningTest.php    |   5 +++++
 .../src/Functional/System/StatusTest.php      |   5 +++++
 .../Functional/System/SystemAuthorizeTest.php |   5 +++++
 .../tests/src/Functional/System/ThemeTest.php |   5 +++++
 .../Functional/System/TokenReplaceWebTest.php |   5 +++++
 .../src/Functional/System/TokenScanTest.php   |   5 +++++
 .../Functional/System/TrustedHostsTest.php    |   5 +++++
 .../Functional/Theme/EngineNyanCatTest.php    |   5 +++++
 .../src/Functional/Theme/EngineTwigTest.php   |   5 +++++
 .../Theme/EntityFilteringThemeTest.php        |   5 +++++
 .../Theme/ExperimentalThemeTest.php           |   5 +++++
 .../tests/src/Functional/Theme/FastTest.php   |   5 +++++
 .../Functional/Theme/HtmlAttributesTest.php   |   5 +++++
 .../Theme/ThemeEarlyInitializationTest.php    |   5 +++++
 .../src/Functional/Theme/ThemeInfoTest.php    |   5 +++++
 .../Theme/ThemeSuggestionsAlterTest.php       |   5 +++++
 .../tests/src/Functional/Theme/ThemeTest.php  |   5 +++++
 .../src/Functional/Theme/ThemeTokenTest.php   |   5 +++++
 .../Functional/Theme/TwigDebugMarkupTest.php  |   5 +++++
 .../Functional/Theme/TwigEnvironmentTest.php  |   5 +++++
 .../Functional/Theme/TwigExtensionTest.php    |   5 +++++
 .../src/Functional/Theme/TwigLoaderTest.php   |   5 +++++
 .../Theme/TwigRegistryLoaderTest.php          |   5 +++++
 .../src/Functional/Theme/TwigSettingsTest.php |   5 +++++
 .../src/Functional/Theme/TwigTransTest.php    |   5 +++++
 .../Update/AdminThemeUpdateTest.php           |   5 +++++
 ...tomatedCronUpdateWithAutomatedCronTest.php |   5 +++++
 ...atedCronUpdateWithoutAutomatedCronTest.php |   5 +++++
 .../Update/BrokenCacheUpdateTest.php          |   5 +++++
 .../Update/ConfigOverridesUpdateTest.php      |   5 +++++
 .../Update/DependencyHookInvocationTest.php   |   5 +++++
 .../Update/DependencyMissingTest.php          |   5 +++++
 .../Update/DependencyOrderingTest.php         |   5 +++++
 .../EntityUpdateAddRevisionDefaultTest.php    |   5 +++++
 ...dateAddRevisionTranslationAffectedTest.php |   5 +++++
 .../Update/EntityUpdateInitialTest.php        |   5 +++++
 .../Update/EntityUpdateToPublishableTest.php  |   5 +++++
 .../FieldSchemaDataUninstallUpdateTest.php    |   5 +++++
 .../Update/FilterHtmlUpdateTest.php           |   5 +++++
 .../InstallProfileSystemInstall8300Test.php   |   5 +++++
 .../Update/InvalidUpdateHookTest.php          |   5 +++++
 ...sAndTasksConvertedIntoBlocksUpdateTest.php |   5 +++++
 .../Update/MenuBlockPostUpdateTest.php        |   5 +++++
 .../MenuTreeSerializationTitleFilledTest.php  |   5 +++++
 .../Update/MenuTreeSerializationTitleTest.php |   5 +++++
 .../Update/MoveActionsToCoreTest.php          |   5 +++++
 .../Update/NoDependenciesUpdateTest.php       |   5 +++++
 .../PageTitleConvertedIntoBlockUpdateTest.php |   5 +++++
 .../Update/PathAliasToEntityUpdateTest.php    |   5 +++++
 .../Functional/Update/RebuildScriptTest.php   |   5 +++++
 .../Update/RecalculatedDependencyTest.php     |   5 +++++
 ...FromSystemPerformanceConfigurationTest.php |   5 +++++
 .../RouterIndexOptimizationFilledTest.php     |   5 +++++
 .../Update/RouterIndexOptimizationTest.php    |   5 +++++
 ...LocalTasksConvertedIntoBlockUpdateTest.php |   5 +++++
 ...teBrandingConvertedIntoBlockUpdateTest.php |   5 +++++
 .../Update/StableBaseThemeUpdateTest.php      |   5 +++++
 .../UpdateActionsWithEntityPluginsTest.php    |   5 +++++
 .../src/Functional/Update/UpdateCacheTest.php |   5 +++++
 .../Update/UpdateEntityDisplayTest.php        |   5 +++++
 .../Update/UpdatePathNewDependencyTest.php    |   5 +++++
 .../UpdatePathRC1TestBaseFilledTest.php       |   5 +++++
 .../Update/UpdatePathRC1TestBaseTest.php      |   5 +++++
 .../Update/UpdatePathTestBaseFilledTest.php   |   5 +++++
 .../Update/UpdatePathTestJavaScriptTest.php   |   5 +++++
 .../UpdatePathWithBrokenRoutingFilledTest.php |   5 +++++
 .../UpdatePathWithBrokenRoutingTest.php       |   5 +++++
 .../Update/UpdatePostUpdateFailingTest.php    |   5 +++++
 .../Update/UpdatePostUpdateTest.php           |   5 +++++
 .../Functional/Update/UpdateSchemaTest.php    |   5 +++++
 .../Functional/Update/UpdateScriptTest.php    |   5 +++++
 .../Functional/Update/UpdatesWith7xTest.php   |   5 +++++
 .../Form/ElementsTableSelectTest.php          |   5 +++++
 .../FunctionalJavascript/Form/RebuildTest.php |   5 +++++
 .../Form/TriggeringElementTest.php            |   5 +++++
 .../FunctionalJavascript/FrameworkTest.php    |   5 +++++
 .../ModalRendererTest.php                     |   5 +++++
 .../FunctionalJavascript/OffCanvasTest.php    |   5 +++++
 .../System/DateFormatTest.php                 |   5 +++++
 .../ThemeSettingsFormTest.php                 |   5 +++++
 .../tests/src/Functional/EarlyDateTest.php    |   5 +++++
 .../Functional/Hal/TermHalJsonAnonTest.php    |   5 +++++
 .../Hal/TermHalJsonBasicAuthTest.php          |   5 +++++
 .../Functional/Hal/TermHalJsonCookieTest.php  |   5 +++++
 .../Hal/VocabularyHalJsonAnonTest.php         |   5 +++++
 .../Hal/VocabularyHalJsonBasicAuthTest.php    |   5 +++++
 .../Hal/VocabularyHalJsonCookieTest.php       |   5 +++++
 .../tests/src/Functional/LoadMultipleTest.php |   5 +++++
 .../src/Functional/Rest/TermJsonAnonTest.php  |   5 +++++
 .../Functional/Rest/TermJsonBasicAuthTest.php |   5 +++++
 .../Functional/Rest/TermJsonCookieTest.php    |   5 +++++
 .../src/Functional/Rest/TermXmlAnonTest.php   |   5 +++++
 .../Functional/Rest/TermXmlBasicAuthTest.php  |   5 +++++
 .../src/Functional/Rest/TermXmlCookieTest.php |   5 +++++
 .../Rest/VocabularyJsonAnonTest.php           |   5 +++++
 .../Rest/VocabularyJsonBasicAuthTest.php      |   5 +++++
 .../Rest/VocabularyJsonCookieTest.php         |   5 +++++
 .../Functional/Rest/VocabularyXmlAnonTest.php |   5 +++++
 .../Rest/VocabularyXmlBasicAuthTest.php       |   5 +++++
 .../Rest/VocabularyXmlCookieTest.php          |   5 +++++
 .../taxonomy/tests/src/Functional/RssTest.php |   5 +++++
 .../src/Functional/TaxonomyImageTest.php      |   5 +++++
 .../TaxonomyTermIndentationTest.php           |   5 +++++
 .../src/Functional/TaxonomyTermPagerTest.php  |   5 +++++
 .../tests/src/Functional/TermAccessTest.php   |   5 +++++
 .../src/Functional/TermAutocompleteTest.php   |   5 +++++
 .../src/Functional/TermCacheTagsTest.php      |   5 +++++
 .../Functional/TermContextualLinksTest.php    |   5 +++++
 .../tests/src/Functional/TermIndexTest.php    |   5 +++++
 .../tests/src/Functional/TermLanguageTest.php |   5 +++++
 .../tests/src/Functional/TermTest.php         |   5 +++++
 .../TermTranslationFieldViewTest.php          |   5 +++++
 .../src/Functional/TermTranslationTest.php    |   5 +++++
 .../src/Functional/TermTranslationUITest.php  |   5 +++++
 .../tests/src/Functional/ThemeTest.php        |   5 +++++
 .../tests/src/Functional/TokenReplaceTest.php |   5 +++++
 .../Views/RelationshipNodeTermDataTest.php    |   5 +++++
 .../RelationshipRepresentativeNodeTest.php    |   5 +++++
 .../Views/TaxonomyDefaultArgumentTest.php     |   5 +++++
 .../Views/TaxonomyFieldAllTermsTest.php       |   5 +++++
 .../Views/TaxonomyFieldFilterTest.php         |   5 +++++
 .../Views/TaxonomyIndexTidUiTest.php          |   5 +++++
 .../Functional/Views/TaxonomyParentUITest.php |   5 +++++
 .../Views/TaxonomyRelationshipTest.php        |   5 +++++
 .../Views/TaxonomyTermArgumentDepthTest.php   |   5 +++++
 .../Views/TaxonomyTermFilterDepthTest.php     |   5 +++++
 .../Functional/Views/TaxonomyTermViewTest.php |   5 +++++
 .../Views/TaxonomyVocabularyArgumentTest.php  |   5 +++++
 .../Views/TermDisplayConfigurableTest.php     |   5 +++++
 .../Functional/Views/TermNameFieldTest.php    |   5 +++++
 .../src/Functional/VocabularyLanguageTest.php |   5 +++++
 .../Functional/VocabularyPermissionsTest.php  |   5 +++++
 .../VocabularySerializationTest.php           |   5 +++++
 .../Functional/VocabularyTranslationTest.php  |   5 +++++
 .../tests/src/Functional/VocabularyUiTest.php |   5 +++++
 .../src/Functional/TelephoneFieldTest.php     |   5 +++++
 .../tests/src/Functional/TextFieldTest.php    |   5 +++++
 .../TextRequiredSummaryUpdateTest.php         |   5 +++++
 .../TextareaWithSummaryTest.php               |   5 +++++
 .../src/Functional/ToolbarAdminMenuTest.php   |   5 +++++
 .../Functional/ToolbarCacheContextsTest.php   |   5 +++++
 .../src/Functional/ToolbarHookToolbarTest.php |   5 +++++
 .../Functional/ToolbarMenuTranslationTest.php |   5 +++++
 .../ToolbarIntegrationTest.php                |   5 +++++
 .../Functional/Hal/TourHalJsonAnonTest.php    |   5 +++++
 .../Hal/TourHalJsonBasicAuthTest.php          |   5 +++++
 .../Functional/Hal/TourHalJsonCookieTest.php  |   5 +++++
 .../src/Functional/Rest/TourJsonAnonTest.php  |   5 +++++
 .../Functional/Rest/TourJsonBasicAuthTest.php |   5 +++++
 .../Functional/Rest/TourJsonCookieTest.php    |   5 +++++
 .../src/Functional/Rest/TourXmlAnonTest.php   |   5 +++++
 .../Functional/Rest/TourXmlBasicAuthTest.php  |   5 +++++
 .../src/Functional/Rest/TourXmlCookieTest.php |   5 +++++
 .../src/Functional/TourCacheTagsTest.php      |   5 +++++
 .../tests/src/Functional/TourHelpPageTest.php |   5 +++++
 .../tour/tests/src/Functional/TourTest.php    |   5 +++++
 .../src/Functional/TrackerNodeAccessTest.php  |   5 +++++
 .../tests/src/Functional/TrackerTest.php      |   5 +++++
 .../FileTransferAuthorizeFormTest.php         |   5 +++++
 .../src/Functional/UpdateContribTest.php      |   5 +++++
 .../tests/src/Functional/UpdateCoreTest.php   |   5 +++++
 .../tests/src/Functional/UpdateUploadTest.php |   5 +++++
 .../tests/src/Functional/AccessRoleUITest.php |   5 +++++
 .../Functional/Hal/RoleHalJsonAnonTest.php    |   5 +++++
 .../Hal/RoleHalJsonBasicAuthTest.php          |   5 +++++
 .../Functional/Hal/RoleHalJsonCookieTest.php  |   5 +++++
 .../Functional/Hal/UserHalJsonAnonTest.php    |   5 +++++
 .../Hal/UserHalJsonBasicAuthTest.php          |   5 +++++
 .../Functional/Hal/UserHalJsonCookieTest.php  |   5 +++++
 .../src/Functional/Rest/RoleJsonAnonTest.php  |   5 +++++
 .../Functional/Rest/RoleJsonBasicAuthTest.php |   5 +++++
 .../Functional/Rest/RoleJsonCookieTest.php    |   5 +++++
 .../src/Functional/Rest/RoleXmlAnonTest.php   |   5 +++++
 .../Functional/Rest/RoleXmlBasicAuthTest.php  |   5 +++++
 .../src/Functional/Rest/RoleXmlCookieTest.php |   5 +++++
 .../src/Functional/Rest/UserJsonAnonTest.php  |   5 +++++
 .../Functional/Rest/UserJsonBasicAuthTest.php |   5 +++++
 .../Functional/Rest/UserJsonCookieTest.php    |   5 +++++
 .../src/Functional/Rest/UserXmlAnonTest.php   |   5 +++++
 .../Functional/Rest/UserXmlBasicAuthTest.php  |   5 +++++
 .../src/Functional/Rest/UserXmlCookieTest.php |   5 +++++
 .../src/Functional/RestRegisterUserTest.php   |   5 +++++
 .../src/Functional/UserAccountLinksTest.php   |   5 +++++
 .../src/Functional/UserAdminLanguageTest.php  |   5 +++++
 .../src/Functional/UserAdminListingTest.php   |   5 +++++
 .../tests/src/Functional/UserAdminTest.php    |   5 +++++
 .../tests/src/Functional/UserBlocksTest.php   |   5 +++++
 .../src/Functional/UserCacheTagsTest.php      |   5 +++++
 .../tests/src/Functional/UserCancelTest.php   |   5 +++++
 .../src/Functional/UserCreateFailMailTest.php |   5 +++++
 .../tests/src/Functional/UserCreateTest.php   |   5 +++++
 .../tests/src/Functional/UserEditTest.php     |   5 +++++
 .../Functional/UserEditedOwnAccountTest.php   |   5 +++++
 .../Functional/UserLanguageCreationTest.php   |   5 +++++
 .../tests/src/Functional/UserLanguageTest.php |   5 +++++
 .../src/Functional/UserLoginHttpTest.php      |   5 +++++
 .../tests/src/Functional/UserLoginTest.php    |   5 +++++
 .../src/Functional/UserPasswordResetTest.php  |   5 +++++
 .../src/Functional/UserPermissionsTest.php    |   5 +++++
 .../tests/src/Functional/UserPictureTest.php  |   5 +++++
 .../src/Functional/UserRegistrationTest.php   |   5 +++++
 .../src/Functional/UserRoleAdminTest.php      |   5 +++++
 .../Functional/UserRolesAssignmentTest.php    |   5 +++++
 .../tests/src/Functional/UserSearchTest.php   |   5 +++++
 .../tests/src/Functional/UserSubAdminTest.php |   5 +++++
 .../tests/src/Functional/UserTimeZoneTest.php |   5 +++++
 .../src/Functional/UserTokenReplaceTest.php   |   5 +++++
 .../src/Functional/UserTranslationUITest.php  |   5 +++++
 .../src/Functional/Views/AccessRoleTest.php   |   5 +++++
 .../Functional/Views/BulkFormAccessTest.php   |   5 +++++
 .../src/Functional/Views/BulkFormTest.php     |   5 +++++
 .../Views/FilterPermissionUiTest.php          |   5 +++++
 .../Functional/Views/HandlerFieldRoleTest.php |   5 +++++
 .../Views/HandlerFieldUserNameTest.php        |   5 +++++
 .../Views/HandlerFilterUserNameTest.php       |   5 +++++
 .../Functional/Views/RolesRidArgumentTest.php |   5 +++++
 .../src/Functional/Views/UserChangedTest.php  |   5 +++++
 .../Views/UserFieldsAccessChangeTest.php      |   5 +++++
 .../RegistrationWithUserFieldsTest.php        |   5 +++++
 .../tests/src/Functional/BulkFormTest.php     |   5 +++++
 .../tests/src/Functional/DefaultViewsTest.php |   5 +++++
 .../Functional/Entity/BaseFieldAccessTest.php |   5 +++++
 .../Entity/EntityQueryAccessTest.php          |   5 +++++
 .../src/Functional/Entity/FieldEntityTest.php |   5 +++++
 .../Entity/FieldEntityTranslationTest.php     |   5 +++++
 .../FieldRenderedEntityTranslationTest.php    |   5 +++++
 .../Entity/ViewNonTranslatableEntityTest.php  |   5 +++++
 .../tests/src/Functional/GlossaryTest.php     |   5 +++++
 .../Functional/Hal/ViewHalJsonAnonTest.php    |   5 +++++
 .../Hal/ViewHalJsonBasicAuthTest.php          |   5 +++++
 .../Functional/Hal/ViewHalJsonCookieTest.php  |   5 +++++
 .../Handler/AreaHTTPStatusCodeTest.php        |   5 +++++
 .../tests/src/Functional/Handler/AreaTest.php |   5 +++++
 .../Functional/Handler/AreaTitleWebTest.php   |   5 +++++
 .../Handler/FieldDropButtonTest.php           |   5 +++++
 .../Handler/FieldEntityLinkBaseTest.php       |   5 +++++
 .../Handler/FieldEntityOperationsTest.php     |   5 +++++
 .../Handler/FieldGroupRowsWebTest.php         |   5 +++++
 .../src/Functional/Handler/FieldWebTest.php   |   5 +++++
 .../src/Functional/Handler/FilterDateTest.php |   5 +++++
 .../Handler/FilterPlaceholderTextTest.php     |   5 +++++
 .../src/Functional/Handler/HandlerAllTest.php |   5 +++++
 .../src/Functional/Handler/HandlerTest.php    |   5 +++++
 .../src/Functional/Plugin/AccessTest.php      |   5 +++++
 .../Functional/Plugin/ArgumentDefaultTest.php |   5 +++++
 .../src/Functional/Plugin/CacheTagTest.php    |   5 +++++
 .../src/Functional/Plugin/CacheWebTest.php    |   5 +++++
 .../ContextualFiltersBlockContextTest.php     |   5 +++++
 .../Functional/Plugin/DisabledDisplayTest.php |   5 +++++
 .../Plugin/DisplayAttachmentTest.php          |   5 +++++
 .../Plugin/DisplayEntityReferenceTest.php     |   5 +++++
 .../src/Functional/Plugin/DisplayFeedTest.php |   5 +++++
 .../Functional/Plugin/DisplayPageWebTest.php  |   5 +++++
 .../src/Functional/Plugin/DisplayTest.php     |   5 +++++
 .../Plugin/ExposedFormCheckboxesTest.php      |   5 +++++
 .../src/Functional/Plugin/ExposedFormTest.php |   5 +++++
 .../src/Functional/Plugin/FilterTest.php      |   5 +++++
 .../src/Functional/Plugin/MenuLinkTest.php    |   5 +++++
 .../src/Functional/Plugin/MiniPagerTest.php   |   5 +++++
 .../Plugin/NumericFormatPluralTest.php        |   5 +++++
 .../tests/src/Functional/Plugin/PagerTest.php |   5 +++++
 .../src/Functional/Plugin/StyleOpmlTest.php   |   5 +++++
 .../Functional/Plugin/StyleSummaryTest.php    |   5 +++++
 .../src/Functional/Plugin/StyleTableTest.php  |   5 +++++
 .../src/Functional/Plugin/ViewsBulkTest.php   |   5 +++++
 .../src/Functional/Plugin/ViewsFormTest.php   |   5 +++++
 .../src/Functional/RenderCacheWebTest.php     |   5 +++++
 .../src/Functional/Rest/ViewJsonAnonTest.php  |   5 +++++
 .../Functional/Rest/ViewJsonBasicAuthTest.php |   5 +++++
 .../Functional/Rest/ViewJsonCookieTest.php    |   5 +++++
 .../src/Functional/Rest/ViewXmlAnonTest.php   |   5 +++++
 .../Functional/Rest/ViewXmlBasicAuthTest.php  |   5 +++++
 .../src/Functional/Rest/ViewXmlCookieTest.php |   5 +++++
 .../src/Functional/SearchIntegrationTest.php  |   5 +++++
 .../src/Functional/SearchMultilingualTest.php |   5 +++++
 .../src/Functional/TaxonomyGlossaryTest.php   |   5 +++++
 .../src/Functional/UserBatchActionTest.php    |   5 +++++
 .../tests/src/Functional/UserPathTest.php     |   5 +++++
 .../tests/src/Functional/ViewAjaxTest.php     |   5 +++++
 .../tests/src/Functional/ViewElementTest.php  |   5 +++++
 .../src/Functional/ViewsEscapingTest.php      |   5 +++++
 .../src/Functional/ViewsFormMultipleTest.php  |   5 +++++
 .../Functional/ViewsNoResultsBehaviorTest.php |   5 +++++
 .../Functional/ViewsThemeIntegrationTest.php  |   5 +++++
 .../tests/src/Functional/Wizard/BasicTest.php |   5 +++++
 .../Wizard/EntityTestRevisionTest.php         |   5 +++++
 .../Functional/Wizard/ItemsPerPageTest.php    |   5 +++++
 .../tests/src/Functional/Wizard/MenuTest.php  |   5 +++++
 .../src/Functional/Wizard/NodeWizardTest.php  |   5 +++++
 .../tests/src/Functional/Wizard/PagerTest.php |   5 +++++
 .../src/Functional/Wizard/SortingTest.php     |   5 +++++
 .../src/Functional/Wizard/TaggedWithTest.php  |   5 +++++
 .../BlockExposedFilterAJAXTest.php            |   5 +++++
 .../ClickSortingAJAXTest.php                  |   5 +++++
 .../ExposedFilterAJAXTest.php                 |   5 +++++
 .../FunctionalJavascript/GlossaryViewTest.php |   5 +++++
 .../PaginationAJAXTest.php                    |   5 +++++
 .../views/Handler/ContextualFilterTest.php    |   5 +++++
 .../Plugin/views/Handler/FieldTest.php        |   5 +++++
 .../Handler/GroupedExposedFilterTest.php      |   5 +++++
 .../tests/src/Functional/AnalyzeTest.php      |   5 +++++
 .../tests/src/Functional/AreaEntityUITest.php |   5 +++++
 .../src/Functional/ArgumentValidatorTest.php  |   5 +++++
 .../tests/src/Functional/CachedDataUITest.php |   5 +++++
 .../src/Functional/CustomBooleanTest.php      |   5 +++++
 .../tests/src/Functional/DefaultViewsTest.php |   5 +++++
 .../src/Functional/DisplayAttachmentTest.php  |   5 +++++
 .../tests/src/Functional/DisplayCRUDTest.php  |   5 +++++
 .../src/Functional/DisplayExtenderUITest.php  |   5 +++++
 .../tests/src/Functional/DisplayFeedTest.php  |   5 +++++
 .../tests/src/Functional/DisplayPathTest.php  |   5 +++++
 .../tests/src/Functional/DisplayTest.php      |   5 +++++
 .../tests/src/Functional/DuplicateTest.php    |   5 +++++
 .../src/Functional/ExposedFormUITest.php      |   5 +++++
 .../tests/src/Functional/FieldUITest.php      |   5 +++++
 .../src/Functional/FilterBooleanWebTest.php   |   5 +++++
 .../src/Functional/FilterNumericWebTest.php   |   5 +++++
 .../tests/src/Functional/FilterUITest.php     |   5 +++++
 .../tests/src/Functional/GroupByTest.php      |   5 +++++
 .../tests/src/Functional/HandlerTest.php      |   5 +++++
 .../Functional/NewViewConfigSchemaTest.php    |   5 +++++
 .../src/Functional/OverrideDisplaysTest.php   |   5 +++++
 .../tests/src/Functional/PreviewTest.php      |   5 +++++
 .../tests/src/Functional/QueryTest.php        |   5 +++++
 .../src/Functional/RearrangeFieldsTest.php    |   5 +++++
 .../tests/src/Functional/RedirectTest.php     |   5 +++++
 .../tests/src/Functional/ReportFieldsTest.php |   5 +++++
 .../tests/src/Functional/ReportTest.php       |   5 +++++
 .../tests/src/Functional/RowUITest.php        |   5 +++++
 .../tests/src/Functional/SettingsTest.php     |   5 +++++
 .../tests/src/Functional/StorageTest.php      |   5 +++++
 .../tests/src/Functional/StyleTableTest.php   |   5 +++++
 .../tests/src/Functional/StyleUITest.php      |   5 +++++
 .../src/Functional/TokenizeAreaUITest.php     |   5 +++++
 .../src/Functional/TranslatedViewTest.php     |   5 +++++
 .../src/Functional/UnsavedPreviewTest.php     |   5 +++++
 .../tests/src/Functional/ViewEditTest.php     |   5 +++++
 .../tests/src/Functional/ViewsListTest.php    |   5 +++++
 .../tests/src/Functional/ViewsUITourTest.php  |   5 +++++
 .../tests/src/Functional/WizardTest.php       |   5 +++++
 .../views_ui/tests/src/Functional/XssTest.php |   5 +++++
 .../src/FunctionalJavascript/DisplayTest.php  |   5 +++++
 .../FilterCriteriaTest.php                    |   5 +++++
 .../FilterOptionsTest.php                     |   5 +++++
 .../LibraryCachingTest.php                    |   5 +++++
 .../src/FunctionalJavascript/PreviewTest.php  |   5 +++++
 .../FunctionalJavascript/ViewsListingTest.php |   5 +++++
 .../FunctionalJavascript/ViewsWizardTest.php  |   5 +++++
 .../Hal/WorkflowHalJsonAnonTest.php           |   5 +++++
 .../Hal/WorkflowHalJsonBasicAuthTest.php      |   5 +++++
 .../Hal/WorkflowHalJsonCookieTest.php         |   5 +++++
 .../Functional/Rest/WorkflowJsonAnonTest.php  |   5 +++++
 .../Rest/WorkflowJsonBasicAuthTest.php        |   5 +++++
 .../Rest/WorkflowJsonCookieTest.php           |   5 +++++
 .../Functional/Rest/WorkflowXmlAnonTest.php   |   5 +++++
 .../Rest/WorkflowXmlBasicAuthTest.php         |   5 +++++
 .../Functional/Rest/WorkflowXmlCookieTest.php |   5 +++++
 ...orkflowCustomStateTransitionAccessTest.php |   5 +++++
 .../src/Functional/WorkflowUiNoTypeTest.php   |   5 +++++
 .../tests/src/Functional/WorkflowUiTest.php   |   5 +++++
 .../EntityResource/WorkspaceJsonAnonTest.php  |   5 +++++
 .../WorkspaceJsonBasicAuthTest.php            |   5 +++++
 .../WorkspaceJsonCookieTest.php               |   5 +++++
 .../EntityResource/WorkspaceXmlAnonTest.php   |   5 +++++
 .../WorkspaceXmlBasicAuthTest.php             |   5 +++++
 .../EntityResource/WorkspaceXmlCookieTest.php |   5 +++++
 .../src/Functional/PathWorkspacesTest.php     |   5 +++++
 .../src/Functional/WorkspaceBypassTest.php    |   5 +++++
 .../Functional/WorkspaceCacheContextTest.php  |   5 +++++
 .../WorkspaceConcurrentEditingTest.php        |   5 +++++
 .../Functional/WorkspacePermissionsTest.php   |   5 +++++
 .../src/Functional/WorkspaceSwitcherTest.php  |   5 +++++
 .../tests/src/Functional/WorkspaceTest.php    |   5 +++++
 .../src/Functional/WorkspaceViewTest.php      |   5 +++++
 .../Functional/WorkspacesUninstallTest.php    |   5 +++++
 .../WorkspaceToolbarIntegrationTest.php       |   5 +++++
 .../DefaultContentFilesAccessTest.php         |   5 +++++
 .../tests/src/Functional/MinimalTest.php      |   5 +++++
 .../Ajax/AjaxCallbacksTest.php                |   5 +++++
 .../Ajax/AjaxFormCacheTest.php                |   5 +++++
 .../Ajax/AjaxFormImageButtonTest.php          |   5 +++++
 .../Ajax/AjaxFormPageCacheTest.php            |   5 +++++
 .../Ajax/AjaxInGroupTest.php                  |   5 +++++
 .../Ajax/AjaxTest.php                         |   5 +++++
 .../Ajax/BackwardCompatibilityTest.php        |   5 +++++
 .../Ajax/CommandsTest.php                     |   5 +++++
 .../Ajax/DialogTest.php                       |   5 +++++
 .../Ajax/ElementValidationTest.php            |   5 +++++
 .../Ajax/FormValuesTest.php                   |   5 +++++
 .../Ajax/MessageCommandTest.php               |   5 +++++
 .../Ajax/MultiFormTest.php                    |   5 +++++
 .../Ajax/ThrobberTest.php                     |   5 +++++
 .../BrowserWithJavascriptTest.php             |   5 +++++
 .../Core/Form/FormGroupingElementsTest.php    |   5 +++++
 .../Core/JsMessageTest.php                    |   5 +++++
 .../Core/MachineNameTest.php                  |   5 +++++
 .../Core/Session/SessionTest.php              |   5 +++++
 .../Dialog/DialogPositionTest.php             |   5 +++++
 .../EntityReferenceAutocompleteWidgetTest.php |   5 +++++
 .../JavascriptGetDrupalSettingsTest.php       |   5 +++++
 .../TableDrag/TableDragTest.php               |   5 +++++
 .../Tests/DrupalSelenium2DriverTest.php       |   5 +++++
 .../Tests/JSWebAssertTest.php                 |   5 +++++
 .../Tests/JSWebWithWebDriverAssertTest.php    |   5 +++++
 .../Bootstrap/UncaughtExceptionTest.php       |   5 +++++
 .../Breadcrumb/Breadcrumb404Test.php          |   5 +++++
 .../FunctionalTests/BrowserTestBaseTest.php   |   5 +++++
 .../BrowserTestBaseUserAgentTest.php          |   5 +++++
 .../Core/Config/SchemaConfigListenerTest.php  |   5 +++++
 .../Core/Test/ModuleInstallBatchTest.php      |   5 +++++
 .../Datetime/TimestampAgoFormatterTest.php    |   5 +++++
 .../Datetime/TimestampTest.php                |   5 +++++
 ...erInputMappingOnFieldDeltaElementsTest.php |   5 +++++
 ...EntityFormFieldValidationFilteringTest.php |   5 +++++
 .../Entity/DeleteMultipleFormTest.php         |   5 +++++
 .../Drupal/FunctionalTests/FolderTest.php     |   5 +++++
 .../GetTestMethodCallerExtendsTest.php        |   7 ++++++-
 .../GetTestMethodCallerTest.php               |   7 ++++++-
 .../Hal/BaseFieldOverrideHalJsonAnonTest.php  |   5 +++++
 .../BaseFieldOverrideHalJsonBasicAuthTest.php |   5 +++++
 .../BaseFieldOverrideHalJsonCookieTest.php    |   5 +++++
 .../Hal/DateFormatHalJsonAnonTest.php         |   5 +++++
 .../Hal/DateFormatHalJsonBasicAuthTest.php    |   5 +++++
 .../Hal/DateFormatHalJsonCookieTest.php       |   5 +++++
 .../Hal/EntityFormDisplayHalJsonAnonTest.php  |   5 +++++
 .../EntityFormDisplayHalJsonBasicAuthTest.php |   5 +++++
 .../EntityFormDisplayHalJsonCookieTest.php    |   5 +++++
 .../Hal/EntityFormModeHalJsonAnonTest.php     |   5 +++++
 .../EntityFormModeHalJsonBasicAuthTest.php    |   5 +++++
 .../Hal/EntityFormModeHalJsonCookieTest.php   |   5 +++++
 .../Hal/EntityViewDisplayHalJsonAnonTest.php  |   5 +++++
 .../EntityViewDisplayHalJsonBasicAuthTest.php |   5 +++++
 .../EntityViewDisplayHalJsonCookieTest.php    |   5 +++++
 .../Hal/EntityViewModeHalJsonAnonTest.php     |   5 +++++
 .../EntityViewModeHalJsonBasicAuthTest.php    |   5 +++++
 .../Hal/EntityViewModeHalJsonCookieTest.php   |   5 +++++
 .../HttpKernel/CorsIntegrationTest.php        |   5 +++++
 .../Image/ToolkitSetupFormTest.php            |   5 +++++
 .../FunctionalTests/Image/ToolkitTest.php     |   5 +++++
 ...istributionProfileExistingSettingsTest.php |   5 +++++
 .../Installer/DistributionProfileTest.php     |   5 +++++
 ...istributionProfileTranslationQueryTest.php |   5 +++++
 .../DistributionProfileTranslationTest.php    |   5 +++++
 .../InstallProfileDependenciesBcTest.php      |   5 +++++
 .../InstallProfileDependenciesTest.php        |   5 +++++
 ...ConfigDirectorySetNoDirectoryErrorTest.php |   5 +++++
 ...allerConfigDirectorySetNoDirectoryTest.php |   5 +++++
 ...stallerCustomConfigDirectoryCreateTest.php |   5 +++++
 .../InstallerDatabaseErrorMessagesTest.php    |   5 +++++
 .../Installer/InstallerEmptySettingsTest.php  |   5 +++++
 .../InstallerExistingConfigDirectoryTest.php  |   5 +++++
 ...nstallerExistingConfigMultilingualTest.php |   5 +++++
 .../InstallerExistingConfigNoConfigTest.php   |   5 +++++
 ...nstallerExistingConfigNoSystemSiteTest.php |   5 +++++
 ...tallerExistingConfigProfileHookInstall.php |   5 +++++
 ...ingConfigSyncDirectoryMultilingualTest.php |   5 +++++
 ...gConfigSyncDirectoryProfileHookInstall.php |   5 +++++
 ...ConfigSyncDriectoryProfileMismatchTest.php |   5 +++++
 .../Installer/InstallerExistingConfigTest.php |   5 +++++
 .../InstallerExistingDatabaseSettingsTest.php |   5 +++++
 .../InstallerExistingInstallationTest.php     |   5 +++++
 ...lerExistingSettingsMismatchProfileTest.php |   5 +++++
 ...InstallerExistingSettingsNoProfileTest.php |   5 +++++
 ...ingSettingsReadOnlyMismatchProfileTest.php |   5 +++++
 .../InstallerExistingSettingsTest.php         |   5 +++++
 .../InstallerLanguageDirectionTest.php        |   5 +++++
 .../Installer/InstallerLanguagePageTest.php   |   5 +++++
 ...nEnglishProfileWithoutLocaleModuleTest.php |   5 +++++
 .../InstallerProfileRequirementsTest.php      |   5 +++++
 .../InstallerSiteConfigProfileTest.php        |   5 +++++
 .../InstallerSkipPermissionHardeningTest.php  |   5 +++++
 .../Installer/InstallerTest.php               |   5 +++++
 ...TranslationMultipleLanguageForeignTest.php |   5 +++++
 ...slationMultipleLanguageKeepEnglishTest.php |   5 +++++
 ...stallerTranslationMultipleLanguageTest.php |   5 +++++
 .../InstallerTranslationQueryTest.php         |   5 +++++
 .../Installer/InstallerTranslationTest.php    |   5 +++++
 .../Installer/MinimalInstallerTest.php        |   5 +++++
 .../MultipleDistributionsProfileTest.php      |   5 +++++
 .../Installer/SingleVisibleProfileTest.php    |   5 +++++
 .../Installer/SiteNameTest.php                |   5 +++++
 .../Installer/TestingProfileInstallTest.php   |   5 +++++
 .../FunctionalTests/MailCaptureTest.php       |   5 +++++
 .../Rest/BaseFieldOverrideJsonAnonTest.php    |   5 +++++
 .../BaseFieldOverrideJsonBasicAuthTest.php    |   5 +++++
 .../Rest/BaseFieldOverrideJsonCookieTest.php  |   5 +++++
 .../Rest/BaseFieldOverrideXmlAnonTest.php     |   5 +++++
 .../BaseFieldOverrideXmlBasicAuthTest.php     |   5 +++++
 .../Rest/BaseFieldOverrideXmlCookieTest.php   |   5 +++++
 .../Rest/DateFormatJsonAnonTest.php           |   5 +++++
 .../Rest/DateFormatJsonBasicAuthTest.php      |   5 +++++
 .../Rest/DateFormatJsonCookieTest.php         |   5 +++++
 .../Rest/DateFormatXmlAnonTest.php            |   5 +++++
 .../Rest/DateFormatXmlBasicAuthTest.php       |   5 +++++
 .../Rest/DateFormatXmlCookieTest.php          |   5 +++++
 .../Rest/EntityFormDisplayJsonAnonTest.php    |   5 +++++
 .../EntityFormDisplayJsonBasicAuthTest.php    |   5 +++++
 .../Rest/EntityFormDisplayJsonCookieTest.php  |   5 +++++
 .../Rest/EntityFormDisplayXmlAnonTest.php     |   5 +++++
 .../EntityFormDisplayXmlBasicAuthTest.php     |   5 +++++
 .../Rest/EntityFormDisplayXmlCookieTest.php   |   5 +++++
 .../Rest/EntityFormModeJsonAnonTest.php       |   5 +++++
 .../Rest/EntityFormModeJsonBasicAuthTest.php  |   5 +++++
 .../Rest/EntityFormModeJsonCookieTest.php     |   5 +++++
 .../Rest/EntityFormModeXmlAnonTest.php        |   5 +++++
 .../Rest/EntityFormModeXmlBasicAuthTest.php   |   5 +++++
 .../Rest/EntityFormModeXmlCookieTest.php      |   5 +++++
 .../Rest/EntityViewDisplayJsonAnonTest.php    |   5 +++++
 .../EntityViewDisplayJsonBasicAuthTest.php    |   5 +++++
 .../Rest/EntityViewDisplayJsonCookieTest.php  |   5 +++++
 .../Rest/EntityViewDisplayXmlAnonTest.php     |   5 +++++
 .../EntityViewDisplayXmlBasicAuthTest.php     |   5 +++++
 .../Rest/EntityViewDisplayXmlCookieTest.php   |   5 +++++
 .../Rest/EntityViewModeJsonAnonTest.php       |   5 +++++
 .../Rest/EntityViewModeJsonBasicAuthTest.php  |   5 +++++
 .../Rest/EntityViewModeJsonCookieTest.php     |   5 +++++
 .../Rest/EntityViewModeXmlAnonTest.php        |   5 +++++
 .../Rest/EntityViewModeXmlBasicAuthTest.php   |   5 +++++
 .../Rest/EntityViewModeXmlCookieTest.php      |   5 +++++
 .../Routing/CaseInsensitivePathTest.php       |   5 +++++
 .../Routing/DefaultFormatTest.php             |   5 +++++
 .../Routing/LazyRouteProviderInstallTest.php  |   5 +++++
 .../Routing/PathEncodedTest.php               |   5 +++++
 .../Routing/RouteCachingLanguageTest.php      |   5 +++++
 ...eCachingNonPathLanguageNegotiationTest.php |   5 +++++
 .../FunctionalTests/Theme/BartikTest.php      |  10 +---------
 .../FunctionalTests/Theme/ClaroTest.php       |  10 +---------
 .../FunctionalTests/Theme/ClassyTest.php      |  10 +---------
 .../FunctionalTests/UserHelpersTest.php       |   5 +++++
 .../Listeners/DeprecationListenerTrait.php    |   2 --
 1623 files changed, 8096 insertions(+), 41 deletions(-)

diff --git a/core/modules/action/tests/src/Functional/ActionListTest.php b/core/modules/action/tests/src/Functional/ActionListTest.php
index 6bb753e5e7a3..10e6637af6a8 100644
--- a/core/modules/action/tests/src/Functional/ActionListTest.php
+++ b/core/modules/action/tests/src/Functional/ActionListTest.php
@@ -18,6 +18,11 @@ class ActionListTest extends BrowserTestBase {
    */
   public static $modules = ['action'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the behavior when there are no actions to list in the admin page.
    */
diff --git a/core/modules/action/tests/src/Functional/ActionUninstallTest.php b/core/modules/action/tests/src/Functional/ActionUninstallTest.php
index 76170b166997..5e3718044e52 100644
--- a/core/modules/action/tests/src/Functional/ActionUninstallTest.php
+++ b/core/modules/action/tests/src/Functional/ActionUninstallTest.php
@@ -20,6 +20,11 @@ class ActionUninstallTest extends BrowserTestBase {
    */
   public static $modules = ['views', 'action'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests Action uninstall.
    */
diff --git a/core/modules/action/tests/src/Functional/ConfigurationTest.php b/core/modules/action/tests/src/Functional/ConfigurationTest.php
index 9b9dcf62a07f..06510ecc80aa 100644
--- a/core/modules/action/tests/src/Functional/ConfigurationTest.php
+++ b/core/modules/action/tests/src/Functional/ConfigurationTest.php
@@ -20,6 +20,12 @@ class ConfigurationTest extends BrowserTestBase {
    */
   public static $modules = ['action'];
 
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests configuration of advanced actions through administration interface.
    */
diff --git a/core/modules/action/tests/src/FunctionalJavascript/ActionFormAjaxTest.php b/core/modules/action/tests/src/FunctionalJavascript/ActionFormAjaxTest.php
index f4c85fc755d7..e32e87f67114 100644
--- a/core/modules/action/tests/src/FunctionalJavascript/ActionFormAjaxTest.php
+++ b/core/modules/action/tests/src/FunctionalJavascript/ActionFormAjaxTest.php
@@ -18,6 +18,11 @@ class ActionFormAjaxTest extends WebDriverTestBase {
    */
   protected static $modules = ['action', 'action_form_ajax_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/aggregator/tests/src/Functional/AddFeedTest.php b/core/modules/aggregator/tests/src/Functional/AddFeedTest.php
index 88a1547b7228..8809690b9ef9 100644
--- a/core/modules/aggregator/tests/src/Functional/AddFeedTest.php
+++ b/core/modules/aggregator/tests/src/Functional/AddFeedTest.php
@@ -11,6 +11,11 @@
  */
 class AddFeedTest extends AggregatorTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/aggregator/tests/src/Functional/AggregatorAdminTest.php b/core/modules/aggregator/tests/src/Functional/AggregatorAdminTest.php
index 53c1745a800f..0378cf733cf0 100644
--- a/core/modules/aggregator/tests/src/Functional/AggregatorAdminTest.php
+++ b/core/modules/aggregator/tests/src/Functional/AggregatorAdminTest.php
@@ -11,6 +11,11 @@
  */
 class AggregatorAdminTest extends AggregatorTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the settings form to ensure the correct default values are used.
    */
diff --git a/core/modules/aggregator/tests/src/Functional/AggregatorCronTest.php b/core/modules/aggregator/tests/src/Functional/AggregatorCronTest.php
index 4a3ca0b07d90..acc6b61b5fb2 100644
--- a/core/modules/aggregator/tests/src/Functional/AggregatorCronTest.php
+++ b/core/modules/aggregator/tests/src/Functional/AggregatorCronTest.php
@@ -13,6 +13,11 @@ class AggregatorCronTest extends AggregatorTestBase {
 
   use CronRunTrait;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Adds feeds and updates them via cron process.
    */
diff --git a/core/modules/aggregator/tests/src/Functional/AggregatorDisplayConfigurableTest.php b/core/modules/aggregator/tests/src/Functional/AggregatorDisplayConfigurableTest.php
index 0a2dcb652bf2..e48816c284d9 100644
--- a/core/modules/aggregator/tests/src/Functional/AggregatorDisplayConfigurableTest.php
+++ b/core/modules/aggregator/tests/src/Functional/AggregatorDisplayConfigurableTest.php
@@ -13,6 +13,11 @@
  */
 class AggregatorDisplayConfigurableTest extends AggregatorTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/aggregator/tests/src/Functional/AggregatorRenderingTest.php b/core/modules/aggregator/tests/src/Functional/AggregatorRenderingTest.php
index 1c58269af567..522ea02f3480 100644
--- a/core/modules/aggregator/tests/src/Functional/AggregatorRenderingTest.php
+++ b/core/modules/aggregator/tests/src/Functional/AggregatorRenderingTest.php
@@ -19,6 +19,11 @@ class AggregatorRenderingTest extends AggregatorTestBase {
    */
   public static $modules = ['block', 'test_page_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/aggregator/tests/src/Functional/DeleteFeedItemTest.php b/core/modules/aggregator/tests/src/Functional/DeleteFeedItemTest.php
index f70711624ace..b7cd108edd5f 100644
--- a/core/modules/aggregator/tests/src/Functional/DeleteFeedItemTest.php
+++ b/core/modules/aggregator/tests/src/Functional/DeleteFeedItemTest.php
@@ -11,6 +11,11 @@
  */
 class DeleteFeedItemTest extends AggregatorTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests running "delete items" from 'admin/config/services/aggregator' page.
    */
diff --git a/core/modules/aggregator/tests/src/Functional/DeleteFeedTest.php b/core/modules/aggregator/tests/src/Functional/DeleteFeedTest.php
index 67fe2767f097..9ff7b3435ba1 100644
--- a/core/modules/aggregator/tests/src/Functional/DeleteFeedTest.php
+++ b/core/modules/aggregator/tests/src/Functional/DeleteFeedTest.php
@@ -16,6 +16,11 @@ class DeleteFeedTest extends AggregatorTestBase {
    */
   public static $modules = ['block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Deletes a feed and ensures that all of its services are deleted.
    */
diff --git a/core/modules/aggregator/tests/src/Functional/FeedAdminDisplayTest.php b/core/modules/aggregator/tests/src/Functional/FeedAdminDisplayTest.php
index e057be6e613b..ec327a595e72 100644
--- a/core/modules/aggregator/tests/src/Functional/FeedAdminDisplayTest.php
+++ b/core/modules/aggregator/tests/src/Functional/FeedAdminDisplayTest.php
@@ -9,6 +9,11 @@
  */
 class FeedAdminDisplayTest extends AggregatorTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the "Next update" and "Last update" fields.
    */
diff --git a/core/modules/aggregator/tests/src/Functional/FeedCacheTagsTest.php b/core/modules/aggregator/tests/src/Functional/FeedCacheTagsTest.php
index 0cf6d1d03121..b1efd4609c51 100644
--- a/core/modules/aggregator/tests/src/Functional/FeedCacheTagsTest.php
+++ b/core/modules/aggregator/tests/src/Functional/FeedCacheTagsTest.php
@@ -19,6 +19,11 @@ class FeedCacheTagsTest extends EntityWithUriCacheTagsTestBase {
    */
   public static $modules = ['aggregator'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/aggregator/tests/src/Functional/FeedFetcherPluginTest.php b/core/modules/aggregator/tests/src/Functional/FeedFetcherPluginTest.php
index 1a03186c63b1..cdc2c337f9a5 100644
--- a/core/modules/aggregator/tests/src/Functional/FeedFetcherPluginTest.php
+++ b/core/modules/aggregator/tests/src/Functional/FeedFetcherPluginTest.php
@@ -11,6 +11,11 @@
  */
 class FeedFetcherPluginTest extends AggregatorTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/aggregator/tests/src/Functional/FeedLanguageTest.php b/core/modules/aggregator/tests/src/Functional/FeedLanguageTest.php
index f9fd91f9c904..aeb7b997953e 100644
--- a/core/modules/aggregator/tests/src/Functional/FeedLanguageTest.php
+++ b/core/modules/aggregator/tests/src/Functional/FeedLanguageTest.php
@@ -21,6 +21,11 @@ class FeedLanguageTest extends AggregatorTestBase {
    */
   public static $modules = ['language'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * List of langcodes.
    *
diff --git a/core/modules/aggregator/tests/src/Functional/FeedParserTest.php b/core/modules/aggregator/tests/src/Functional/FeedParserTest.php
index 71e88212cbfd..82cea3ff9e23 100644
--- a/core/modules/aggregator/tests/src/Functional/FeedParserTest.php
+++ b/core/modules/aggregator/tests/src/Functional/FeedParserTest.php
@@ -15,6 +15,11 @@
  */
 class FeedParserTest extends AggregatorTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/aggregator/tests/src/Functional/FeedProcessorPluginTest.php b/core/modules/aggregator/tests/src/Functional/FeedProcessorPluginTest.php
index 2f95f69db96b..c21f30573b70 100644
--- a/core/modules/aggregator/tests/src/Functional/FeedProcessorPluginTest.php
+++ b/core/modules/aggregator/tests/src/Functional/FeedProcessorPluginTest.php
@@ -14,6 +14,11 @@
  */
 class FeedProcessorPluginTest extends AggregatorTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/aggregator/tests/src/Functional/Hal/FeedHalJsonAnonTest.php b/core/modules/aggregator/tests/src/Functional/Hal/FeedHalJsonAnonTest.php
index 56f164b44788..834cf5dd1d7e 100644
--- a/core/modules/aggregator/tests/src/Functional/Hal/FeedHalJsonAnonTest.php
+++ b/core/modules/aggregator/tests/src/Functional/Hal/FeedHalJsonAnonTest.php
@@ -16,4 +16,9 @@ class FeedHalJsonAnonTest extends FeedHalJsonTestBase {
    */
   protected static $mimeType = 'application/hal+json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/aggregator/tests/src/Functional/Hal/FeedHalJsonBasicAuthTest.php b/core/modules/aggregator/tests/src/Functional/Hal/FeedHalJsonBasicAuthTest.php
index 58bb47351a9d..a1d36b324009 100644
--- a/core/modules/aggregator/tests/src/Functional/Hal/FeedHalJsonBasicAuthTest.php
+++ b/core/modules/aggregator/tests/src/Functional/Hal/FeedHalJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class FeedHalJsonBasicAuthTest extends FeedHalJsonTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/aggregator/tests/src/Functional/Hal/FeedHalJsonCookieTest.php b/core/modules/aggregator/tests/src/Functional/Hal/FeedHalJsonCookieTest.php
index dd574d988d36..8aa7a07c3e42 100644
--- a/core/modules/aggregator/tests/src/Functional/Hal/FeedHalJsonCookieTest.php
+++ b/core/modules/aggregator/tests/src/Functional/Hal/FeedHalJsonCookieTest.php
@@ -16,4 +16,9 @@ class FeedHalJsonCookieTest extends FeedHalJsonTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/aggregator/tests/src/Functional/Hal/ItemHalJsonAnonTest.php b/core/modules/aggregator/tests/src/Functional/Hal/ItemHalJsonAnonTest.php
index 20d37fa1ee73..629e794a9e38 100644
--- a/core/modules/aggregator/tests/src/Functional/Hal/ItemHalJsonAnonTest.php
+++ b/core/modules/aggregator/tests/src/Functional/Hal/ItemHalJsonAnonTest.php
@@ -16,6 +16,11 @@ class ItemHalJsonAnonTest extends ItemHalJsonTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/aggregator/tests/src/Functional/Hal/ItemHalJsonBasicAuthTest.php b/core/modules/aggregator/tests/src/Functional/Hal/ItemHalJsonBasicAuthTest.php
index 767c7025a476..f8792f5d753c 100644
--- a/core/modules/aggregator/tests/src/Functional/Hal/ItemHalJsonBasicAuthTest.php
+++ b/core/modules/aggregator/tests/src/Functional/Hal/ItemHalJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class ItemHalJsonBasicAuthTest extends ItemHalJsonTestBase {
    */
   public static $modules = ['hal', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/aggregator/tests/src/Functional/Hal/ItemHalJsonCookieTest.php b/core/modules/aggregator/tests/src/Functional/Hal/ItemHalJsonCookieTest.php
index 161a7357661a..d180934ab989 100644
--- a/core/modules/aggregator/tests/src/Functional/Hal/ItemHalJsonCookieTest.php
+++ b/core/modules/aggregator/tests/src/Functional/Hal/ItemHalJsonCookieTest.php
@@ -16,6 +16,11 @@ class ItemHalJsonCookieTest extends ItemHalJsonTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/aggregator/tests/src/Functional/ImportOpmlTest.php b/core/modules/aggregator/tests/src/Functional/ImportOpmlTest.php
index f9099e0eb821..89cc07eacab3 100644
--- a/core/modules/aggregator/tests/src/Functional/ImportOpmlTest.php
+++ b/core/modules/aggregator/tests/src/Functional/ImportOpmlTest.php
@@ -18,6 +18,11 @@ class ImportOpmlTest extends AggregatorTestBase {
    */
   public static $modules = ['block', 'help'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/aggregator/tests/src/Functional/ItemCacheTagsTest.php b/core/modules/aggregator/tests/src/Functional/ItemCacheTagsTest.php
index edd2ac32a92c..b86cd889e283 100644
--- a/core/modules/aggregator/tests/src/Functional/ItemCacheTagsTest.php
+++ b/core/modules/aggregator/tests/src/Functional/ItemCacheTagsTest.php
@@ -21,6 +21,11 @@ class ItemCacheTagsTest extends EntityCacheTagsTestBase {
    */
   public static $modules = ['aggregator'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/aggregator/tests/src/Functional/Rest/FeedJsonAnonTest.php b/core/modules/aggregator/tests/src/Functional/Rest/FeedJsonAnonTest.php
index 1550d74607f4..14664c18b12f 100644
--- a/core/modules/aggregator/tests/src/Functional/Rest/FeedJsonAnonTest.php
+++ b/core/modules/aggregator/tests/src/Functional/Rest/FeedJsonAnonTest.php
@@ -21,4 +21,9 @@ class FeedJsonAnonTest extends FeedResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/aggregator/tests/src/Functional/Rest/FeedJsonBasicAuthTest.php b/core/modules/aggregator/tests/src/Functional/Rest/FeedJsonBasicAuthTest.php
index e918ab9819a8..6018df892144 100644
--- a/core/modules/aggregator/tests/src/Functional/Rest/FeedJsonBasicAuthTest.php
+++ b/core/modules/aggregator/tests/src/Functional/Rest/FeedJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class FeedJsonBasicAuthTest extends FeedResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/aggregator/tests/src/Functional/Rest/FeedJsonCookieTest.php b/core/modules/aggregator/tests/src/Functional/Rest/FeedJsonCookieTest.php
index e5e0c86a4815..ef6de7bc63ac 100644
--- a/core/modules/aggregator/tests/src/Functional/Rest/FeedJsonCookieTest.php
+++ b/core/modules/aggregator/tests/src/Functional/Rest/FeedJsonCookieTest.php
@@ -26,4 +26,9 @@ class FeedJsonCookieTest extends FeedResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/aggregator/tests/src/Functional/Rest/FeedXmlAnonTest.php b/core/modules/aggregator/tests/src/Functional/Rest/FeedXmlAnonTest.php
index 41b03a6a8a98..0e2c1c5e76c6 100644
--- a/core/modules/aggregator/tests/src/Functional/Rest/FeedXmlAnonTest.php
+++ b/core/modules/aggregator/tests/src/Functional/Rest/FeedXmlAnonTest.php
@@ -23,4 +23,9 @@ class FeedXmlAnonTest extends FeedResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/aggregator/tests/src/Functional/Rest/FeedXmlBasicAuthTest.php b/core/modules/aggregator/tests/src/Functional/Rest/FeedXmlBasicAuthTest.php
index 450cc49effdc..c4bb7426d1a1 100644
--- a/core/modules/aggregator/tests/src/Functional/Rest/FeedXmlBasicAuthTest.php
+++ b/core/modules/aggregator/tests/src/Functional/Rest/FeedXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class FeedXmlBasicAuthTest extends FeedResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/aggregator/tests/src/Functional/Rest/FeedXmlCookieTest.php b/core/modules/aggregator/tests/src/Functional/Rest/FeedXmlCookieTest.php
index 3fee585d07e2..727609a5696b 100644
--- a/core/modules/aggregator/tests/src/Functional/Rest/FeedXmlCookieTest.php
+++ b/core/modules/aggregator/tests/src/Functional/Rest/FeedXmlCookieTest.php
@@ -28,4 +28,9 @@ class FeedXmlCookieTest extends FeedResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/aggregator/tests/src/Functional/Rest/ItemJsonAnonTest.php b/core/modules/aggregator/tests/src/Functional/Rest/ItemJsonAnonTest.php
index 13e24c3a4540..130a2af5cd87 100644
--- a/core/modules/aggregator/tests/src/Functional/Rest/ItemJsonAnonTest.php
+++ b/core/modules/aggregator/tests/src/Functional/Rest/ItemJsonAnonTest.php
@@ -21,4 +21,9 @@ class ItemJsonAnonTest extends ItemResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/aggregator/tests/src/Functional/Rest/ItemJsonBasicAuthTest.php b/core/modules/aggregator/tests/src/Functional/Rest/ItemJsonBasicAuthTest.php
index 15f800d1384d..383e8b59b3bc 100644
--- a/core/modules/aggregator/tests/src/Functional/Rest/ItemJsonBasicAuthTest.php
+++ b/core/modules/aggregator/tests/src/Functional/Rest/ItemJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class ItemJsonBasicAuthTest extends ItemResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/aggregator/tests/src/Functional/Rest/ItemJsonCookieTest.php b/core/modules/aggregator/tests/src/Functional/Rest/ItemJsonCookieTest.php
index 1e6567b3e9e5..587789949529 100644
--- a/core/modules/aggregator/tests/src/Functional/Rest/ItemJsonCookieTest.php
+++ b/core/modules/aggregator/tests/src/Functional/Rest/ItemJsonCookieTest.php
@@ -26,4 +26,9 @@ class ItemJsonCookieTest extends ItemResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/aggregator/tests/src/Functional/Rest/ItemXmlAnonTest.php b/core/modules/aggregator/tests/src/Functional/Rest/ItemXmlAnonTest.php
index f61a87841370..e9ce5ddc0abb 100644
--- a/core/modules/aggregator/tests/src/Functional/Rest/ItemXmlAnonTest.php
+++ b/core/modules/aggregator/tests/src/Functional/Rest/ItemXmlAnonTest.php
@@ -23,4 +23,9 @@ class ItemXmlAnonTest extends ItemResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/aggregator/tests/src/Functional/Rest/ItemXmlBasicAuthTest.php b/core/modules/aggregator/tests/src/Functional/Rest/ItemXmlBasicAuthTest.php
index 438a4233ca70..4de90303d127 100644
--- a/core/modules/aggregator/tests/src/Functional/Rest/ItemXmlBasicAuthTest.php
+++ b/core/modules/aggregator/tests/src/Functional/Rest/ItemXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class ItemXmlBasicAuthTest extends ItemResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/aggregator/tests/src/Functional/Rest/ItemXmlCookieTest.php b/core/modules/aggregator/tests/src/Functional/Rest/ItemXmlCookieTest.php
index 69144066ad43..a541956e9a30 100644
--- a/core/modules/aggregator/tests/src/Functional/Rest/ItemXmlCookieTest.php
+++ b/core/modules/aggregator/tests/src/Functional/Rest/ItemXmlCookieTest.php
@@ -28,4 +28,9 @@ class ItemXmlCookieTest extends ItemResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/aggregator/tests/src/Functional/UpdateFeedItemTest.php b/core/modules/aggregator/tests/src/Functional/UpdateFeedItemTest.php
index 2e4015e8664c..7aef9ac0f994 100644
--- a/core/modules/aggregator/tests/src/Functional/UpdateFeedItemTest.php
+++ b/core/modules/aggregator/tests/src/Functional/UpdateFeedItemTest.php
@@ -13,6 +13,11 @@
  */
 class UpdateFeedItemTest extends AggregatorTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests running "update items" from 'admin/config/services/aggregator' page.
    */
diff --git a/core/modules/aggregator/tests/src/Functional/UpdateFeedTest.php b/core/modules/aggregator/tests/src/Functional/UpdateFeedTest.php
index 62e5c4227b4e..a7ee2436cadf 100644
--- a/core/modules/aggregator/tests/src/Functional/UpdateFeedTest.php
+++ b/core/modules/aggregator/tests/src/Functional/UpdateFeedTest.php
@@ -11,6 +11,11 @@
  */
 class UpdateFeedTest extends AggregatorTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Creates a feed and attempts to update it.
    */
diff --git a/core/modules/ban/tests/src/Functional/IpAddressBlockingTest.php b/core/modules/ban/tests/src/Functional/IpAddressBlockingTest.php
index 68451dd0be94..bb77517e40b9 100644
--- a/core/modules/ban/tests/src/Functional/IpAddressBlockingTest.php
+++ b/core/modules/ban/tests/src/Functional/IpAddressBlockingTest.php
@@ -20,6 +20,11 @@ class IpAddressBlockingTest extends BrowserTestBase {
    */
   public static $modules = ['ban'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests various user input to confirm correct validation and saving of data.
    */
diff --git a/core/modules/basic_auth/tests/src/Functional/BasicAuthTest.php b/core/modules/basic_auth/tests/src/Functional/BasicAuthTest.php
index fc69ee591266..55b7fc15ead2 100644
--- a/core/modules/basic_auth/tests/src/Functional/BasicAuthTest.php
+++ b/core/modules/basic_auth/tests/src/Functional/BasicAuthTest.php
@@ -25,6 +25,11 @@ class BasicAuthTest extends BrowserTestBase {
    */
   public static $modules = ['basic_auth', 'router_test', 'locale', 'basic_auth_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test http basic authentication.
    */
diff --git a/core/modules/big_pipe/tests/src/Functional/BigPipeTest.php b/core/modules/big_pipe/tests/src/Functional/BigPipeTest.php
index 4fa7408ac2b9..a9b5eb4a441b 100644
--- a/core/modules/big_pipe/tests/src/Functional/BigPipeTest.php
+++ b/core/modules/big_pipe/tests/src/Functional/BigPipeTest.php
@@ -33,6 +33,11 @@ class BigPipeTest extends BrowserTestBase {
    */
   public static $modules = ['big_pipe', 'big_pipe_test', 'dblog'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/big_pipe/tests/src/FunctionalJavascript/BigPipeRegressionTest.php b/core/modules/big_pipe/tests/src/FunctionalJavascript/BigPipeRegressionTest.php
index 7eccf4be26f5..61fa6d950a93 100644
--- a/core/modules/big_pipe/tests/src/FunctionalJavascript/BigPipeRegressionTest.php
+++ b/core/modules/big_pipe/tests/src/FunctionalJavascript/BigPipeRegressionTest.php
@@ -34,6 +34,11 @@ class BigPipeRegressionTest extends WebDriverTestBase {
     'big_pipe_regression_test',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/block/tests/src/Functional/BlockAdminThemeTest.php b/core/modules/block/tests/src/Functional/BlockAdminThemeTest.php
index 9811b2169497..52dbc4d4c5bd 100644
--- a/core/modules/block/tests/src/Functional/BlockAdminThemeTest.php
+++ b/core/modules/block/tests/src/Functional/BlockAdminThemeTest.php
@@ -18,6 +18,11 @@ class BlockAdminThemeTest extends BrowserTestBase {
    */
   public static $modules = ['block', 'contextual'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Check for the accessibility of the admin theme on the block admin page.
    */
diff --git a/core/modules/block/tests/src/Functional/BlockCacheTest.php b/core/modules/block/tests/src/Functional/BlockCacheTest.php
index e5bb360e3e66..513fcddc0c8c 100644
--- a/core/modules/block/tests/src/Functional/BlockCacheTest.php
+++ b/core/modules/block/tests/src/Functional/BlockCacheTest.php
@@ -19,6 +19,11 @@ class BlockCacheTest extends BrowserTestBase {
    */
   public static $modules = ['block', 'block_test', 'test_page_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * A user with permission to create and edit books and to administer blocks.
    *
diff --git a/core/modules/block/tests/src/Functional/BlockDemoTest.php b/core/modules/block/tests/src/Functional/BlockDemoTest.php
index 0c8b117c61d4..313fc93c47e1 100644
--- a/core/modules/block/tests/src/Functional/BlockDemoTest.php
+++ b/core/modules/block/tests/src/Functional/BlockDemoTest.php
@@ -18,6 +18,11 @@ class BlockDemoTest extends BrowserTestBase {
    */
   public static $modules = ['block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Check for the accessibility of the admin block demo page.
    */
diff --git a/core/modules/block/tests/src/Functional/BlockFormInBlockTest.php b/core/modules/block/tests/src/Functional/BlockFormInBlockTest.php
index c0e7f589267e..6da8579ebf13 100644
--- a/core/modules/block/tests/src/Functional/BlockFormInBlockTest.php
+++ b/core/modules/block/tests/src/Functional/BlockFormInBlockTest.php
@@ -19,6 +19,11 @@ class BlockFormInBlockTest extends BrowserTestBase {
    */
   public static $modules = ['block', 'block_test', 'test_page_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/block/tests/src/Functional/BlockHiddenRegionTest.php b/core/modules/block/tests/src/Functional/BlockHiddenRegionTest.php
index fe96520eae75..a1de4739e663 100644
--- a/core/modules/block/tests/src/Functional/BlockHiddenRegionTest.php
+++ b/core/modules/block/tests/src/Functional/BlockHiddenRegionTest.php
@@ -24,6 +24,11 @@ class BlockHiddenRegionTest extends BrowserTestBase {
    */
   public static $modules = ['block', 'block_test', 'search'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/block/tests/src/Functional/BlockHookOperationTest.php b/core/modules/block/tests/src/Functional/BlockHookOperationTest.php
index 23b1f0ce5fd3..c8837da6849c 100644
--- a/core/modules/block/tests/src/Functional/BlockHookOperationTest.php
+++ b/core/modules/block/tests/src/Functional/BlockHookOperationTest.php
@@ -18,6 +18,11 @@ class BlockHookOperationTest extends BrowserTestBase {
    */
   public static $modules = ['block', 'entity_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/block/tests/src/Functional/BlockHtmlTest.php b/core/modules/block/tests/src/Functional/BlockHtmlTest.php
index 5f9afe916f7d..1d5927de81bb 100644
--- a/core/modules/block/tests/src/Functional/BlockHtmlTest.php
+++ b/core/modules/block/tests/src/Functional/BlockHtmlTest.php
@@ -18,6 +18,11 @@ class BlockHtmlTest extends BrowserTestBase {
    */
   public static $modules = ['block', 'block_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/block/tests/src/Functional/BlockInstallTest.php b/core/modules/block/tests/src/Functional/BlockInstallTest.php
index eb6c5fcebf6e..78297f9f7a4c 100644
--- a/core/modules/block/tests/src/Functional/BlockInstallTest.php
+++ b/core/modules/block/tests/src/Functional/BlockInstallTest.php
@@ -11,6 +11,11 @@
  */
 class BlockInstallTest extends BrowserTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   public function testCacheTagInvalidationUponInstallation() {
     // Warm the page cache.
     $this->drupalGet('');
diff --git a/core/modules/block/tests/src/Functional/BlockInvalidRegionTest.php b/core/modules/block/tests/src/Functional/BlockInvalidRegionTest.php
index fe8cdcb56a78..98babaf6cc50 100644
--- a/core/modules/block/tests/src/Functional/BlockInvalidRegionTest.php
+++ b/core/modules/block/tests/src/Functional/BlockInvalidRegionTest.php
@@ -20,6 +20,11 @@ class BlockInvalidRegionTest extends BrowserTestBase {
    */
   public static $modules = ['block', 'block_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   protected function setUp() {
     parent::setUp();
     // Create an admin user.
diff --git a/core/modules/block/tests/src/Functional/BlockLanguageCacheTest.php b/core/modules/block/tests/src/Functional/BlockLanguageCacheTest.php
index 9ca2b718636d..68570163ba2d 100644
--- a/core/modules/block/tests/src/Functional/BlockLanguageCacheTest.php
+++ b/core/modules/block/tests/src/Functional/BlockLanguageCacheTest.php
@@ -19,6 +19,11 @@ class BlockLanguageCacheTest extends BrowserTestBase {
    */
   public static $modules = ['block', 'language', 'menu_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * List of langcodes.
    *
diff --git a/core/modules/block/tests/src/Functional/BlockLanguageTest.php b/core/modules/block/tests/src/Functional/BlockLanguageTest.php
index 1176b052fa17..74ecba2469c5 100644
--- a/core/modules/block/tests/src/Functional/BlockLanguageTest.php
+++ b/core/modules/block/tests/src/Functional/BlockLanguageTest.php
@@ -25,6 +25,11 @@ class BlockLanguageTest extends BrowserTestBase {
    */
   public static $modules = ['language', 'block', 'content_translation'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/block/tests/src/Functional/BlockRenderOrderTest.php b/core/modules/block/tests/src/Functional/BlockRenderOrderTest.php
index ca9c2c299d0b..989e0bf3b834 100644
--- a/core/modules/block/tests/src/Functional/BlockRenderOrderTest.php
+++ b/core/modules/block/tests/src/Functional/BlockRenderOrderTest.php
@@ -19,6 +19,11 @@ class BlockRenderOrderTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     // Create a test user.
diff --git a/core/modules/block/tests/src/Functional/BlockSystemBrandingTest.php b/core/modules/block/tests/src/Functional/BlockSystemBrandingTest.php
index 89ce0c4b45a9..1c675cf9c6d6 100644
--- a/core/modules/block/tests/src/Functional/BlockSystemBrandingTest.php
+++ b/core/modules/block/tests/src/Functional/BlockSystemBrandingTest.php
@@ -16,6 +16,11 @@ class BlockSystemBrandingTest extends BlockTestBase {
    */
   public static $modules = ['block', 'system'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/block/tests/src/Functional/BlockTest.php b/core/modules/block/tests/src/Functional/BlockTest.php
index 1d653491b856..8494946a2f8f 100644
--- a/core/modules/block/tests/src/Functional/BlockTest.php
+++ b/core/modules/block/tests/src/Functional/BlockTest.php
@@ -16,6 +16,11 @@
  */
 class BlockTest extends BlockTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Tests block visibility.
    */
diff --git a/core/modules/block/tests/src/Functional/BlockUiTest.php b/core/modules/block/tests/src/Functional/BlockUiTest.php
index f7fc5d52447c..a3fc1bb180b8 100644
--- a/core/modules/block/tests/src/Functional/BlockUiTest.php
+++ b/core/modules/block/tests/src/Functional/BlockUiTest.php
@@ -21,6 +21,11 @@ class BlockUiTest extends BrowserTestBase {
    */
   public static $modules = ['block', 'block_test', 'help', 'condition_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   protected $regions;
 
   /**
diff --git a/core/modules/block/tests/src/Functional/BlockXssTest.php b/core/modules/block/tests/src/Functional/BlockXssTest.php
index 3e661d775d3d..72d38e1ee3c9 100644
--- a/core/modules/block/tests/src/Functional/BlockXssTest.php
+++ b/core/modules/block/tests/src/Functional/BlockXssTest.php
@@ -23,6 +23,11 @@ class BlockXssTest extends BrowserTestBase {
    */
   public static $modules = ['block', 'block_content', 'menu_ui', 'views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Tests that nothing is escaped other than the blocks explicitly tested.
    */
diff --git a/core/modules/block/tests/src/Functional/Hal/BlockHalJsonAnonTest.php b/core/modules/block/tests/src/Functional/Hal/BlockHalJsonAnonTest.php
index 3069667c2dc0..8e43483cd463 100644
--- a/core/modules/block/tests/src/Functional/Hal/BlockHalJsonAnonTest.php
+++ b/core/modules/block/tests/src/Functional/Hal/BlockHalJsonAnonTest.php
@@ -17,6 +17,11 @@ class BlockHalJsonAnonTest extends BlockResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/block/tests/src/Functional/Hal/BlockHalJsonBasicAuthTest.php b/core/modules/block/tests/src/Functional/Hal/BlockHalJsonBasicAuthTest.php
index f95f6d732be0..2fb4416e8432 100644
--- a/core/modules/block/tests/src/Functional/Hal/BlockHalJsonBasicAuthTest.php
+++ b/core/modules/block/tests/src/Functional/Hal/BlockHalJsonBasicAuthTest.php
@@ -17,6 +17,11 @@ class BlockHalJsonBasicAuthTest extends BlockResourceTestBase {
    */
   public static $modules = ['hal', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/block/tests/src/Functional/Hal/BlockHalJsonCookieTest.php b/core/modules/block/tests/src/Functional/Hal/BlockHalJsonCookieTest.php
index 87df9ff580bc..2b907217cfcb 100644
--- a/core/modules/block/tests/src/Functional/Hal/BlockHalJsonCookieTest.php
+++ b/core/modules/block/tests/src/Functional/Hal/BlockHalJsonCookieTest.php
@@ -17,6 +17,11 @@ class BlockHalJsonCookieTest extends BlockResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/block/tests/src/Functional/NonDefaultBlockAdminTest.php b/core/modules/block/tests/src/Functional/NonDefaultBlockAdminTest.php
index 43efccb991ce..5564a502231f 100644
--- a/core/modules/block/tests/src/Functional/NonDefaultBlockAdminTest.php
+++ b/core/modules/block/tests/src/Functional/NonDefaultBlockAdminTest.php
@@ -18,6 +18,11 @@ class NonDefaultBlockAdminTest extends BrowserTestBase {
    */
   public static $modules = ['block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/block/tests/src/Functional/Rest/BlockJsonAnonTest.php b/core/modules/block/tests/src/Functional/Rest/BlockJsonAnonTest.php
index 1d98bcc88d96..d9e3bb044d06 100644
--- a/core/modules/block/tests/src/Functional/Rest/BlockJsonAnonTest.php
+++ b/core/modules/block/tests/src/Functional/Rest/BlockJsonAnonTest.php
@@ -21,4 +21,9 @@ class BlockJsonAnonTest extends BlockResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
 }
diff --git a/core/modules/block/tests/src/Functional/Rest/BlockJsonBasicAuthTest.php b/core/modules/block/tests/src/Functional/Rest/BlockJsonBasicAuthTest.php
index 9c2a2728265c..c0deb450a5ea 100644
--- a/core/modules/block/tests/src/Functional/Rest/BlockJsonBasicAuthTest.php
+++ b/core/modules/block/tests/src/Functional/Rest/BlockJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class BlockJsonBasicAuthTest extends BlockResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/block/tests/src/Functional/Rest/BlockJsonCookieTest.php b/core/modules/block/tests/src/Functional/Rest/BlockJsonCookieTest.php
index adef298b8b6d..dc0052851485 100644
--- a/core/modules/block/tests/src/Functional/Rest/BlockJsonCookieTest.php
+++ b/core/modules/block/tests/src/Functional/Rest/BlockJsonCookieTest.php
@@ -26,4 +26,9 @@ class BlockJsonCookieTest extends BlockResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
 }
diff --git a/core/modules/block/tests/src/Functional/Rest/BlockXmlAnonTest.php b/core/modules/block/tests/src/Functional/Rest/BlockXmlAnonTest.php
index 923f02d83f25..e7bd8eb6fe6f 100644
--- a/core/modules/block/tests/src/Functional/Rest/BlockXmlAnonTest.php
+++ b/core/modules/block/tests/src/Functional/Rest/BlockXmlAnonTest.php
@@ -23,4 +23,9 @@ class BlockXmlAnonTest extends BlockResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
 }
diff --git a/core/modules/block/tests/src/Functional/Rest/BlockXmlBasicAuthTest.php b/core/modules/block/tests/src/Functional/Rest/BlockXmlBasicAuthTest.php
index 2b720d1d9fc7..0caf4c8b7544 100644
--- a/core/modules/block/tests/src/Functional/Rest/BlockXmlBasicAuthTest.php
+++ b/core/modules/block/tests/src/Functional/Rest/BlockXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class BlockXmlBasicAuthTest extends BlockResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/block/tests/src/Functional/Rest/BlockXmlCookieTest.php b/core/modules/block/tests/src/Functional/Rest/BlockXmlCookieTest.php
index 9474dbdf0d45..be8dc7229758 100644
--- a/core/modules/block/tests/src/Functional/Rest/BlockXmlCookieTest.php
+++ b/core/modules/block/tests/src/Functional/Rest/BlockXmlCookieTest.php
@@ -28,4 +28,9 @@ class BlockXmlCookieTest extends BlockResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
 }
diff --git a/core/modules/block/tests/src/Functional/Views/DisplayBlockTest.php b/core/modules/block/tests/src/Functional/Views/DisplayBlockTest.php
index 17658e462f05..77bb711b72a9 100644
--- a/core/modules/block/tests/src/Functional/Views/DisplayBlockTest.php
+++ b/core/modules/block/tests/src/Functional/Views/DisplayBlockTest.php
@@ -33,6 +33,11 @@ class DisplayBlockTest extends ViewTestBase {
    */
   public static $modules = ['node', 'block_test_views', 'test_page_test', 'contextual', 'views_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/block/tests/src/FunctionalJavascript/BlockFilterTest.php b/core/modules/block/tests/src/FunctionalJavascript/BlockFilterTest.php
index e9ecc0652606..ee9ff5fd3133 100644
--- a/core/modules/block/tests/src/FunctionalJavascript/BlockFilterTest.php
+++ b/core/modules/block/tests/src/FunctionalJavascript/BlockFilterTest.php
@@ -17,6 +17,11 @@ class BlockFilterTest extends WebDriverTestBase {
    */
   public static $modules = ['user', 'block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/block_content/tests/src/Functional/BlockContentCacheTagsTest.php b/core/modules/block_content/tests/src/Functional/BlockContentCacheTagsTest.php
index 03e0ea3daef3..c6778cab987b 100644
--- a/core/modules/block_content/tests/src/Functional/BlockContentCacheTagsTest.php
+++ b/core/modules/block_content/tests/src/Functional/BlockContentCacheTagsTest.php
@@ -22,6 +22,11 @@ class BlockContentCacheTagsTest extends EntityCacheTagsTestBase {
    */
   public static $modules = ['block_content'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/block_content/tests/src/Functional/BlockContentContextualLinksTest.php b/core/modules/block_content/tests/src/Functional/BlockContentContextualLinksTest.php
index e4e1a48ac8fd..e81078e9ccfb 100644
--- a/core/modules/block_content/tests/src/Functional/BlockContentContextualLinksTest.php
+++ b/core/modules/block_content/tests/src/Functional/BlockContentContextualLinksTest.php
@@ -16,6 +16,11 @@ class BlockContentContextualLinksTest extends BlockContentTestBase {
     'contextual',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests contextual links.
    */
diff --git a/core/modules/block_content/tests/src/Functional/BlockContentCreationTest.php b/core/modules/block_content/tests/src/Functional/BlockContentCreationTest.php
index a1b5f97a77b3..5bfd624e5ca7 100644
--- a/core/modules/block_content/tests/src/Functional/BlockContentCreationTest.php
+++ b/core/modules/block_content/tests/src/Functional/BlockContentCreationTest.php
@@ -23,6 +23,11 @@ class BlockContentCreationTest extends BlockContentTestBase {
    */
   public static $modules = ['block_content_test', 'dblog', 'field_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Permissions to grant admin user.
    *
diff --git a/core/modules/block_content/tests/src/Functional/BlockContentListTest.php b/core/modules/block_content/tests/src/Functional/BlockContentListTest.php
index 556dda69c884..ae56cda1fc13 100644
--- a/core/modules/block_content/tests/src/Functional/BlockContentListTest.php
+++ b/core/modules/block_content/tests/src/Functional/BlockContentListTest.php
@@ -22,6 +22,11 @@ class BlockContentListTest extends BlockContentTestBase {
    */
   public static $modules = ['block', 'block_content', 'config_translation'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Tests the custom block listing page.
    */
diff --git a/core/modules/block_content/tests/src/Functional/BlockContentListViewsTest.php b/core/modules/block_content/tests/src/Functional/BlockContentListViewsTest.php
index 186b32d40881..ca896c613f96 100644
--- a/core/modules/block_content/tests/src/Functional/BlockContentListViewsTest.php
+++ b/core/modules/block_content/tests/src/Functional/BlockContentListViewsTest.php
@@ -20,6 +20,11 @@ class BlockContentListViewsTest extends BlockContentTestBase {
    */
   public static $modules = ['block', 'block_content', 'config_translation', 'views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the custom block listing page.
    */
diff --git a/core/modules/block_content/tests/src/Functional/BlockContentPageViewTest.php b/core/modules/block_content/tests/src/Functional/BlockContentPageViewTest.php
index 355faf1f0f4a..c9bc68b0f3c1 100644
--- a/core/modules/block_content/tests/src/Functional/BlockContentPageViewTest.php
+++ b/core/modules/block_content/tests/src/Functional/BlockContentPageViewTest.php
@@ -16,6 +16,11 @@ class BlockContentPageViewTest extends BlockContentTestBase {
    */
   public static $modules = ['block_content_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Checks block edit and fallback functionality.
    */
diff --git a/core/modules/block_content/tests/src/Functional/BlockContentRevisionsTest.php b/core/modules/block_content/tests/src/Functional/BlockContentRevisionsTest.php
index 89708bb73aa1..743f85a38148 100644
--- a/core/modules/block_content/tests/src/Functional/BlockContentRevisionsTest.php
+++ b/core/modules/block_content/tests/src/Functional/BlockContentRevisionsTest.php
@@ -14,6 +14,11 @@
  */
 class BlockContentRevisionsTest extends BlockContentTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Stores blocks created during the test.
    * @var array
diff --git a/core/modules/block_content/tests/src/Functional/BlockContentSaveTest.php b/core/modules/block_content/tests/src/Functional/BlockContentSaveTest.php
index ce1fe96597fa..5b89d4d1b94d 100644
--- a/core/modules/block_content/tests/src/Functional/BlockContentSaveTest.php
+++ b/core/modules/block_content/tests/src/Functional/BlockContentSaveTest.php
@@ -19,6 +19,11 @@ class BlockContentSaveTest extends BlockContentTestBase {
    */
   public static $modules = ['block_content_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Sets the test up.
    */
diff --git a/core/modules/block_content/tests/src/Functional/BlockContentTranslationUITest.php b/core/modules/block_content/tests/src/Functional/BlockContentTranslationUITest.php
index fc11d782c991..09d0fd95acb6 100644
--- a/core/modules/block_content/tests/src/Functional/BlockContentTranslationUITest.php
+++ b/core/modules/block_content/tests/src/Functional/BlockContentTranslationUITest.php
@@ -27,6 +27,11 @@ class BlockContentTranslationUITest extends ContentTranslationUITestBase {
     'block_content',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/block_content/tests/src/Functional/BlockContentTypeTest.php b/core/modules/block_content/tests/src/Functional/BlockContentTypeTest.php
index 452bea07863e..2e172551318e 100644
--- a/core/modules/block_content/tests/src/Functional/BlockContentTypeTest.php
+++ b/core/modules/block_content/tests/src/Functional/BlockContentTypeTest.php
@@ -23,6 +23,11 @@ class BlockContentTypeTest extends BlockContentTestBase {
    */
   public static $modules = ['field_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Permissions to grant admin user.
    *
diff --git a/core/modules/block_content/tests/src/Functional/BlockContentValidationTest.php b/core/modules/block_content/tests/src/Functional/BlockContentValidationTest.php
index 7baaffd4074f..293234ba5235 100644
--- a/core/modules/block_content/tests/src/Functional/BlockContentValidationTest.php
+++ b/core/modules/block_content/tests/src/Functional/BlockContentValidationTest.php
@@ -11,6 +11,11 @@
  */
 class BlockContentValidationTest extends BlockContentTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the block content validation constraints.
    */
diff --git a/core/modules/block_content/tests/src/Functional/Hal/BlockContentHalJsonAnonTest.php b/core/modules/block_content/tests/src/Functional/Hal/BlockContentHalJsonAnonTest.php
index 33c1108d2486..6f7a1b6147c9 100644
--- a/core/modules/block_content/tests/src/Functional/Hal/BlockContentHalJsonAnonTest.php
+++ b/core/modules/block_content/tests/src/Functional/Hal/BlockContentHalJsonAnonTest.php
@@ -20,6 +20,11 @@ class BlockContentHalJsonAnonTest extends BlockContentResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/block_content/tests/src/Functional/Hal/BlockContentHalJsonBasicAuthTest.php b/core/modules/block_content/tests/src/Functional/Hal/BlockContentHalJsonBasicAuthTest.php
index b9b262e9bedc..074eadd81fc9 100644
--- a/core/modules/block_content/tests/src/Functional/Hal/BlockContentHalJsonBasicAuthTest.php
+++ b/core/modules/block_content/tests/src/Functional/Hal/BlockContentHalJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class BlockContentHalJsonBasicAuthTest extends BlockContentHalJsonAnonTest {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/block_content/tests/src/Functional/Hal/BlockContentHalJsonCookieTest.php b/core/modules/block_content/tests/src/Functional/Hal/BlockContentHalJsonCookieTest.php
index 2446dfb657bc..a751dae70c2b 100644
--- a/core/modules/block_content/tests/src/Functional/Hal/BlockContentHalJsonCookieTest.php
+++ b/core/modules/block_content/tests/src/Functional/Hal/BlockContentHalJsonCookieTest.php
@@ -16,4 +16,9 @@ class BlockContentHalJsonCookieTest extends BlockContentHalJsonAnonTest {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/block_content/tests/src/Functional/Hal/BlockContentTypeHalJsonAnonTest.php b/core/modules/block_content/tests/src/Functional/Hal/BlockContentTypeHalJsonAnonTest.php
index 3bfff1068a81..1a7d4e7056d6 100644
--- a/core/modules/block_content/tests/src/Functional/Hal/BlockContentTypeHalJsonAnonTest.php
+++ b/core/modules/block_content/tests/src/Functional/Hal/BlockContentTypeHalJsonAnonTest.php
@@ -17,6 +17,11 @@ class BlockContentTypeHalJsonAnonTest extends BlockContentTypeResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/block_content/tests/src/Functional/Hal/BlockContentTypeHalJsonBasicAuthTest.php b/core/modules/block_content/tests/src/Functional/Hal/BlockContentTypeHalJsonBasicAuthTest.php
index 6112c2b60a71..41eeb87328ed 100644
--- a/core/modules/block_content/tests/src/Functional/Hal/BlockContentTypeHalJsonBasicAuthTest.php
+++ b/core/modules/block_content/tests/src/Functional/Hal/BlockContentTypeHalJsonBasicAuthTest.php
@@ -17,6 +17,11 @@ class BlockContentTypeHalJsonBasicAuthTest extends BlockContentTypeResourceTestB
    */
   public static $modules = ['hal', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/block_content/tests/src/Functional/Hal/BlockContentTypeHalJsonCookieTest.php b/core/modules/block_content/tests/src/Functional/Hal/BlockContentTypeHalJsonCookieTest.php
index 889d775cde40..006d08bfbae9 100644
--- a/core/modules/block_content/tests/src/Functional/Hal/BlockContentTypeHalJsonCookieTest.php
+++ b/core/modules/block_content/tests/src/Functional/Hal/BlockContentTypeHalJsonCookieTest.php
@@ -17,6 +17,11 @@ class BlockContentTypeHalJsonCookieTest extends BlockContentTypeResourceTestBase
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/block_content/tests/src/Functional/PageEditTest.php b/core/modules/block_content/tests/src/Functional/PageEditTest.php
index 3edd7108e914..1cc8c1946cae 100644
--- a/core/modules/block_content/tests/src/Functional/PageEditTest.php
+++ b/core/modules/block_content/tests/src/Functional/PageEditTest.php
@@ -12,6 +12,11 @@
  */
 class PageEditTest extends BlockContentTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/block_content/tests/src/Functional/Rest/BlockContentJsonAnonTest.php b/core/modules/block_content/tests/src/Functional/Rest/BlockContentJsonAnonTest.php
index 844f9278b589..31a60f1f591d 100644
--- a/core/modules/block_content/tests/src/Functional/Rest/BlockContentJsonAnonTest.php
+++ b/core/modules/block_content/tests/src/Functional/Rest/BlockContentJsonAnonTest.php
@@ -21,4 +21,9 @@ class BlockContentJsonAnonTest extends BlockContentResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/block_content/tests/src/Functional/Rest/BlockContentJsonBasicAuthTest.php b/core/modules/block_content/tests/src/Functional/Rest/BlockContentJsonBasicAuthTest.php
index 63bf314eb511..f87ce906d76d 100644
--- a/core/modules/block_content/tests/src/Functional/Rest/BlockContentJsonBasicAuthTest.php
+++ b/core/modules/block_content/tests/src/Functional/Rest/BlockContentJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class BlockContentJsonBasicAuthTest extends BlockContentResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/block_content/tests/src/Functional/Rest/BlockContentJsonCookieTest.php b/core/modules/block_content/tests/src/Functional/Rest/BlockContentJsonCookieTest.php
index 4c2773407233..c4eaf0742f78 100644
--- a/core/modules/block_content/tests/src/Functional/Rest/BlockContentJsonCookieTest.php
+++ b/core/modules/block_content/tests/src/Functional/Rest/BlockContentJsonCookieTest.php
@@ -26,4 +26,9 @@ class BlockContentJsonCookieTest extends BlockContentResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/block_content/tests/src/Functional/Rest/BlockContentTypeJsonAnonTest.php b/core/modules/block_content/tests/src/Functional/Rest/BlockContentTypeJsonAnonTest.php
index 3fcbd43f53e1..244e43889acd 100644
--- a/core/modules/block_content/tests/src/Functional/Rest/BlockContentTypeJsonAnonTest.php
+++ b/core/modules/block_content/tests/src/Functional/Rest/BlockContentTypeJsonAnonTest.php
@@ -21,4 +21,9 @@ class BlockContentTypeJsonAnonTest extends BlockContentTypeResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/block_content/tests/src/Functional/Rest/BlockContentTypeJsonBasicAuthTest.php b/core/modules/block_content/tests/src/Functional/Rest/BlockContentTypeJsonBasicAuthTest.php
index a993d1f1bd5a..709dcfd5d47b 100644
--- a/core/modules/block_content/tests/src/Functional/Rest/BlockContentTypeJsonBasicAuthTest.php
+++ b/core/modules/block_content/tests/src/Functional/Rest/BlockContentTypeJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class BlockContentTypeJsonBasicAuthTest extends BlockContentTypeResourceTestBase
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/block_content/tests/src/Functional/Rest/BlockContentTypeJsonCookieTest.php b/core/modules/block_content/tests/src/Functional/Rest/BlockContentTypeJsonCookieTest.php
index c938f1393d71..7746171cd44e 100644
--- a/core/modules/block_content/tests/src/Functional/Rest/BlockContentTypeJsonCookieTest.php
+++ b/core/modules/block_content/tests/src/Functional/Rest/BlockContentTypeJsonCookieTest.php
@@ -26,4 +26,9 @@ class BlockContentTypeJsonCookieTest extends BlockContentTypeResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/block_content/tests/src/Functional/Rest/BlockContentTypeXmlAnonTest.php b/core/modules/block_content/tests/src/Functional/Rest/BlockContentTypeXmlAnonTest.php
index 2277d6b9788f..cade87714a01 100644
--- a/core/modules/block_content/tests/src/Functional/Rest/BlockContentTypeXmlAnonTest.php
+++ b/core/modules/block_content/tests/src/Functional/Rest/BlockContentTypeXmlAnonTest.php
@@ -23,4 +23,9 @@ class BlockContentTypeXmlAnonTest extends BlockContentTypeResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/block_content/tests/src/Functional/Rest/BlockContentTypeXmlBasicAuthTest.php b/core/modules/block_content/tests/src/Functional/Rest/BlockContentTypeXmlBasicAuthTest.php
index a878c7d5b3cd..17b834700d6e 100644
--- a/core/modules/block_content/tests/src/Functional/Rest/BlockContentTypeXmlBasicAuthTest.php
+++ b/core/modules/block_content/tests/src/Functional/Rest/BlockContentTypeXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class BlockContentTypeXmlBasicAuthTest extends BlockContentTypeResourceTestBase
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/block_content/tests/src/Functional/Rest/BlockContentTypeXmlCookieTest.php b/core/modules/block_content/tests/src/Functional/Rest/BlockContentTypeXmlCookieTest.php
index 836c330dcea3..bee3ed83d4d5 100644
--- a/core/modules/block_content/tests/src/Functional/Rest/BlockContentTypeXmlCookieTest.php
+++ b/core/modules/block_content/tests/src/Functional/Rest/BlockContentTypeXmlCookieTest.php
@@ -28,4 +28,9 @@ class BlockContentTypeXmlCookieTest extends BlockContentTypeResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/block_content/tests/src/Functional/Rest/BlockContentXmlAnonTest.php b/core/modules/block_content/tests/src/Functional/Rest/BlockContentXmlAnonTest.php
index fba08ed473fc..d32cb121786b 100644
--- a/core/modules/block_content/tests/src/Functional/Rest/BlockContentXmlAnonTest.php
+++ b/core/modules/block_content/tests/src/Functional/Rest/BlockContentXmlAnonTest.php
@@ -23,4 +23,9 @@ class BlockContentXmlAnonTest extends BlockContentResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/block_content/tests/src/Functional/Rest/BlockContentXmlBasicAuthTest.php b/core/modules/block_content/tests/src/Functional/Rest/BlockContentXmlBasicAuthTest.php
index 199abea08dce..9b593c9049fd 100644
--- a/core/modules/block_content/tests/src/Functional/Rest/BlockContentXmlBasicAuthTest.php
+++ b/core/modules/block_content/tests/src/Functional/Rest/BlockContentXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class BlockContentXmlBasicAuthTest extends BlockContentResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/block_content/tests/src/Functional/Rest/BlockContentXmlCookieTest.php b/core/modules/block_content/tests/src/Functional/Rest/BlockContentXmlCookieTest.php
index 62514559528f..ff39556b1163 100644
--- a/core/modules/block_content/tests/src/Functional/Rest/BlockContentXmlCookieTest.php
+++ b/core/modules/block_content/tests/src/Functional/Rest/BlockContentXmlCookieTest.php
@@ -28,4 +28,9 @@ class BlockContentXmlCookieTest extends BlockContentResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/block_content/tests/src/Functional/UnpublishedBlockTest.php b/core/modules/block_content/tests/src/Functional/UnpublishedBlockTest.php
index 8dbecedf14b7..62e41dd32731 100644
--- a/core/modules/block_content/tests/src/Functional/UnpublishedBlockTest.php
+++ b/core/modules/block_content/tests/src/Functional/UnpublishedBlockTest.php
@@ -20,6 +20,11 @@ class UnpublishedBlockTest extends BrowserTestBase {
    */
   public static $modules = ['block_content'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Tests unpublishing of block_content entities.
    */
diff --git a/core/modules/block_content/tests/src/Functional/Views/BlockContentFieldFilterTest.php b/core/modules/block_content/tests/src/Functional/Views/BlockContentFieldFilterTest.php
index a77c2e1b297c..2a612839af6a 100644
--- a/core/modules/block_content/tests/src/Functional/Views/BlockContentFieldFilterTest.php
+++ b/core/modules/block_content/tests/src/Functional/Views/BlockContentFieldFilterTest.php
@@ -17,6 +17,11 @@ class BlockContentFieldFilterTest extends BlockContentTestBase {
    */
   public static $modules = ['language'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/block_content/tests/src/Functional/Views/BlockContentIntegrationTest.php b/core/modules/block_content/tests/src/Functional/Views/BlockContentIntegrationTest.php
index 93661578bd9d..8f9e03d25713 100644
--- a/core/modules/block_content/tests/src/Functional/Views/BlockContentIntegrationTest.php
+++ b/core/modules/block_content/tests/src/Functional/Views/BlockContentIntegrationTest.php
@@ -9,6 +9,11 @@
  */
 class BlockContentIntegrationTest extends BlockContentTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/block_content/tests/src/Functional/Views/BlockContentRedirectTest.php b/core/modules/block_content/tests/src/Functional/Views/BlockContentRedirectTest.php
index 10ce140e967e..81b206cccf31 100644
--- a/core/modules/block_content/tests/src/Functional/Views/BlockContentRedirectTest.php
+++ b/core/modules/block_content/tests/src/Functional/Views/BlockContentRedirectTest.php
@@ -23,6 +23,11 @@ class BlockContentRedirectTest extends BlockContentTestBase {
    */
   public static $modules = ['block', 'block_content', 'views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the redirect destination when editing block content.
    */
diff --git a/core/modules/block_content/tests/src/Functional/Views/BlockContentWizardTest.php b/core/modules/block_content/tests/src/Functional/Views/BlockContentWizardTest.php
index 2c59e5c50fe8..d0c997e216c1 100644
--- a/core/modules/block_content/tests/src/Functional/Views/BlockContentWizardTest.php
+++ b/core/modules/block_content/tests/src/Functional/Views/BlockContentWizardTest.php
@@ -16,6 +16,11 @@ class BlockContentWizardTest extends BlockContentTestBase {
    */
   public static $modules = ['block_content', 'views_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/block_content/tests/src/Functional/Views/FieldTypeTest.php b/core/modules/block_content/tests/src/Functional/Views/FieldTypeTest.php
index 8ff2fc05ca0e..87a595c5831d 100644
--- a/core/modules/block_content/tests/src/Functional/Views/FieldTypeTest.php
+++ b/core/modules/block_content/tests/src/Functional/Views/FieldTypeTest.php
@@ -11,6 +11,11 @@
  */
 class FieldTypeTest extends BlockContentTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/block_place/tests/src/Functional/BlockPlaceTest.php b/core/modules/block_place/tests/src/Functional/BlockPlaceTest.php
index 9666ec1d15d0..8eb78254c846 100644
--- a/core/modules/block_place/tests/src/Functional/BlockPlaceTest.php
+++ b/core/modules/block_place/tests/src/Functional/BlockPlaceTest.php
@@ -20,6 +20,11 @@ class BlockPlaceTest extends BrowserTestBase {
    */
   public static $modules = ['block', 'block_place', 'toolbar'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests placing blocks as an admin.
    */
diff --git a/core/modules/book/tests/src/Functional/BookBreadcrumbTest.php b/core/modules/book/tests/src/Functional/BookBreadcrumbTest.php
index 5271c8e7b87d..e539867a233b 100644
--- a/core/modules/book/tests/src/Functional/BookBreadcrumbTest.php
+++ b/core/modules/book/tests/src/Functional/BookBreadcrumbTest.php
@@ -18,6 +18,11 @@ class BookBreadcrumbTest extends BrowserTestBase {
    */
   public static $modules = ['book', 'block', 'book_breadcrumb_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * A book node.
    *
diff --git a/core/modules/book/tests/src/Functional/BookContentModerationTest.php b/core/modules/book/tests/src/Functional/BookContentModerationTest.php
index b9c7cd284184..00c234dafa10 100644
--- a/core/modules/book/tests/src/Functional/BookContentModerationTest.php
+++ b/core/modules/book/tests/src/Functional/BookContentModerationTest.php
@@ -22,6 +22,11 @@ class BookContentModerationTest extends BrowserTestBase {
    */
   public static $modules = ['book', 'block', 'book_test', 'content_moderation'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/book/tests/src/Functional/BookTest.php b/core/modules/book/tests/src/Functional/BookTest.php
index 0361d49a61e9..e1e81955d23f 100644
--- a/core/modules/book/tests/src/Functional/BookTest.php
+++ b/core/modules/book/tests/src/Functional/BookTest.php
@@ -23,6 +23,11 @@ class BookTest extends BrowserTestBase {
    */
   public static $modules = ['book', 'block', 'node_access_test', 'book_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * A user with permission to view a book and access printer-friendly version.
    *
diff --git a/core/modules/book/tests/src/Functional/Views/BookRelationshipTest.php b/core/modules/book/tests/src/Functional/Views/BookRelationshipTest.php
index 30b8a8445a12..b8e7fa04fee2 100644
--- a/core/modules/book/tests/src/Functional/Views/BookRelationshipTest.php
+++ b/core/modules/book/tests/src/Functional/Views/BookRelationshipTest.php
@@ -28,6 +28,11 @@ class BookRelationshipTest extends ViewTestBase {
    */
   public static $modules = ['book_test_views', 'book', 'views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A book node.
    *
diff --git a/core/modules/book/tests/src/FunctionalJavascript/BookJavascriptTest.php b/core/modules/book/tests/src/FunctionalJavascript/BookJavascriptTest.php
index dc9b8125cccc..7f42954a4e4b 100644
--- a/core/modules/book/tests/src/FunctionalJavascript/BookJavascriptTest.php
+++ b/core/modules/book/tests/src/FunctionalJavascript/BookJavascriptTest.php
@@ -19,6 +19,11 @@ class BookJavascriptTest extends WebDriverTestBase {
    */
   public static $modules = ['book'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests re-ordering of books.
    */
diff --git a/core/modules/ckeditor/tests/src/Functional/CKEditorAdminTest.php b/core/modules/ckeditor/tests/src/Functional/CKEditorAdminTest.php
index aeba60fd7545..87c358cd684f 100644
--- a/core/modules/ckeditor/tests/src/Functional/CKEditorAdminTest.php
+++ b/core/modules/ckeditor/tests/src/Functional/CKEditorAdminTest.php
@@ -22,6 +22,11 @@ class CKEditorAdminTest extends BrowserTestBase {
    */
   public static $modules = ['filter', 'editor', 'ckeditor'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with the 'administer filters' permission.
    *
diff --git a/core/modules/ckeditor/tests/src/Functional/CKEditorLoadingTest.php b/core/modules/ckeditor/tests/src/Functional/CKEditorLoadingTest.php
index d56919636c6d..71908383480d 100644
--- a/core/modules/ckeditor/tests/src/Functional/CKEditorLoadingTest.php
+++ b/core/modules/ckeditor/tests/src/Functional/CKEditorLoadingTest.php
@@ -20,6 +20,11 @@ class CKEditorLoadingTest extends BrowserTestBase {
    */
   public static $modules = ['filter', 'editor', 'ckeditor', 'node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * An untrusted user with access to only the 'plain_text' format.
    *
diff --git a/core/modules/ckeditor/tests/src/Functional/CKEditorStylesComboAdminTest.php b/core/modules/ckeditor/tests/src/Functional/CKEditorStylesComboAdminTest.php
index 9f41834de5ba..d3ec916ce66c 100644
--- a/core/modules/ckeditor/tests/src/Functional/CKEditorStylesComboAdminTest.php
+++ b/core/modules/ckeditor/tests/src/Functional/CKEditorStylesComboAdminTest.php
@@ -20,6 +20,11 @@ class CKEditorStylesComboAdminTest extends BrowserTestBase {
    */
   public static $modules = ['filter', 'editor', 'ckeditor'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with the 'administer filters' permission.
    *
diff --git a/core/modules/ckeditor/tests/src/Functional/CKEditorToolbarButtonTest.php b/core/modules/ckeditor/tests/src/Functional/CKEditorToolbarButtonTest.php
index c47b67b0b496..821beee47da8 100644
--- a/core/modules/ckeditor/tests/src/Functional/CKEditorToolbarButtonTest.php
+++ b/core/modules/ckeditor/tests/src/Functional/CKEditorToolbarButtonTest.php
@@ -21,6 +21,11 @@ class CKEditorToolbarButtonTest extends BrowserTestBase {
    */
   public static $modules = ['filter', 'editor', 'ckeditor', 'locale'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/ckeditor/tests/src/FunctionalJavascript/AjaxCssTest.php b/core/modules/ckeditor/tests/src/FunctionalJavascript/AjaxCssTest.php
index ddb53d8303e8..5dfa7ea45761 100644
--- a/core/modules/ckeditor/tests/src/FunctionalJavascript/AjaxCssTest.php
+++ b/core/modules/ckeditor/tests/src/FunctionalJavascript/AjaxCssTest.php
@@ -18,6 +18,11 @@ class AjaxCssTest extends WebDriverTestBase {
    */
   public static $modules = ['ckeditor', 'ckeditor_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/ckeditor/tests/src/FunctionalJavascript/CKEditorIntegrationTest.php b/core/modules/ckeditor/tests/src/FunctionalJavascript/CKEditorIntegrationTest.php
index 82da82519a4e..2a66b65ca27c 100644
--- a/core/modules/ckeditor/tests/src/FunctionalJavascript/CKEditorIntegrationTest.php
+++ b/core/modules/ckeditor/tests/src/FunctionalJavascript/CKEditorIntegrationTest.php
@@ -20,6 +20,11 @@ class CKEditorIntegrationTest extends WebDriverTestBase {
 
   use CKEditorTestTrait;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The account.
    *
diff --git a/core/modules/color/tests/src/Functional/ColorConfigSchemaTest.php b/core/modules/color/tests/src/Functional/ColorConfigSchemaTest.php
index 2fa95d1478d2..001c98c8fa17 100644
--- a/core/modules/color/tests/src/Functional/ColorConfigSchemaTest.php
+++ b/core/modules/color/tests/src/Functional/ColorConfigSchemaTest.php
@@ -18,6 +18,11 @@ class ColorConfigSchemaTest extends BrowserTestBase {
    */
   public static $modules = ['color'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with administrative permissions.
    *
diff --git a/core/modules/color/tests/src/Functional/ColorSafePreviewTest.php b/core/modules/color/tests/src/Functional/ColorSafePreviewTest.php
index fa4e81ecf2df..34d0d70d1596 100644
--- a/core/modules/color/tests/src/Functional/ColorSafePreviewTest.php
+++ b/core/modules/color/tests/src/Functional/ColorSafePreviewTest.php
@@ -19,6 +19,11 @@ class ColorSafePreviewTest extends BrowserTestBase {
    */
   public static $modules = ['color', 'color_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with administrative permissions.
    *
diff --git a/core/modules/color/tests/src/Functional/ColorTest.php b/core/modules/color/tests/src/Functional/ColorTest.php
index 5e1bf96eccc5..caaa2c9fee9b 100644
--- a/core/modules/color/tests/src/Functional/ColorTest.php
+++ b/core/modules/color/tests/src/Functional/ColorTest.php
@@ -19,6 +19,11 @@ class ColorTest extends BrowserTestBase {
    */
   public static $modules = ['color', 'color_test', 'block', 'file'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with administrative permissions.
    *
diff --git a/core/modules/comment/tests/src/Functional/CommentAccessTest.php b/core/modules/comment/tests/src/Functional/CommentAccessTest.php
index b2e4725785ae..a92fd5e7924d 100644
--- a/core/modules/comment/tests/src/Functional/CommentAccessTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentAccessTest.php
@@ -24,6 +24,11 @@ class CommentAccessTest extends BrowserTestBase {
     'comment',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Node for commenting.
    *
diff --git a/core/modules/comment/tests/src/Functional/CommentActionsTest.php b/core/modules/comment/tests/src/Functional/CommentActionsTest.php
index 326749b7c03c..21e1e2dfa656 100644
--- a/core/modules/comment/tests/src/Functional/CommentActionsTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentActionsTest.php
@@ -19,6 +19,11 @@ class CommentActionsTest extends CommentTestBase {
    */
   public static $modules = ['dblog', 'action'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests comment publish and unpublish actions.
    */
diff --git a/core/modules/comment/tests/src/Functional/CommentAdminTest.php b/core/modules/comment/tests/src/Functional/CommentAdminTest.php
index 2c8cb172e37d..47a3c6494a58 100644
--- a/core/modules/comment/tests/src/Functional/CommentAdminTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentAdminTest.php
@@ -15,6 +15,11 @@
  */
 class CommentAdminTest extends CommentTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/comment/tests/src/Functional/CommentAnonymousTest.php b/core/modules/comment/tests/src/Functional/CommentAnonymousTest.php
index 82108496ce9c..c18053183430 100644
--- a/core/modules/comment/tests/src/Functional/CommentAnonymousTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentAnonymousTest.php
@@ -12,6 +12,11 @@
  */
 class CommentAnonymousTest extends CommentTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/comment/tests/src/Functional/CommentBlockTest.php b/core/modules/comment/tests/src/Functional/CommentBlockTest.php
index b3ee6b8cfb58..954728bf712e 100644
--- a/core/modules/comment/tests/src/Functional/CommentBlockTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentBlockTest.php
@@ -19,6 +19,11 @@ class CommentBlockTest extends CommentTestBase {
    */
   public static $modules = ['block', 'views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     // Update admin user to have the 'administer blocks' permission.
diff --git a/core/modules/comment/tests/src/Functional/CommentBookTest.php b/core/modules/comment/tests/src/Functional/CommentBookTest.php
index 45693b57fbd0..b461f7098abe 100644
--- a/core/modules/comment/tests/src/Functional/CommentBookTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentBookTest.php
@@ -24,6 +24,11 @@ class CommentBookTest extends BrowserTestBase {
    */
   public static $modules = ['book', 'comment'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/comment/tests/src/Functional/CommentCSSTest.php b/core/modules/comment/tests/src/Functional/CommentCSSTest.php
index c281f63ce38c..54db7a1636d7 100644
--- a/core/modules/comment/tests/src/Functional/CommentCSSTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentCSSTest.php
@@ -17,6 +17,11 @@ class CommentCSSTest extends CommentTestBase {
 
   use GeneratePermutationsTrait;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/comment/tests/src/Functional/CommentCacheTagsTest.php b/core/modules/comment/tests/src/Functional/CommentCacheTagsTest.php
index 9db678f31a35..43b698689ea9 100644
--- a/core/modules/comment/tests/src/Functional/CommentCacheTagsTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentCacheTagsTest.php
@@ -27,6 +27,11 @@ class CommentCacheTagsTest extends EntityWithUriCacheTagsTestBase {
    */
   public static $modules = ['comment'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * @var \Drupal\entity_test\Entity\EntityTest
    */
diff --git a/core/modules/comment/tests/src/Functional/CommentEntityTest.php b/core/modules/comment/tests/src/Functional/CommentEntityTest.php
index 9f8eb8c1e225..79ab591a4a71 100644
--- a/core/modules/comment/tests/src/Functional/CommentEntityTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentEntityTest.php
@@ -25,6 +25,11 @@ class CommentEntityTest extends CommentTestBase {
    */
   public static $modules = ['block', 'comment', 'node', 'history', 'field_ui', 'datetime', 'taxonomy'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected $vocab;
   protected $commentType;
 
diff --git a/core/modules/comment/tests/src/Functional/CommentFieldsTest.php b/core/modules/comment/tests/src/Functional/CommentFieldsTest.php
index 23ec524f3303..522303916795 100644
--- a/core/modules/comment/tests/src/Functional/CommentFieldsTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentFieldsTest.php
@@ -22,6 +22,11 @@ class CommentFieldsTest extends CommentTestBase {
    */
   public static $modules = ['field_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Tests that the default 'comment_body' field is correctly added.
    */
diff --git a/core/modules/comment/tests/src/Functional/CommentInterfaceTest.php b/core/modules/comment/tests/src/Functional/CommentInterfaceTest.php
index b84ff3dbdbc9..9514664b6690 100644
--- a/core/modules/comment/tests/src/Functional/CommentInterfaceTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentInterfaceTest.php
@@ -18,6 +18,11 @@
  */
 class CommentInterfaceTest extends CommentTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Set up comments to have subject and preview disabled.
    */
diff --git a/core/modules/comment/tests/src/Functional/CommentLanguageTest.php b/core/modules/comment/tests/src/Functional/CommentLanguageTest.php
index f8c21fc843e4..000ecd28c8c8 100644
--- a/core/modules/comment/tests/src/Functional/CommentLanguageTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentLanguageTest.php
@@ -29,6 +29,11 @@ class CommentLanguageTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'language', 'language_test', 'comment_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/comment/tests/src/Functional/CommentLinksAlterTest.php b/core/modules/comment/tests/src/Functional/CommentLinksAlterTest.php
index e49361b651b8..7c4349b1bdc5 100644
--- a/core/modules/comment/tests/src/Functional/CommentLinksAlterTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentLinksAlterTest.php
@@ -11,6 +11,11 @@ class CommentLinksAlterTest extends CommentTestBase {
 
   public static $modules = ['comment_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/comment/tests/src/Functional/CommentLinksTest.php b/core/modules/comment/tests/src/Functional/CommentLinksTest.php
index 0b9c4181a19b..34a815c0287b 100644
--- a/core/modules/comment/tests/src/Functional/CommentLinksTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentLinksTest.php
@@ -38,6 +38,11 @@ class CommentLinksTest extends CommentTestBase {
    */
   public static $modules = ['views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that comment links are output and can be hidden.
    */
diff --git a/core/modules/comment/tests/src/Functional/CommentNewIndicatorTest.php b/core/modules/comment/tests/src/Functional/CommentNewIndicatorTest.php
index b7426ecdad4c..99219f1fccaf 100644
--- a/core/modules/comment/tests/src/Functional/CommentNewIndicatorTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentNewIndicatorTest.php
@@ -24,6 +24,11 @@ class CommentNewIndicatorTest extends CommentTestBase {
    */
   public static $modules = ['views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Get node "x new comments" metadata from the server for the current user.
    *
diff --git a/core/modules/comment/tests/src/Functional/CommentNodeAccessTest.php b/core/modules/comment/tests/src/Functional/CommentNodeAccessTest.php
index 6842dc137fe6..4b21c492cd29 100644
--- a/core/modules/comment/tests/src/Functional/CommentNodeAccessTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentNodeAccessTest.php
@@ -21,6 +21,11 @@ class CommentNodeAccessTest extends CommentTestBase {
    */
   public static $modules = ['node_access_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/comment/tests/src/Functional/CommentNodeChangesTest.php b/core/modules/comment/tests/src/Functional/CommentNodeChangesTest.php
index 8229aefd5f5b..0b9fddfd3dca 100644
--- a/core/modules/comment/tests/src/Functional/CommentNodeChangesTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentNodeChangesTest.php
@@ -13,6 +13,11 @@
  */
 class CommentNodeChangesTest extends CommentTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that comments are deleted with the node.
    */
diff --git a/core/modules/comment/tests/src/Functional/CommentNonNodeTest.php b/core/modules/comment/tests/src/Functional/CommentNonNodeTest.php
index ceae6f33668d..a543510062fa 100644
--- a/core/modules/comment/tests/src/Functional/CommentNonNodeTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentNonNodeTest.php
@@ -28,6 +28,11 @@ class CommentNonNodeTest extends BrowserTestBase {
 
   public static $modules = ['comment', 'user', 'field_ui', 'entity_test', 'block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * An administrative user with permission to configure comment settings.
    *
diff --git a/core/modules/comment/tests/src/Functional/CommentPagerTest.php b/core/modules/comment/tests/src/Functional/CommentPagerTest.php
index 56adbf7a81dc..25da658ad650 100644
--- a/core/modules/comment/tests/src/Functional/CommentPagerTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentPagerTest.php
@@ -13,6 +13,11 @@
  */
 class CommentPagerTest extends CommentTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Confirms comment paging works correctly with flat and threaded comments.
    */
diff --git a/core/modules/comment/tests/src/Functional/CommentRssTest.php b/core/modules/comment/tests/src/Functional/CommentRssTest.php
index 33122dd2cd72..0ae74e92d27a 100644
--- a/core/modules/comment/tests/src/Functional/CommentRssTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentRssTest.php
@@ -23,6 +23,11 @@ class CommentRssTest extends CommentTestBase {
    */
   public static $modules = ['views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/comment/tests/src/Functional/CommentStatisticsTest.php b/core/modules/comment/tests/src/Functional/CommentStatisticsTest.php
index 57b7ce24011d..eb84b24994c9 100644
--- a/core/modules/comment/tests/src/Functional/CommentStatisticsTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentStatisticsTest.php
@@ -20,6 +20,11 @@ class CommentStatisticsTest extends CommentTestBase {
    */
   protected $webUser2;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/comment/tests/src/Functional/CommentStatusFieldAccessTest.php b/core/modules/comment/tests/src/Functional/CommentStatusFieldAccessTest.php
index d2495d3791c7..7009ea2c33e2 100644
--- a/core/modules/comment/tests/src/Functional/CommentStatusFieldAccessTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentStatusFieldAccessTest.php
@@ -20,6 +20,11 @@ class CommentStatusFieldAccessTest extends BrowserTestBase {
    */
   public $profile = 'testing';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Comment admin.
    *
diff --git a/core/modules/comment/tests/src/Functional/CommentThreadingTest.php b/core/modules/comment/tests/src/Functional/CommentThreadingTest.php
index 2e2b6868f6eb..50217d38c130 100644
--- a/core/modules/comment/tests/src/Functional/CommentThreadingTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentThreadingTest.php
@@ -12,6 +12,11 @@
  */
 class CommentThreadingTest extends CommentTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Tests the comment threading.
    */
diff --git a/core/modules/comment/tests/src/Functional/CommentTitleTest.php b/core/modules/comment/tests/src/Functional/CommentTitleTest.php
index ecf760abce6e..b87b14d34d80 100644
--- a/core/modules/comment/tests/src/Functional/CommentTitleTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentTitleTest.php
@@ -10,6 +10,11 @@
  */
 class CommentTitleTest extends CommentTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Tests markup for comments with empty titles.
    */
diff --git a/core/modules/comment/tests/src/Functional/CommentTokenReplaceTest.php b/core/modules/comment/tests/src/Functional/CommentTokenReplaceTest.php
index 32670f5f1978..b402da57f851 100644
--- a/core/modules/comment/tests/src/Functional/CommentTokenReplaceTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentTokenReplaceTest.php
@@ -26,6 +26,11 @@ class CommentTokenReplaceTest extends CommentTestBase {
    */
   public static $modules = ['taxonomy'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Creates a comment, then tests the tokens generated from it.
    */
diff --git a/core/modules/comment/tests/src/Functional/CommentTranslationUITest.php b/core/modules/comment/tests/src/Functional/CommentTranslationUITest.php
index b6bb692d47cd..8f47909403fa 100644
--- a/core/modules/comment/tests/src/Functional/CommentTranslationUITest.php
+++ b/core/modules/comment/tests/src/Functional/CommentTranslationUITest.php
@@ -16,6 +16,11 @@ class CommentTranslationUITest extends ContentTranslationUITestBase {
 
   use CommentTestTrait;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The subject of the test comment.
    *
diff --git a/core/modules/comment/tests/src/Functional/CommentTypeTest.php b/core/modules/comment/tests/src/Functional/CommentTypeTest.php
index c2eeb928cf84..e13b2f59898e 100644
--- a/core/modules/comment/tests/src/Functional/CommentTypeTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentTypeTest.php
@@ -17,6 +17,11 @@
  */
 class CommentTypeTest extends CommentTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Admin user.
    *
diff --git a/core/modules/comment/tests/src/Functional/Hal/CommentHalJsonAnonTest.php b/core/modules/comment/tests/src/Functional/Hal/CommentHalJsonAnonTest.php
index 723df956012a..01e069623e13 100644
--- a/core/modules/comment/tests/src/Functional/Hal/CommentHalJsonAnonTest.php
+++ b/core/modules/comment/tests/src/Functional/Hal/CommentHalJsonAnonTest.php
@@ -11,6 +11,11 @@ class CommentHalJsonAnonTest extends CommentHalJsonTestBase {
 
   use AnonResourceTestTrait;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    *
diff --git a/core/modules/comment/tests/src/Functional/Hal/CommentHalJsonBasicAuthTest.php b/core/modules/comment/tests/src/Functional/Hal/CommentHalJsonBasicAuthTest.php
index 7d766fdfcacc..0062fe5a4069 100644
--- a/core/modules/comment/tests/src/Functional/Hal/CommentHalJsonBasicAuthTest.php
+++ b/core/modules/comment/tests/src/Functional/Hal/CommentHalJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class CommentHalJsonBasicAuthTest extends CommentHalJsonTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/comment/tests/src/Functional/Hal/CommentHalJsonCookieTest.php b/core/modules/comment/tests/src/Functional/Hal/CommentHalJsonCookieTest.php
index 806cf3fdcc96..dd67cf6f2b7f 100644
--- a/core/modules/comment/tests/src/Functional/Hal/CommentHalJsonCookieTest.php
+++ b/core/modules/comment/tests/src/Functional/Hal/CommentHalJsonCookieTest.php
@@ -16,4 +16,9 @@ class CommentHalJsonCookieTest extends CommentHalJsonTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/comment/tests/src/Functional/Hal/CommentTypeHalJsonAnonTest.php b/core/modules/comment/tests/src/Functional/Hal/CommentTypeHalJsonAnonTest.php
index 179ae1861218..b3a254f8c132 100644
--- a/core/modules/comment/tests/src/Functional/Hal/CommentTypeHalJsonAnonTest.php
+++ b/core/modules/comment/tests/src/Functional/Hal/CommentTypeHalJsonAnonTest.php
@@ -17,6 +17,11 @@ class CommentTypeHalJsonAnonTest extends CommentTypeResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/comment/tests/src/Functional/Hal/CommentTypeHalJsonBasicAuthTest.php b/core/modules/comment/tests/src/Functional/Hal/CommentTypeHalJsonBasicAuthTest.php
index 3a014bd1d19f..ff21f3489c7c 100644
--- a/core/modules/comment/tests/src/Functional/Hal/CommentTypeHalJsonBasicAuthTest.php
+++ b/core/modules/comment/tests/src/Functional/Hal/CommentTypeHalJsonBasicAuthTest.php
@@ -17,6 +17,11 @@ class CommentTypeHalJsonBasicAuthTest extends CommentTypeResourceTestBase {
    */
   public static $modules = ['hal', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/comment/tests/src/Functional/Hal/CommentTypeHalJsonCookieTest.php b/core/modules/comment/tests/src/Functional/Hal/CommentTypeHalJsonCookieTest.php
index 9d6440ead469..0abdeefb67b8 100644
--- a/core/modules/comment/tests/src/Functional/Hal/CommentTypeHalJsonCookieTest.php
+++ b/core/modules/comment/tests/src/Functional/Hal/CommentTypeHalJsonCookieTest.php
@@ -17,6 +17,11 @@ class CommentTypeHalJsonCookieTest extends CommentTypeResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/comment/tests/src/Functional/Rest/CommentJsonAnonTest.php b/core/modules/comment/tests/src/Functional/Rest/CommentJsonAnonTest.php
index 54925dd98374..8c54ec12863b 100644
--- a/core/modules/comment/tests/src/Functional/Rest/CommentJsonAnonTest.php
+++ b/core/modules/comment/tests/src/Functional/Rest/CommentJsonAnonTest.php
@@ -21,6 +21,11 @@ class CommentJsonAnonTest extends CommentResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    *
diff --git a/core/modules/comment/tests/src/Functional/Rest/CommentJsonBasicAuthTest.php b/core/modules/comment/tests/src/Functional/Rest/CommentJsonBasicAuthTest.php
index a4f72551a47b..92d16fb4b188 100644
--- a/core/modules/comment/tests/src/Functional/Rest/CommentJsonBasicAuthTest.php
+++ b/core/modules/comment/tests/src/Functional/Rest/CommentJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class CommentJsonBasicAuthTest extends CommentResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/comment/tests/src/Functional/Rest/CommentJsonCookieTest.php b/core/modules/comment/tests/src/Functional/Rest/CommentJsonCookieTest.php
index f2c78a25a257..846335acc3eb 100644
--- a/core/modules/comment/tests/src/Functional/Rest/CommentJsonCookieTest.php
+++ b/core/modules/comment/tests/src/Functional/Rest/CommentJsonCookieTest.php
@@ -26,4 +26,9 @@ class CommentJsonCookieTest extends CommentResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/comment/tests/src/Functional/Rest/CommentTypeJsonAnonTest.php b/core/modules/comment/tests/src/Functional/Rest/CommentTypeJsonAnonTest.php
index 496e20aa6021..fd7f14000d05 100644
--- a/core/modules/comment/tests/src/Functional/Rest/CommentTypeJsonAnonTest.php
+++ b/core/modules/comment/tests/src/Functional/Rest/CommentTypeJsonAnonTest.php
@@ -21,4 +21,9 @@ class CommentTypeJsonAnonTest extends CommentTypeResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/comment/tests/src/Functional/Rest/CommentTypeJsonBasicAuthTest.php b/core/modules/comment/tests/src/Functional/Rest/CommentTypeJsonBasicAuthTest.php
index c947dbc92c61..14fb9c9a050b 100644
--- a/core/modules/comment/tests/src/Functional/Rest/CommentTypeJsonBasicAuthTest.php
+++ b/core/modules/comment/tests/src/Functional/Rest/CommentTypeJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class CommentTypeJsonBasicAuthTest extends CommentTypeResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/comment/tests/src/Functional/Rest/CommentTypeJsonCookieTest.php b/core/modules/comment/tests/src/Functional/Rest/CommentTypeJsonCookieTest.php
index ddbdf27ccb2b..4fe56f1d4fa1 100644
--- a/core/modules/comment/tests/src/Functional/Rest/CommentTypeJsonCookieTest.php
+++ b/core/modules/comment/tests/src/Functional/Rest/CommentTypeJsonCookieTest.php
@@ -26,4 +26,9 @@ class CommentTypeJsonCookieTest extends CommentTypeResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/comment/tests/src/Functional/Rest/CommentTypeXmlAnonTest.php b/core/modules/comment/tests/src/Functional/Rest/CommentTypeXmlAnonTest.php
index 96d6c41a0edb..fed57acaacbe 100644
--- a/core/modules/comment/tests/src/Functional/Rest/CommentTypeXmlAnonTest.php
+++ b/core/modules/comment/tests/src/Functional/Rest/CommentTypeXmlAnonTest.php
@@ -23,4 +23,9 @@ class CommentTypeXmlAnonTest extends CommentTypeResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/comment/tests/src/Functional/Rest/CommentTypeXmlBasicAuthTest.php b/core/modules/comment/tests/src/Functional/Rest/CommentTypeXmlBasicAuthTest.php
index e92f2bcc65da..a1fc840eec4e 100644
--- a/core/modules/comment/tests/src/Functional/Rest/CommentTypeXmlBasicAuthTest.php
+++ b/core/modules/comment/tests/src/Functional/Rest/CommentTypeXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class CommentTypeXmlBasicAuthTest extends CommentTypeResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/comment/tests/src/Functional/Rest/CommentTypeXmlCookieTest.php b/core/modules/comment/tests/src/Functional/Rest/CommentTypeXmlCookieTest.php
index 01f42db448da..fa16de1a45a4 100644
--- a/core/modules/comment/tests/src/Functional/Rest/CommentTypeXmlCookieTest.php
+++ b/core/modules/comment/tests/src/Functional/Rest/CommentTypeXmlCookieTest.php
@@ -28,4 +28,9 @@ class CommentTypeXmlCookieTest extends CommentTypeResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/comment/tests/src/Functional/Rest/CommentXmlAnonTest.php b/core/modules/comment/tests/src/Functional/Rest/CommentXmlAnonTest.php
index 22c1b858f5e3..1950cbabf375 100644
--- a/core/modules/comment/tests/src/Functional/Rest/CommentXmlAnonTest.php
+++ b/core/modules/comment/tests/src/Functional/Rest/CommentXmlAnonTest.php
@@ -23,6 +23,11 @@ class CommentXmlAnonTest extends CommentResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    *
diff --git a/core/modules/comment/tests/src/Functional/Rest/CommentXmlBasicAuthTest.php b/core/modules/comment/tests/src/Functional/Rest/CommentXmlBasicAuthTest.php
index d1f38e44a4b3..90f4eacdd64e 100644
--- a/core/modules/comment/tests/src/Functional/Rest/CommentXmlBasicAuthTest.php
+++ b/core/modules/comment/tests/src/Functional/Rest/CommentXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class CommentXmlBasicAuthTest extends CommentResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/comment/tests/src/Functional/Rest/CommentXmlCookieTest.php b/core/modules/comment/tests/src/Functional/Rest/CommentXmlCookieTest.php
index e06cf2652183..57631e1880f1 100644
--- a/core/modules/comment/tests/src/Functional/Rest/CommentXmlCookieTest.php
+++ b/core/modules/comment/tests/src/Functional/Rest/CommentXmlCookieTest.php
@@ -28,6 +28,11 @@ class CommentXmlCookieTest extends CommentResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/comment/tests/src/Functional/Views/CommentAdminTest.php b/core/modules/comment/tests/src/Functional/Views/CommentAdminTest.php
index ee42dcaddd07..a31ad265926a 100644
--- a/core/modules/comment/tests/src/Functional/Views/CommentAdminTest.php
+++ b/core/modules/comment/tests/src/Functional/Views/CommentAdminTest.php
@@ -20,6 +20,11 @@
  */
 class CommentAdminTest extends CommentBrowserTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/comment/tests/src/Functional/Views/CommentFieldFilterTest.php b/core/modules/comment/tests/src/Functional/Views/CommentFieldFilterTest.php
index dabacc3bed25..18bfde335434 100644
--- a/core/modules/comment/tests/src/Functional/Views/CommentFieldFilterTest.php
+++ b/core/modules/comment/tests/src/Functional/Views/CommentFieldFilterTest.php
@@ -17,6 +17,11 @@ class CommentFieldFilterTest extends CommentTestBase {
    */
   public static $modules = ['language'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/comment/tests/src/Functional/Views/CommentOperationsTest.php b/core/modules/comment/tests/src/Functional/Views/CommentOperationsTest.php
index 4bef37edc2d4..ecd15d2a97ff 100644
--- a/core/modules/comment/tests/src/Functional/Views/CommentOperationsTest.php
+++ b/core/modules/comment/tests/src/Functional/Views/CommentOperationsTest.php
@@ -16,6 +16,11 @@ class CommentOperationsTest extends CommentTestBase {
    */
   public static $testViews = ['test_comment_operations'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Test the operations field plugin.
    */
diff --git a/core/modules/comment/tests/src/Functional/Views/CommentRestExportTest.php b/core/modules/comment/tests/src/Functional/Views/CommentRestExportTest.php
index 908a86a3592e..d5046a396ed9 100644
--- a/core/modules/comment/tests/src/Functional/Views/CommentRestExportTest.php
+++ b/core/modules/comment/tests/src/Functional/Views/CommentRestExportTest.php
@@ -12,6 +12,11 @@
  */
 class CommentRestExportTest extends CommentTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/comment/tests/src/Functional/Views/CommentRowTest.php b/core/modules/comment/tests/src/Functional/Views/CommentRowTest.php
index 7cf3ef3b2416..8cf2121a5eac 100644
--- a/core/modules/comment/tests/src/Functional/Views/CommentRowTest.php
+++ b/core/modules/comment/tests/src/Functional/Views/CommentRowTest.php
@@ -9,6 +9,11 @@
  */
 class CommentRowTest extends CommentTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/comment/tests/src/Functional/Views/DefaultViewRecentCommentsTest.php b/core/modules/comment/tests/src/Functional/Views/DefaultViewRecentCommentsTest.php
index 9ba4d85e77d6..b6f98a0dd23a 100644
--- a/core/modules/comment/tests/src/Functional/Views/DefaultViewRecentCommentsTest.php
+++ b/core/modules/comment/tests/src/Functional/Views/DefaultViewRecentCommentsTest.php
@@ -25,6 +25,11 @@ class DefaultViewRecentCommentsTest extends ViewTestBase {
    */
   public static $modules = ['node', 'comment', 'block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Number of results for the Master display.
    *
diff --git a/core/modules/comment/tests/src/Functional/Views/NodeCommentsTest.php b/core/modules/comment/tests/src/Functional/Views/NodeCommentsTest.php
index e2c5d15ef51f..02c91f4ed5d6 100644
--- a/core/modules/comment/tests/src/Functional/Views/NodeCommentsTest.php
+++ b/core/modules/comment/tests/src/Functional/Views/NodeCommentsTest.php
@@ -16,6 +16,11 @@ class NodeCommentsTest extends CommentTestBase {
    */
   public static $modules = ['history'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/comment/tests/src/Functional/Views/RowRssTest.php b/core/modules/comment/tests/src/Functional/Views/RowRssTest.php
index 7d61852ef8b6..f8a24afa4e87 100644
--- a/core/modules/comment/tests/src/Functional/Views/RowRssTest.php
+++ b/core/modules/comment/tests/src/Functional/Views/RowRssTest.php
@@ -10,6 +10,11 @@
  */
 class RowRssTest extends CommentTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/comment/tests/src/Functional/Views/WizardTest.php b/core/modules/comment/tests/src/Functional/Views/WizardTest.php
index 73332a87dfd1..6ae5c1127007 100644
--- a/core/modules/comment/tests/src/Functional/Views/WizardTest.php
+++ b/core/modules/comment/tests/src/Functional/Views/WizardTest.php
@@ -23,6 +23,11 @@ class WizardTest extends WizardTestBase {
    */
   public static $modules = ['node', 'comment'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/config/tests/config_test/tests/src/Functional/Hal/ConfigTestHalJsonAnonTest.php b/core/modules/config/tests/config_test/tests/src/Functional/Hal/ConfigTestHalJsonAnonTest.php
index d874f45f263c..8e20d7259115 100644
--- a/core/modules/config/tests/config_test/tests/src/Functional/Hal/ConfigTestHalJsonAnonTest.php
+++ b/core/modules/config/tests/config_test/tests/src/Functional/Hal/ConfigTestHalJsonAnonTest.php
@@ -17,6 +17,11 @@ class ConfigTestHalJsonAnonTest extends ConfigTestResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/config/tests/config_test/tests/src/Functional/Hal/ConfigTestHalJsonBasicAuthTest.php b/core/modules/config/tests/config_test/tests/src/Functional/Hal/ConfigTestHalJsonBasicAuthTest.php
index 01a69c329d8b..f8adc1d563fd 100644
--- a/core/modules/config/tests/config_test/tests/src/Functional/Hal/ConfigTestHalJsonBasicAuthTest.php
+++ b/core/modules/config/tests/config_test/tests/src/Functional/Hal/ConfigTestHalJsonBasicAuthTest.php
@@ -17,6 +17,11 @@ class ConfigTestHalJsonBasicAuthTest extends ConfigTestResourceTestBase {
    */
   public static $modules = ['hal', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/config/tests/config_test/tests/src/Functional/Hal/ConfigTestHalJsonCookieTest.php b/core/modules/config/tests/config_test/tests/src/Functional/Hal/ConfigTestHalJsonCookieTest.php
index eb670d2a4ef7..a0f8dc1f3c20 100644
--- a/core/modules/config/tests/config_test/tests/src/Functional/Hal/ConfigTestHalJsonCookieTest.php
+++ b/core/modules/config/tests/config_test/tests/src/Functional/Hal/ConfigTestHalJsonCookieTest.php
@@ -17,6 +17,11 @@ class ConfigTestHalJsonCookieTest extends ConfigTestResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/config/tests/config_test/tests/src/Functional/Rest/ConfigTestJsonAnonTest.php b/core/modules/config/tests/config_test/tests/src/Functional/Rest/ConfigTestJsonAnonTest.php
index 0121b1f3a4c4..e284f9dad275 100644
--- a/core/modules/config/tests/config_test/tests/src/Functional/Rest/ConfigTestJsonAnonTest.php
+++ b/core/modules/config/tests/config_test/tests/src/Functional/Rest/ConfigTestJsonAnonTest.php
@@ -21,4 +21,9 @@ class ConfigTestJsonAnonTest extends ConfigTestResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/config/tests/config_test/tests/src/Functional/Rest/ConfigTestJsonBasicAuthTest.php b/core/modules/config/tests/config_test/tests/src/Functional/Rest/ConfigTestJsonBasicAuthTest.php
index 87c415840a1d..724effcc9ab1 100644
--- a/core/modules/config/tests/config_test/tests/src/Functional/Rest/ConfigTestJsonBasicAuthTest.php
+++ b/core/modules/config/tests/config_test/tests/src/Functional/Rest/ConfigTestJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class ConfigTestJsonBasicAuthTest extends ConfigTestResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/config/tests/config_test/tests/src/Functional/Rest/ConfigTestJsonCookieTest.php b/core/modules/config/tests/config_test/tests/src/Functional/Rest/ConfigTestJsonCookieTest.php
index 173d7613325d..97efc5852a22 100644
--- a/core/modules/config/tests/config_test/tests/src/Functional/Rest/ConfigTestJsonCookieTest.php
+++ b/core/modules/config/tests/config_test/tests/src/Functional/Rest/ConfigTestJsonCookieTest.php
@@ -26,4 +26,9 @@ class ConfigTestJsonCookieTest extends ConfigTestResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/config/tests/config_test/tests/src/Functional/Rest/ConfigTestXmlAnonTest.php b/core/modules/config/tests/config_test/tests/src/Functional/Rest/ConfigTestXmlAnonTest.php
index 451e86df2244..05c1341903fc 100644
--- a/core/modules/config/tests/config_test/tests/src/Functional/Rest/ConfigTestXmlAnonTest.php
+++ b/core/modules/config/tests/config_test/tests/src/Functional/Rest/ConfigTestXmlAnonTest.php
@@ -23,4 +23,9 @@ class ConfigTestXmlAnonTest extends ConfigTestResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/config/tests/config_test/tests/src/Functional/Rest/ConfigTestXmlBasicAuthTest.php b/core/modules/config/tests/config_test/tests/src/Functional/Rest/ConfigTestXmlBasicAuthTest.php
index c65028f212ba..f253c383472e 100644
--- a/core/modules/config/tests/config_test/tests/src/Functional/Rest/ConfigTestXmlBasicAuthTest.php
+++ b/core/modules/config/tests/config_test/tests/src/Functional/Rest/ConfigTestXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class ConfigTestXmlBasicAuthTest extends ConfigTestResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/config/tests/config_test/tests/src/Functional/Rest/ConfigTestXmlCookieTest.php b/core/modules/config/tests/config_test/tests/src/Functional/Rest/ConfigTestXmlCookieTest.php
index 540b14e8d36b..3be09e2e7843 100644
--- a/core/modules/config/tests/config_test/tests/src/Functional/Rest/ConfigTestXmlCookieTest.php
+++ b/core/modules/config/tests/config_test/tests/src/Functional/Rest/ConfigTestXmlCookieTest.php
@@ -28,4 +28,9 @@ class ConfigTestXmlCookieTest extends ConfigTestResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/config/tests/src/Functional/CacheabilityMetadataConfigOverrideIntegrationTest.php b/core/modules/config/tests/src/Functional/CacheabilityMetadataConfigOverrideIntegrationTest.php
index 433d288e51fe..496dbbc874ee 100644
--- a/core/modules/config/tests/src/Functional/CacheabilityMetadataConfigOverrideIntegrationTest.php
+++ b/core/modules/config/tests/src/Functional/CacheabilityMetadataConfigOverrideIntegrationTest.php
@@ -22,6 +22,11 @@ class CacheabilityMetadataConfigOverrideIntegrationTest extends BrowserTestBase
     'config_override_integration_test',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/config/tests/src/Functional/ConfigDependencyWebTest.php b/core/modules/config/tests/src/Functional/ConfigDependencyWebTest.php
index 8c8637bda78f..8866d67e1d7e 100644
--- a/core/modules/config/tests/src/Functional/ConfigDependencyWebTest.php
+++ b/core/modules/config/tests/src/Functional/ConfigDependencyWebTest.php
@@ -24,6 +24,11 @@ class ConfigDependencyWebTest extends BrowserTestBase {
    */
   public static $modules = ['config_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests ConfigDependencyDeleteFormTrait.
    *
diff --git a/core/modules/config/tests/src/Functional/ConfigDraggableListBuilderTest.php b/core/modules/config/tests/src/Functional/ConfigDraggableListBuilderTest.php
index 74829359a108..a9effb4b0fcf 100644
--- a/core/modules/config/tests/src/Functional/ConfigDraggableListBuilderTest.php
+++ b/core/modules/config/tests/src/Functional/ConfigDraggableListBuilderTest.php
@@ -17,6 +17,11 @@ class ConfigDraggableListBuilderTest extends BrowserTestBase {
    */
   public static $modules = ['config_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test draggable lists.
    */
diff --git a/core/modules/config/tests/src/Functional/ConfigEntityFormOverrideTest.php b/core/modules/config/tests/src/Functional/ConfigEntityFormOverrideTest.php
index 27610616dd89..628fb4bf826d 100644
--- a/core/modules/config/tests/src/Functional/ConfigEntityFormOverrideTest.php
+++ b/core/modules/config/tests/src/Functional/ConfigEntityFormOverrideTest.php
@@ -16,6 +16,11 @@ class ConfigEntityFormOverrideTest extends BrowserTestBase {
    */
   public static $modules = ['config_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that overrides do not affect forms or listing screens.
    */
diff --git a/core/modules/config/tests/src/Functional/ConfigEntityListMultilingualTest.php b/core/modules/config/tests/src/Functional/ConfigEntityListMultilingualTest.php
index cf9ff99f221e..882190a9c063 100644
--- a/core/modules/config/tests/src/Functional/ConfigEntityListMultilingualTest.php
+++ b/core/modules/config/tests/src/Functional/ConfigEntityListMultilingualTest.php
@@ -19,6 +19,11 @@ class ConfigEntityListMultilingualTest extends BrowserTestBase {
    */
   public static $modules = ['config_test', 'language', 'block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/config/tests/src/Functional/ConfigEntityListTest.php b/core/modules/config/tests/src/Functional/ConfigEntityListTest.php
index ec8f88aa5db4..673223f494f6 100644
--- a/core/modules/config/tests/src/Functional/ConfigEntityListTest.php
+++ b/core/modules/config/tests/src/Functional/ConfigEntityListTest.php
@@ -23,6 +23,11 @@ class ConfigEntityListTest extends BrowserTestBase {
    */
   public static $modules = ['block', 'config_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/config/tests/src/Functional/ConfigEntityStatusUITest.php b/core/modules/config/tests/src/Functional/ConfigEntityStatusUITest.php
index b0fa22f2dec9..c987551449b1 100644
--- a/core/modules/config/tests/src/Functional/ConfigEntityStatusUITest.php
+++ b/core/modules/config/tests/src/Functional/ConfigEntityStatusUITest.php
@@ -18,6 +18,11 @@ class ConfigEntityStatusUITest extends BrowserTestBase {
    */
   public static $modules = ['config_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests status operations.
    */
diff --git a/core/modules/config/tests/src/Functional/ConfigEntityTest.php b/core/modules/config/tests/src/Functional/ConfigEntityTest.php
index e18d2cdfce02..2606ae8b92b2 100644
--- a/core/modules/config/tests/src/Functional/ConfigEntityTest.php
+++ b/core/modules/config/tests/src/Functional/ConfigEntityTest.php
@@ -29,6 +29,11 @@ class ConfigEntityTest extends BrowserTestBase {
    */
   public static $modules = ['config_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests CRUD operations.
    */
diff --git a/core/modules/config/tests/src/Functional/ConfigExportImportUITest.php b/core/modules/config/tests/src/Functional/ConfigExportImportUITest.php
index 4e20768ab35a..9a6c3525be96 100644
--- a/core/modules/config/tests/src/Functional/ConfigExportImportUITest.php
+++ b/core/modules/config/tests/src/Functional/ConfigExportImportUITest.php
@@ -68,6 +68,11 @@ class ConfigExportImportUITest extends BrowserTestBase {
    */
   public static $modules = ['config', 'node', 'field'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/config/tests/src/Functional/ConfigExportUITest.php b/core/modules/config/tests/src/Functional/ConfigExportUITest.php
index 215b582bf645..ba88e6d2d1ae 100644
--- a/core/modules/config/tests/src/Functional/ConfigExportUITest.php
+++ b/core/modules/config/tests/src/Functional/ConfigExportUITest.php
@@ -21,6 +21,11 @@ class ConfigExportUITest extends BrowserTestBase {
    */
   public static $modules = ['config', 'config_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/config/tests/src/Functional/ConfigFormOverrideTest.php b/core/modules/config/tests/src/Functional/ConfigFormOverrideTest.php
index 3bba16daa75c..14edd8838685 100644
--- a/core/modules/config/tests/src/Functional/ConfigFormOverrideTest.php
+++ b/core/modules/config/tests/src/Functional/ConfigFormOverrideTest.php
@@ -12,6 +12,11 @@
  */
 class ConfigFormOverrideTest extends BrowserTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that overrides do not affect forms.
    */
diff --git a/core/modules/config/tests/src/Functional/ConfigImportInstallProfileTest.php b/core/modules/config/tests/src/Functional/ConfigImportInstallProfileTest.php
index 8b0787d6ee02..66bf8a9a6aff 100644
--- a/core/modules/config/tests/src/Functional/ConfigImportInstallProfileTest.php
+++ b/core/modules/config/tests/src/Functional/ConfigImportInstallProfileTest.php
@@ -25,6 +25,11 @@ class ConfigImportInstallProfileTest extends BrowserTestBase {
    */
   public static $modules = ['config'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with the 'synchronize configuration' permission.
    *
diff --git a/core/modules/config/tests/src/Functional/ConfigImportUITest.php b/core/modules/config/tests/src/Functional/ConfigImportUITest.php
index 3786b5155750..bcad9eeb6661 100644
--- a/core/modules/config/tests/src/Functional/ConfigImportUITest.php
+++ b/core/modules/config/tests/src/Functional/ConfigImportUITest.php
@@ -21,6 +21,11 @@ class ConfigImportUITest extends BrowserTestBase {
    */
   public static $modules = ['config', 'config_test', 'config_import_test', 'text', 'options'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * A user with the 'synchronize configuration' permission.
    *
diff --git a/core/modules/config/tests/src/Functional/ConfigImportUploadTest.php b/core/modules/config/tests/src/Functional/ConfigImportUploadTest.php
index bc4dc7c5c32a..ed62bd12e9b8 100644
--- a/core/modules/config/tests/src/Functional/ConfigImportUploadTest.php
+++ b/core/modules/config/tests/src/Functional/ConfigImportUploadTest.php
@@ -29,6 +29,11 @@ class ConfigImportUploadTest extends BrowserTestBase {
    */
   public static $modules = ['config'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/config/tests/src/Functional/ConfigInstallProfileOverrideTest.php b/core/modules/config/tests/src/Functional/ConfigInstallProfileOverrideTest.php
index 3a151b574dd6..80a6861b3305 100644
--- a/core/modules/config/tests/src/Functional/ConfigInstallProfileOverrideTest.php
+++ b/core/modules/config/tests/src/Functional/ConfigInstallProfileOverrideTest.php
@@ -26,6 +26,11 @@ class ConfigInstallProfileOverrideTest extends BrowserTestBase {
    */
   protected $profile = 'testing_config_overrides';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests install profile config changes.
    */
diff --git a/core/modules/config/tests/src/Functional/ConfigInstallProfileUnmetDependenciesTest.php b/core/modules/config/tests/src/Functional/ConfigInstallProfileUnmetDependenciesTest.php
index 59f9f706ee70..b9ae7bc5c94e 100644
--- a/core/modules/config/tests/src/Functional/ConfigInstallProfileUnmetDependenciesTest.php
+++ b/core/modules/config/tests/src/Functional/ConfigInstallProfileUnmetDependenciesTest.php
@@ -27,6 +27,11 @@ class ConfigInstallProfileUnmetDependenciesTest extends InstallerTestBase {
    */
   protected $expectedException = FALSE;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/config/tests/src/Functional/ConfigInstallWebTest.php b/core/modules/config/tests/src/Functional/ConfigInstallWebTest.php
index 5f7c87d01378..1496beeb2de7 100644
--- a/core/modules/config/tests/src/Functional/ConfigInstallWebTest.php
+++ b/core/modules/config/tests/src/Functional/ConfigInstallWebTest.php
@@ -22,6 +22,11 @@ class ConfigInstallWebTest extends BrowserTestBase {
    */
   protected $adminUser;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/config/tests/src/Functional/ConfigLanguageOverrideWebTest.php b/core/modules/config/tests/src/Functional/ConfigLanguageOverrideWebTest.php
index c7e0b27d4448..b67d2b9400ab 100644
--- a/core/modules/config/tests/src/Functional/ConfigLanguageOverrideWebTest.php
+++ b/core/modules/config/tests/src/Functional/ConfigLanguageOverrideWebTest.php
@@ -24,6 +24,11 @@ class ConfigLanguageOverrideWebTest extends BrowserTestBase {
     'system',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/config/tests/src/Functional/ConfigOtherModuleTest.php b/core/modules/config/tests/src/Functional/ConfigOtherModuleTest.php
index 4ff2b18f80bc..d44baf7e8234 100644
--- a/core/modules/config/tests/src/Functional/ConfigOtherModuleTest.php
+++ b/core/modules/config/tests/src/Functional/ConfigOtherModuleTest.php
@@ -11,6 +11,11 @@
  */
 class ConfigOtherModuleTest extends BrowserTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests enabling the provider of the default configuration first.
    */
diff --git a/core/modules/config/tests/src/Functional/ConfigSingleImportExportTest.php b/core/modules/config/tests/src/Functional/ConfigSingleImportExportTest.php
index 8c5491b0b6fa..c80af8d9e6b9 100644
--- a/core/modules/config/tests/src/Functional/ConfigSingleImportExportTest.php
+++ b/core/modules/config/tests/src/Functional/ConfigSingleImportExportTest.php
@@ -26,6 +26,11 @@ class ConfigSingleImportExportTest extends BrowserTestBase {
     'language',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/config/tests/src/Functional/LanguageNegotiationFormOverrideTest.php b/core/modules/config/tests/src/Functional/LanguageNegotiationFormOverrideTest.php
index 6c4e1bb3118a..0aa15ea1ea38 100644
--- a/core/modules/config/tests/src/Functional/LanguageNegotiationFormOverrideTest.php
+++ b/core/modules/config/tests/src/Functional/LanguageNegotiationFormOverrideTest.php
@@ -14,6 +14,11 @@ class LanguageNegotiationFormOverrideTest extends BrowserTestBase {
 
   public static $modules = ['language', 'locale', 'locale_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that overrides do not affect language-negotiation form values.
    */
diff --git a/core/modules/config/tests/src/Functional/SchemaConfigListenerWebTest.php b/core/modules/config/tests/src/Functional/SchemaConfigListenerWebTest.php
index 6d221e26ddc1..588db76a331e 100644
--- a/core/modules/config/tests/src/Functional/SchemaConfigListenerWebTest.php
+++ b/core/modules/config/tests/src/Functional/SchemaConfigListenerWebTest.php
@@ -17,6 +17,11 @@ class SchemaConfigListenerWebTest extends BrowserTestBase {
    */
   public static $modules = ['config_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests \Drupal\Core\Config\Development\ConfigSchemaChecker.
    */
diff --git a/core/modules/config/tests/src/Functional/TransformedConfigExportImportUITest.php b/core/modules/config/tests/src/Functional/TransformedConfigExportImportUITest.php
index b87d12a16dc4..ce7f160d58ba 100644
--- a/core/modules/config/tests/src/Functional/TransformedConfigExportImportUITest.php
+++ b/core/modules/config/tests/src/Functional/TransformedConfigExportImportUITest.php
@@ -20,6 +20,11 @@ class TransformedConfigExportImportUITest extends BrowserTestBase {
     'config_transformer_test',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/config/tests/src/FunctionalJavascript/ConfigEntityTest.php b/core/modules/config/tests/src/FunctionalJavascript/ConfigEntityTest.php
index f7e6dc8ff528..7ea62e2e90f1 100644
--- a/core/modules/config/tests/src/FunctionalJavascript/ConfigEntityTest.php
+++ b/core/modules/config/tests/src/FunctionalJavascript/ConfigEntityTest.php
@@ -16,6 +16,11 @@ class ConfigEntityTest extends WebDriverTestBase {
    */
   public static $modules = ['config_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests ajax operations through the UI on 'Add' page.
    */
diff --git a/core/modules/config_translation/tests/src/Functional/ConfigTranslationCacheTest.php b/core/modules/config_translation/tests/src/Functional/ConfigTranslationCacheTest.php
index 0def24a490b4..7b64987605c4 100644
--- a/core/modules/config_translation/tests/src/Functional/ConfigTranslationCacheTest.php
+++ b/core/modules/config_translation/tests/src/Functional/ConfigTranslationCacheTest.php
@@ -37,6 +37,11 @@ class ConfigTranslationCacheTest extends BrowserTestBase {
     'views_ui',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Languages to enable.
    *
diff --git a/core/modules/config_translation/tests/src/Functional/ConfigTranslationDateFormatUiTest.php b/core/modules/config_translation/tests/src/Functional/ConfigTranslationDateFormatUiTest.php
index 7cbeb57746a7..c0c88738510d 100644
--- a/core/modules/config_translation/tests/src/Functional/ConfigTranslationDateFormatUiTest.php
+++ b/core/modules/config_translation/tests/src/Functional/ConfigTranslationDateFormatUiTest.php
@@ -18,6 +18,11 @@ class ConfigTranslationDateFormatUiTest extends BrowserTestBase {
     'system',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/config_translation/tests/src/Functional/ConfigTranslationListUiTest.php b/core/modules/config_translation/tests/src/Functional/ConfigTranslationListUiTest.php
index 1d0116dc9997..7b1ca0ef86ab 100644
--- a/core/modules/config_translation/tests/src/Functional/ConfigTranslationListUiTest.php
+++ b/core/modules/config_translation/tests/src/Functional/ConfigTranslationListUiTest.php
@@ -41,6 +41,11 @@ class ConfigTranslationListUiTest extends BrowserTestBase {
     'toolbar',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Admin user with all needed permissions.
    *
diff --git a/core/modules/config_translation/tests/src/Functional/ConfigTranslationOverviewTest.php b/core/modules/config_translation/tests/src/Functional/ConfigTranslationOverviewTest.php
index 45f6636b37cd..d5647d45a411 100644
--- a/core/modules/config_translation/tests/src/Functional/ConfigTranslationOverviewTest.php
+++ b/core/modules/config_translation/tests/src/Functional/ConfigTranslationOverviewTest.php
@@ -30,6 +30,11 @@ class ConfigTranslationOverviewTest extends BrowserTestBase {
     'views_ui',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Languages to enable.
    *
diff --git a/core/modules/config_translation/tests/src/Functional/ConfigTranslationUiTest.php b/core/modules/config_translation/tests/src/Functional/ConfigTranslationUiTest.php
index 748a9ecabfb0..bb5e218191a6 100644
--- a/core/modules/config_translation/tests/src/Functional/ConfigTranslationUiTest.php
+++ b/core/modules/config_translation/tests/src/Functional/ConfigTranslationUiTest.php
@@ -46,6 +46,11 @@ class ConfigTranslationUiTest extends BrowserTestBase {
     'views_ui',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Languages to enable.
    *
diff --git a/core/modules/config_translation/tests/src/Functional/ConfigTranslationUiThemeTest.php b/core/modules/config_translation/tests/src/Functional/ConfigTranslationUiThemeTest.php
index dcfb7916fe85..6754420c1c57 100644
--- a/core/modules/config_translation/tests/src/Functional/ConfigTranslationUiThemeTest.php
+++ b/core/modules/config_translation/tests/src/Functional/ConfigTranslationUiThemeTest.php
@@ -19,6 +19,11 @@ class ConfigTranslationUiThemeTest extends BrowserTestBase {
    */
   public static $modules = ['config_translation', 'config_translation_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Languages to enable.
    *
diff --git a/core/modules/config_translation/tests/src/Functional/ConfigTranslationViewListUiTest.php b/core/modules/config_translation/tests/src/Functional/ConfigTranslationViewListUiTest.php
index edb41f9ad441..230ffd3aaa0c 100644
--- a/core/modules/config_translation/tests/src/Functional/ConfigTranslationViewListUiTest.php
+++ b/core/modules/config_translation/tests/src/Functional/ConfigTranslationViewListUiTest.php
@@ -25,6 +25,11 @@ class ConfigTranslationViewListUiTest extends UITestBase {
    */
   public static $modules = ['config_translation', 'views_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp($import_test_views = TRUE) {
     parent::setUp($import_test_views);
 
diff --git a/core/modules/config_translation/tests/src/FunctionalJavascript/ConfigTranslationUiTest.php b/core/modules/config_translation/tests/src/FunctionalJavascript/ConfigTranslationUiTest.php
index 585d2d1d38d0..0261663a460b 100644
--- a/core/modules/config_translation/tests/src/FunctionalJavascript/ConfigTranslationUiTest.php
+++ b/core/modules/config_translation/tests/src/FunctionalJavascript/ConfigTranslationUiTest.php
@@ -22,6 +22,11 @@ class ConfigTranslationUiTest extends WebDriverTestBase {
     'views_ui',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that contextual link related to views.
    */
diff --git a/core/modules/contact/tests/src/Functional/ContactLanguageTest.php b/core/modules/contact/tests/src/Functional/ContactLanguageTest.php
index 0c34884503c1..2f08a9f40b9a 100644
--- a/core/modules/contact/tests/src/Functional/ContactLanguageTest.php
+++ b/core/modules/contact/tests/src/Functional/ContactLanguageTest.php
@@ -26,6 +26,11 @@ class ContactLanguageTest extends BrowserTestBase {
     'contact_test',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/contact/tests/src/Functional/ContactPersonalTest.php b/core/modules/contact/tests/src/Functional/ContactPersonalTest.php
index 2c8fae5b5a0a..680d1239db31 100644
--- a/core/modules/contact/tests/src/Functional/ContactPersonalTest.php
+++ b/core/modules/contact/tests/src/Functional/ContactPersonalTest.php
@@ -27,6 +27,11 @@ class ContactPersonalTest extends BrowserTestBase {
    */
   public static $modules = ['contact', 'dblog'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with some administrative permissions.
    *
diff --git a/core/modules/contact/tests/src/Functional/ContactSitewideTest.php b/core/modules/contact/tests/src/Functional/ContactSitewideTest.php
index aef0aa657498..5093a545c5b3 100644
--- a/core/modules/contact/tests/src/Functional/ContactSitewideTest.php
+++ b/core/modules/contact/tests/src/Functional/ContactSitewideTest.php
@@ -31,6 +31,11 @@ class ContactSitewideTest extends BrowserTestBase {
    */
   public static $modules = ['text', 'contact', 'field_ui', 'contact_test', 'block', 'error_service_test', 'dblog'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/contact/tests/src/Functional/ContactStorageTest.php b/core/modules/contact/tests/src/Functional/ContactStorageTest.php
index fbd938bb8a55..ac964f935362 100644
--- a/core/modules/contact/tests/src/Functional/ContactStorageTest.php
+++ b/core/modules/contact/tests/src/Functional/ContactStorageTest.php
@@ -31,6 +31,11 @@ class ContactStorageTest extends ContactSitewideTest {
     'contact_test',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Tests configuration options and the site-wide contact form.
    */
diff --git a/core/modules/contact/tests/src/Functional/Hal/ContactFormHalJsonAnonTest.php b/core/modules/contact/tests/src/Functional/Hal/ContactFormHalJsonAnonTest.php
index e863c978dd1f..4a9babde3378 100644
--- a/core/modules/contact/tests/src/Functional/Hal/ContactFormHalJsonAnonTest.php
+++ b/core/modules/contact/tests/src/Functional/Hal/ContactFormHalJsonAnonTest.php
@@ -17,6 +17,11 @@ class ContactFormHalJsonAnonTest extends ContactFormResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/contact/tests/src/Functional/Hal/ContactFormHalJsonBasicAuthTest.php b/core/modules/contact/tests/src/Functional/Hal/ContactFormHalJsonBasicAuthTest.php
index 7280cfdc7e90..36d867235fcf 100644
--- a/core/modules/contact/tests/src/Functional/Hal/ContactFormHalJsonBasicAuthTest.php
+++ b/core/modules/contact/tests/src/Functional/Hal/ContactFormHalJsonBasicAuthTest.php
@@ -17,6 +17,11 @@ class ContactFormHalJsonBasicAuthTest extends ContactFormResourceTestBase {
    */
   public static $modules = ['hal', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/contact/tests/src/Functional/Hal/ContactFormHalJsonCookieTest.php b/core/modules/contact/tests/src/Functional/Hal/ContactFormHalJsonCookieTest.php
index 2592ae761445..d61e132a1abd 100644
--- a/core/modules/contact/tests/src/Functional/Hal/ContactFormHalJsonCookieTest.php
+++ b/core/modules/contact/tests/src/Functional/Hal/ContactFormHalJsonCookieTest.php
@@ -17,6 +17,11 @@ class ContactFormHalJsonCookieTest extends ContactFormResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/contact/tests/src/Functional/Hal/MessageHalJsonAnonTest.php b/core/modules/contact/tests/src/Functional/Hal/MessageHalJsonAnonTest.php
index 088a872798bd..a95841f29962 100644
--- a/core/modules/contact/tests/src/Functional/Hal/MessageHalJsonAnonTest.php
+++ b/core/modules/contact/tests/src/Functional/Hal/MessageHalJsonAnonTest.php
@@ -19,6 +19,11 @@ class MessageHalJsonAnonTest extends MessageResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/contact/tests/src/Functional/Hal/MessageHalJsonBasicAuthTest.php b/core/modules/contact/tests/src/Functional/Hal/MessageHalJsonBasicAuthTest.php
index 363dbd7c87a8..4da136e45e9a 100644
--- a/core/modules/contact/tests/src/Functional/Hal/MessageHalJsonBasicAuthTest.php
+++ b/core/modules/contact/tests/src/Functional/Hal/MessageHalJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class MessageHalJsonBasicAuthTest extends MessageHalJsonAnonTest {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/contact/tests/src/Functional/Hal/MessageHalJsonCookieTest.php b/core/modules/contact/tests/src/Functional/Hal/MessageHalJsonCookieTest.php
index 0353cd2ea336..2d93a661c0fa 100644
--- a/core/modules/contact/tests/src/Functional/Hal/MessageHalJsonCookieTest.php
+++ b/core/modules/contact/tests/src/Functional/Hal/MessageHalJsonCookieTest.php
@@ -16,4 +16,9 @@ class MessageHalJsonCookieTest extends MessageHalJsonAnonTest {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/contact/tests/src/Functional/Rest/ContactFormJsonAnonTest.php b/core/modules/contact/tests/src/Functional/Rest/ContactFormJsonAnonTest.php
index fecbf68870ef..6f0eb3124590 100644
--- a/core/modules/contact/tests/src/Functional/Rest/ContactFormJsonAnonTest.php
+++ b/core/modules/contact/tests/src/Functional/Rest/ContactFormJsonAnonTest.php
@@ -21,4 +21,9 @@ class ContactFormJsonAnonTest extends ContactFormResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/contact/tests/src/Functional/Rest/ContactFormJsonBasicAuthTest.php b/core/modules/contact/tests/src/Functional/Rest/ContactFormJsonBasicAuthTest.php
index 8e92a91009b1..f5047081bdb5 100644
--- a/core/modules/contact/tests/src/Functional/Rest/ContactFormJsonBasicAuthTest.php
+++ b/core/modules/contact/tests/src/Functional/Rest/ContactFormJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class ContactFormJsonBasicAuthTest extends ContactFormResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/contact/tests/src/Functional/Rest/ContactFormJsonCookieTest.php b/core/modules/contact/tests/src/Functional/Rest/ContactFormJsonCookieTest.php
index 6ba666043a2e..076e370126a1 100644
--- a/core/modules/contact/tests/src/Functional/Rest/ContactFormJsonCookieTest.php
+++ b/core/modules/contact/tests/src/Functional/Rest/ContactFormJsonCookieTest.php
@@ -26,4 +26,9 @@ class ContactFormJsonCookieTest extends ContactFormResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/contact/tests/src/Functional/Rest/ContactFormXmlAnonTest.php b/core/modules/contact/tests/src/Functional/Rest/ContactFormXmlAnonTest.php
index 2931edda8d1a..f538af9192f2 100644
--- a/core/modules/contact/tests/src/Functional/Rest/ContactFormXmlAnonTest.php
+++ b/core/modules/contact/tests/src/Functional/Rest/ContactFormXmlAnonTest.php
@@ -23,4 +23,9 @@ class ContactFormXmlAnonTest extends ContactFormResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/contact/tests/src/Functional/Rest/ContactFormXmlBasicAuthTest.php b/core/modules/contact/tests/src/Functional/Rest/ContactFormXmlBasicAuthTest.php
index dfc4b6498a18..a2588c9f3b1d 100644
--- a/core/modules/contact/tests/src/Functional/Rest/ContactFormXmlBasicAuthTest.php
+++ b/core/modules/contact/tests/src/Functional/Rest/ContactFormXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class ContactFormXmlBasicAuthTest extends ContactFormResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/contact/tests/src/Functional/Rest/ContactFormXmlCookieTest.php b/core/modules/contact/tests/src/Functional/Rest/ContactFormXmlCookieTest.php
index cdcd2daa3e51..3dde171d8188 100644
--- a/core/modules/contact/tests/src/Functional/Rest/ContactFormXmlCookieTest.php
+++ b/core/modules/contact/tests/src/Functional/Rest/ContactFormXmlCookieTest.php
@@ -28,4 +28,9 @@ class ContactFormXmlCookieTest extends ContactFormResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/contact/tests/src/Functional/Rest/MessageJsonAnonTest.php b/core/modules/contact/tests/src/Functional/Rest/MessageJsonAnonTest.php
index a5b2954249ce..fbd0bee0916e 100644
--- a/core/modules/contact/tests/src/Functional/Rest/MessageJsonAnonTest.php
+++ b/core/modules/contact/tests/src/Functional/Rest/MessageJsonAnonTest.php
@@ -21,4 +21,9 @@ class MessageJsonAnonTest extends MessageResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/contact/tests/src/Functional/Rest/MessageJsonBasicAuthTest.php b/core/modules/contact/tests/src/Functional/Rest/MessageJsonBasicAuthTest.php
index f7f759ab9029..0d281630b078 100644
--- a/core/modules/contact/tests/src/Functional/Rest/MessageJsonBasicAuthTest.php
+++ b/core/modules/contact/tests/src/Functional/Rest/MessageJsonBasicAuthTest.php
@@ -26,6 +26,11 @@ class MessageJsonBasicAuthTest extends MessageResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/contact/tests/src/Functional/Rest/MessageJsonCookieTest.php b/core/modules/contact/tests/src/Functional/Rest/MessageJsonCookieTest.php
index 0444a5a06a93..e8fa8e8a3128 100644
--- a/core/modules/contact/tests/src/Functional/Rest/MessageJsonCookieTest.php
+++ b/core/modules/contact/tests/src/Functional/Rest/MessageJsonCookieTest.php
@@ -26,4 +26,9 @@ class MessageJsonCookieTest extends MessageResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/contact/tests/src/Functional/Rest/MessageXmlAnonTest.php b/core/modules/contact/tests/src/Functional/Rest/MessageXmlAnonTest.php
index 6b9b10de8a8d..51b327fd628f 100644
--- a/core/modules/contact/tests/src/Functional/Rest/MessageXmlAnonTest.php
+++ b/core/modules/contact/tests/src/Functional/Rest/MessageXmlAnonTest.php
@@ -23,4 +23,9 @@ class MessageXmlAnonTest extends MessageResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/contact/tests/src/Functional/Rest/MessageXmlBasicAuthTest.php b/core/modules/contact/tests/src/Functional/Rest/MessageXmlBasicAuthTest.php
index 152a94a86f28..64547a5a720a 100644
--- a/core/modules/contact/tests/src/Functional/Rest/MessageXmlBasicAuthTest.php
+++ b/core/modules/contact/tests/src/Functional/Rest/MessageXmlBasicAuthTest.php
@@ -28,6 +28,11 @@ class MessageXmlBasicAuthTest extends MessageResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/contact/tests/src/Functional/Rest/MessageXmlCookieTest.php b/core/modules/contact/tests/src/Functional/Rest/MessageXmlCookieTest.php
index ecdf0dba55c0..6bc53fec53a4 100644
--- a/core/modules/contact/tests/src/Functional/Rest/MessageXmlCookieTest.php
+++ b/core/modules/contact/tests/src/Functional/Rest/MessageXmlCookieTest.php
@@ -23,6 +23,11 @@ class MessageXmlCookieTest extends MessageResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/contact/tests/src/Functional/Views/ContactLinkTest.php b/core/modules/contact/tests/src/Functional/Views/ContactLinkTest.php
index 9eed21e068cf..f277e08bae75 100644
--- a/core/modules/contact/tests/src/Functional/Views/ContactLinkTest.php
+++ b/core/modules/contact/tests/src/Functional/Views/ContactLinkTest.php
@@ -29,6 +29,11 @@ class ContactLinkTest extends ViewTestBase {
    */
   public static $modules = ['contact_test_views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/content_moderation/tests/src/Functional/ContentModerationAdminPathEntityConverterLanguageTest.php b/core/modules/content_moderation/tests/src/Functional/ContentModerationAdminPathEntityConverterLanguageTest.php
index 5018361b58d2..01cb98a1ffa7 100644
--- a/core/modules/content_moderation/tests/src/Functional/ContentModerationAdminPathEntityConverterLanguageTest.php
+++ b/core/modules/content_moderation/tests/src/Functional/ContentModerationAdminPathEntityConverterLanguageTest.php
@@ -16,4 +16,9 @@ class ContentModerationAdminPathEntityConverterLanguageTest extends AdminPathEnt
    */
   public static $modules = ['language', 'language_test', 'content_moderation'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/content_moderation/tests/src/Functional/ContentModerationWorkflowTypeTest.php b/core/modules/content_moderation/tests/src/Functional/ContentModerationWorkflowTypeTest.php
index cbe5807a5fbe..144765934e78 100644
--- a/core/modules/content_moderation/tests/src/Functional/ContentModerationWorkflowTypeTest.php
+++ b/core/modules/content_moderation/tests/src/Functional/ContentModerationWorkflowTypeTest.php
@@ -22,6 +22,11 @@ class ContentModerationWorkflowTypeTest extends BrowserTestBase {
     'entity_test',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/content_moderation/tests/src/Functional/DefaultModerationStateTest.php b/core/modules/content_moderation/tests/src/Functional/DefaultModerationStateTest.php
index f5f6a5c004aa..9e1f9035c894 100644
--- a/core/modules/content_moderation/tests/src/Functional/DefaultModerationStateTest.php
+++ b/core/modules/content_moderation/tests/src/Functional/DefaultModerationStateTest.php
@@ -9,6 +9,11 @@
  */
 class DefaultModerationStateTest extends ModerationStateTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/content_moderation/tests/src/Functional/LayoutBuilderContentModerationIntegrationTest.php b/core/modules/content_moderation/tests/src/Functional/LayoutBuilderContentModerationIntegrationTest.php
index 3f61ea9eeb6e..c8a1493f9fde 100644
--- a/core/modules/content_moderation/tests/src/Functional/LayoutBuilderContentModerationIntegrationTest.php
+++ b/core/modules/content_moderation/tests/src/Functional/LayoutBuilderContentModerationIntegrationTest.php
@@ -26,6 +26,11 @@ class LayoutBuilderContentModerationIntegrationTest extends BrowserTestBase {
     'menu_ui',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/content_moderation/tests/src/Functional/ModeratedContentViewTest.php b/core/modules/content_moderation/tests/src/Functional/ModeratedContentViewTest.php
index b6ca37e94a55..0faf532f3c28 100644
--- a/core/modules/content_moderation/tests/src/Functional/ModeratedContentViewTest.php
+++ b/core/modules/content_moderation/tests/src/Functional/ModeratedContentViewTest.php
@@ -34,6 +34,11 @@ class ModeratedContentViewTest extends BrowserTestBase {
     'content_translation',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/content_moderation/tests/src/Functional/ModerationActionsTest.php b/core/modules/content_moderation/tests/src/Functional/ModerationActionsTest.php
index 2df82eb5d56b..267e9a8df54d 100644
--- a/core/modules/content_moderation/tests/src/Functional/ModerationActionsTest.php
+++ b/core/modules/content_moderation/tests/src/Functional/ModerationActionsTest.php
@@ -28,6 +28,11 @@ class ModerationActionsTest extends BrowserTestBase {
     'views',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/content_moderation/tests/src/Functional/ModerationContentTranslationTest.php b/core/modules/content_moderation/tests/src/Functional/ModerationContentTranslationTest.php
index 4afa97de6f4c..a36d23af00eb 100644
--- a/core/modules/content_moderation/tests/src/Functional/ModerationContentTranslationTest.php
+++ b/core/modules/content_moderation/tests/src/Functional/ModerationContentTranslationTest.php
@@ -32,6 +32,11 @@ class ModerationContentTranslationTest extends BrowserTestBase {
     'content_translation',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/content_moderation/tests/src/Functional/ModerationFormTest.php b/core/modules/content_moderation/tests/src/Functional/ModerationFormTest.php
index 679885c05900..4774f284b001 100644
--- a/core/modules/content_moderation/tests/src/Functional/ModerationFormTest.php
+++ b/core/modules/content_moderation/tests/src/Functional/ModerationFormTest.php
@@ -24,6 +24,11 @@ class ModerationFormTest extends ModerationStateTestBase {
     'content_translation',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/content_moderation/tests/src/Functional/ModerationLocaleTest.php b/core/modules/content_moderation/tests/src/Functional/ModerationLocaleTest.php
index 1bdbb7e46110..e61ab2da69c6 100644
--- a/core/modules/content_moderation/tests/src/Functional/ModerationLocaleTest.php
+++ b/core/modules/content_moderation/tests/src/Functional/ModerationLocaleTest.php
@@ -23,6 +23,11 @@ class ModerationLocaleTest extends ModerationStateTestBase {
     'content_translation',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/content_moderation/tests/src/Functional/ModerationRevisionRevertTest.php b/core/modules/content_moderation/tests/src/Functional/ModerationRevisionRevertTest.php
index 6e54d682ff6a..d7e9f13fc08e 100644
--- a/core/modules/content_moderation/tests/src/Functional/ModerationRevisionRevertTest.php
+++ b/core/modules/content_moderation/tests/src/Functional/ModerationRevisionRevertTest.php
@@ -26,6 +26,11 @@ class ModerationRevisionRevertTest extends BrowserTestBase {
     'node',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/content_moderation/tests/src/Functional/ModerationStateAccessTest.php b/core/modules/content_moderation/tests/src/Functional/ModerationStateAccessTest.php
index 09d5c8db64f2..51b24daf4e80 100644
--- a/core/modules/content_moderation/tests/src/Functional/ModerationStateAccessTest.php
+++ b/core/modules/content_moderation/tests/src/Functional/ModerationStateAccessTest.php
@@ -24,6 +24,11 @@ class ModerationStateAccessTest extends BrowserTestBase {
     'node',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/content_moderation/tests/src/Functional/ModerationStateBlockTest.php b/core/modules/content_moderation/tests/src/Functional/ModerationStateBlockTest.php
index 8b02848a30c2..06bd9a9c31e4 100644
--- a/core/modules/content_moderation/tests/src/Functional/ModerationStateBlockTest.php
+++ b/core/modules/content_moderation/tests/src/Functional/ModerationStateBlockTest.php
@@ -12,6 +12,11 @@
  */
 class ModerationStateBlockTest extends ModerationStateTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/content_moderation/tests/src/Functional/ModerationStateNodeTest.php b/core/modules/content_moderation/tests/src/Functional/ModerationStateNodeTest.php
index 8fd580896bf0..d04c42c84330 100644
--- a/core/modules/content_moderation/tests/src/Functional/ModerationStateNodeTest.php
+++ b/core/modules/content_moderation/tests/src/Functional/ModerationStateNodeTest.php
@@ -12,6 +12,11 @@
  */
 class ModerationStateNodeTest extends ModerationStateTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/content_moderation/tests/src/Functional/ModerationStateNodeTypeTest.php b/core/modules/content_moderation/tests/src/Functional/ModerationStateNodeTypeTest.php
index a0a5fe01f8d5..476642f0ad91 100644
--- a/core/modules/content_moderation/tests/src/Functional/ModerationStateNodeTypeTest.php
+++ b/core/modules/content_moderation/tests/src/Functional/ModerationStateNodeTypeTest.php
@@ -9,6 +9,11 @@
  */
 class ModerationStateNodeTypeTest extends ModerationStateTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A node type without moderation state disabled.
    *
diff --git a/core/modules/content_moderation/tests/src/Functional/NodeAccessTest.php b/core/modules/content_moderation/tests/src/Functional/NodeAccessTest.php
index 76e9d97608c4..5bee9bcb1713 100644
--- a/core/modules/content_moderation/tests/src/Functional/NodeAccessTest.php
+++ b/core/modules/content_moderation/tests/src/Functional/NodeAccessTest.php
@@ -24,6 +24,11 @@ class NodeAccessTest extends ModerationStateTestBase {
     'node_access_test',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Permissions to grant admin user.
    *
diff --git a/core/modules/content_moderation/tests/src/Functional/ViewsModerationStateFilterTest.php b/core/modules/content_moderation/tests/src/Functional/ViewsModerationStateFilterTest.php
index e7b1d35b05a0..9598e1bd081e 100644
--- a/core/modules/content_moderation/tests/src/Functional/ViewsModerationStateFilterTest.php
+++ b/core/modules/content_moderation/tests/src/Functional/ViewsModerationStateFilterTest.php
@@ -34,6 +34,11 @@ class ViewsModerationStateFilterTest extends ViewTestBase {
     'views_ui',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/content_moderation/tests/src/Functional/WorkspaceContentModerationIntegrationTest.php b/core/modules/content_moderation/tests/src/Functional/WorkspaceContentModerationIntegrationTest.php
index 2227c2dac50c..e2430e22adcd 100644
--- a/core/modules/content_moderation/tests/src/Functional/WorkspaceContentModerationIntegrationTest.php
+++ b/core/modules/content_moderation/tests/src/Functional/WorkspaceContentModerationIntegrationTest.php
@@ -20,6 +20,11 @@ class WorkspaceContentModerationIntegrationTest extends ModerationStateTestBase
    */
   public static $modules = ['node', 'workspaces'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/content_translation/tests/src/Functional/ContentTestTranslationUITest.php b/core/modules/content_translation/tests/src/Functional/ContentTestTranslationUITest.php
index 0b1de0b204f4..1480c41dc6dc 100644
--- a/core/modules/content_translation/tests/src/Functional/ContentTestTranslationUITest.php
+++ b/core/modules/content_translation/tests/src/Functional/ContentTestTranslationUITest.php
@@ -21,6 +21,11 @@ class ContentTestTranslationUITest extends ContentTranslationUITestBase {
    */
   public static $modules = ['language', 'content_translation', 'entity_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/content_translation/tests/src/Functional/ContentTranslationContextualLinksTest.php b/core/modules/content_translation/tests/src/Functional/ContentTranslationContextualLinksTest.php
index 8042d9100707..e2a945b011d0 100644
--- a/core/modules/content_translation/tests/src/Functional/ContentTranslationContextualLinksTest.php
+++ b/core/modules/content_translation/tests/src/Functional/ContentTranslationContextualLinksTest.php
@@ -21,6 +21,11 @@ class ContentTranslationContextualLinksTest extends BrowserTestBase {
    */
   protected $bundle;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The content type being tested.
    *
diff --git a/core/modules/content_translation/tests/src/Functional/ContentTranslationDisableSettingTest.php b/core/modules/content_translation/tests/src/Functional/ContentTranslationDisableSettingTest.php
index 6dffed7444b6..5b56f880c7d7 100644
--- a/core/modules/content_translation/tests/src/Functional/ContentTranslationDisableSettingTest.php
+++ b/core/modules/content_translation/tests/src/Functional/ContentTranslationDisableSettingTest.php
@@ -20,6 +20,11 @@ class ContentTranslationDisableSettingTest extends BrowserTestBase {
     'language',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that entity schemas are up-to-date after enabling translation.
    */
diff --git a/core/modules/content_translation/tests/src/Functional/ContentTranslationEnableTest.php b/core/modules/content_translation/tests/src/Functional/ContentTranslationEnableTest.php
index a3cc4e99466c..7ae73a8fd73d 100644
--- a/core/modules/content_translation/tests/src/Functional/ContentTranslationEnableTest.php
+++ b/core/modules/content_translation/tests/src/Functional/ContentTranslationEnableTest.php
@@ -16,6 +16,11 @@ class ContentTranslationEnableTest extends BrowserTestBase {
    */
   public static $modules = ['entity_test', 'menu_link_content', 'node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that entity schemas are up-to-date after enabling translation.
    */
diff --git a/core/modules/content_translation/tests/src/Functional/ContentTranslationEntityBundleUITest.php b/core/modules/content_translation/tests/src/Functional/ContentTranslationEntityBundleUITest.php
index 163b5e8ff31e..dfd291bd858c 100644
--- a/core/modules/content_translation/tests/src/Functional/ContentTranslationEntityBundleUITest.php
+++ b/core/modules/content_translation/tests/src/Functional/ContentTranslationEntityBundleUITest.php
@@ -13,6 +13,11 @@ class ContentTranslationEntityBundleUITest extends BrowserTestBase {
 
   public static $modules = ['language', 'content_translation', 'node', 'comment', 'field_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     $user = $this->drupalCreateUser(['access administration pages', 'administer languages', 'administer content translation', 'administer content types']);
diff --git a/core/modules/content_translation/tests/src/Functional/ContentTranslationLanguageChangeTest.php b/core/modules/content_translation/tests/src/Functional/ContentTranslationLanguageChangeTest.php
index 1bf836aaca87..b72af04df81e 100644
--- a/core/modules/content_translation/tests/src/Functional/ContentTranslationLanguageChangeTest.php
+++ b/core/modules/content_translation/tests/src/Functional/ContentTranslationLanguageChangeTest.php
@@ -24,6 +24,11 @@ class ContentTranslationLanguageChangeTest extends NodeTestBase {
    */
   public static $modules = ['language', 'content_translation', 'content_translation_test', 'node', 'block', 'field_ui', 'image'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/content_translation/tests/src/Functional/ContentTranslationLinkTagTest.php b/core/modules/content_translation/tests/src/Functional/ContentTranslationLinkTagTest.php
index 8ea652e954d3..2e77e70cb6e1 100644
--- a/core/modules/content_translation/tests/src/Functional/ContentTranslationLinkTagTest.php
+++ b/core/modules/content_translation/tests/src/Functional/ContentTranslationLinkTagTest.php
@@ -19,6 +19,11 @@ class ContentTranslationLinkTagTest extends BrowserTestBase {
    */
   public static $modules = ['entity_test', 'content_translation', 'content_translation_test', 'language'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The added languages.
    *
diff --git a/core/modules/content_translation/tests/src/Functional/ContentTranslationOperationsTest.php b/core/modules/content_translation/tests/src/Functional/ContentTranslationOperationsTest.php
index 8486ac529ff0..d2e4ba022451 100644
--- a/core/modules/content_translation/tests/src/Functional/ContentTranslationOperationsTest.php
+++ b/core/modules/content_translation/tests/src/Functional/ContentTranslationOperationsTest.php
@@ -20,6 +20,11 @@ class ContentTranslationOperationsTest extends NodeTestBase {
    */
   protected $baseUser1;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A base user.
    *
diff --git a/core/modules/content_translation/tests/src/Functional/ContentTranslationOutdatedRevisionTranslationTest.php b/core/modules/content_translation/tests/src/Functional/ContentTranslationOutdatedRevisionTranslationTest.php
index d37f5d8ec4a9..f91d3fd9b1d1 100644
--- a/core/modules/content_translation/tests/src/Functional/ContentTranslationOutdatedRevisionTranslationTest.php
+++ b/core/modules/content_translation/tests/src/Functional/ContentTranslationOutdatedRevisionTranslationTest.php
@@ -12,6 +12,11 @@
  */
 class ContentTranslationOutdatedRevisionTranslationTest extends ContentTranslationPendingRevisionTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/content_translation/tests/src/Functional/ContentTranslationRevisionTranslationDeletionTest.php b/core/modules/content_translation/tests/src/Functional/ContentTranslationRevisionTranslationDeletionTest.php
index 842d7deda8c4..dd9c04e6ca4d 100644
--- a/core/modules/content_translation/tests/src/Functional/ContentTranslationRevisionTranslationDeletionTest.php
+++ b/core/modules/content_translation/tests/src/Functional/ContentTranslationRevisionTranslationDeletionTest.php
@@ -12,6 +12,11 @@
  */
 class ContentTranslationRevisionTranslationDeletionTest extends ContentTranslationPendingRevisionTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/content_translation/tests/src/Functional/ContentTranslationSettingsTest.php b/core/modules/content_translation/tests/src/Functional/ContentTranslationSettingsTest.php
index 8b6565a6c517..4708fe8146cc 100644
--- a/core/modules/content_translation/tests/src/Functional/ContentTranslationSettingsTest.php
+++ b/core/modules/content_translation/tests/src/Functional/ContentTranslationSettingsTest.php
@@ -27,6 +27,11 @@ class ContentTranslationSettingsTest extends BrowserTestBase {
    */
   public static $modules = ['language', 'content_translation', 'node', 'comment', 'field_ui', 'entity_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/content_translation/tests/src/Functional/ContentTranslationSyncImageTest.php b/core/modules/content_translation/tests/src/Functional/ContentTranslationSyncImageTest.php
index cc5f5c0e70c5..899d1ada68f3 100644
--- a/core/modules/content_translation/tests/src/Functional/ContentTranslationSyncImageTest.php
+++ b/core/modules/content_translation/tests/src/Functional/ContentTranslationSyncImageTest.php
@@ -20,6 +20,11 @@ class ContentTranslationSyncImageTest extends ContentTranslationTestBase {
     getTestFiles as drupalGetTestFiles;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The cardinality of the image field.
    *
diff --git a/core/modules/content_translation/tests/src/Functional/ContentTranslationUISkipTest.php b/core/modules/content_translation/tests/src/Functional/ContentTranslationUISkipTest.php
index 97d0b00f5da6..7f3582d207c2 100644
--- a/core/modules/content_translation/tests/src/Functional/ContentTranslationUISkipTest.php
+++ b/core/modules/content_translation/tests/src/Functional/ContentTranslationUISkipTest.php
@@ -18,6 +18,11 @@ class ContentTranslationUISkipTest extends BrowserTestBase {
    */
   public static $modules = ['content_translation_test', 'user', 'node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the content_translation_ui_skip key functionality.
    */
diff --git a/core/modules/content_translation/tests/src/Functional/ContentTranslationUntranslatableFieldsTest.php b/core/modules/content_translation/tests/src/Functional/ContentTranslationUntranslatableFieldsTest.php
index 3d7acfd6d803..6623a3504439 100644
--- a/core/modules/content_translation/tests/src/Functional/ContentTranslationUntranslatableFieldsTest.php
+++ b/core/modules/content_translation/tests/src/Functional/ContentTranslationUntranslatableFieldsTest.php
@@ -19,6 +19,11 @@ class ContentTranslationUntranslatableFieldsTest extends ContentTranslationPendi
    */
   public static $modules = ['field_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/content_translation/tests/src/Functional/ContentTranslationWorkflowsTest.php b/core/modules/content_translation/tests/src/Functional/ContentTranslationWorkflowsTest.php
index 2407d4f44113..2efc272143cf 100644
--- a/core/modules/content_translation/tests/src/Functional/ContentTranslationWorkflowsTest.php
+++ b/core/modules/content_translation/tests/src/Functional/ContentTranslationWorkflowsTest.php
@@ -31,6 +31,11 @@ class ContentTranslationWorkflowsTest extends ContentTranslationTestBase {
    */
   public static $modules = ['language', 'content_translation', 'entity_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     $this->setupEntity();
diff --git a/core/modules/content_translation/tests/src/Functional/Views/ContentTranslationViewsUITest.php b/core/modules/content_translation/tests/src/Functional/Views/ContentTranslationViewsUITest.php
index 4b4d53a484d8..351ff78de724 100644
--- a/core/modules/content_translation/tests/src/Functional/Views/ContentTranslationViewsUITest.php
+++ b/core/modules/content_translation/tests/src/Functional/Views/ContentTranslationViewsUITest.php
@@ -25,6 +25,11 @@ class ContentTranslationViewsUITest extends UITestBase {
    */
   public static $modules = ['content_translation'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the views UI.
    */
diff --git a/core/modules/content_translation/tests/src/Functional/Views/TranslationLinkTest.php b/core/modules/content_translation/tests/src/Functional/Views/TranslationLinkTest.php
index d2e9e0d0cbed..6370ca8391ff 100644
--- a/core/modules/content_translation/tests/src/Functional/Views/TranslationLinkTest.php
+++ b/core/modules/content_translation/tests/src/Functional/Views/TranslationLinkTest.php
@@ -29,6 +29,11 @@ class TranslationLinkTest extends ContentTranslationTestBase {
    */
   public static $modules = ['content_translation_test_views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     // @todo Use entity_type once it is has multilingual Views integration.
     $this->entityTypeId = 'user';
diff --git a/core/modules/content_translation/tests/src/FunctionalJavascript/ContentTranslationContextualLinksTest.php b/core/modules/content_translation/tests/src/FunctionalJavascript/ContentTranslationContextualLinksTest.php
index 156b10d97ff9..4f8a1b557752 100644
--- a/core/modules/content_translation/tests/src/FunctionalJavascript/ContentTranslationContextualLinksTest.php
+++ b/core/modules/content_translation/tests/src/FunctionalJavascript/ContentTranslationContextualLinksTest.php
@@ -24,6 +24,11 @@ class ContentTranslationContextualLinksTest extends WebDriverTestBase {
    */
   public static $modules = ['content_translation', 'contextual', 'node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/contextual/tests/src/Functional/ContextualDynamicContextTest.php b/core/modules/contextual/tests/src/Functional/ContextualDynamicContextTest.php
index 74a6d504e80a..4f0ab275ff52 100644
--- a/core/modules/contextual/tests/src/Functional/ContextualDynamicContextTest.php
+++ b/core/modules/contextual/tests/src/Functional/ContextualDynamicContextTest.php
@@ -17,6 +17,11 @@
  */
 class ContextualDynamicContextTest extends BrowserTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * A user with permission to access contextual links and edit content.
    *
diff --git a/core/modules/contextual/tests/src/FunctionalJavascript/ContextualLinksTest.php b/core/modules/contextual/tests/src/FunctionalJavascript/ContextualLinksTest.php
index 29d2ec7be5b8..74d733e162c1 100644
--- a/core/modules/contextual/tests/src/FunctionalJavascript/ContextualLinksTest.php
+++ b/core/modules/contextual/tests/src/FunctionalJavascript/ContextualLinksTest.php
@@ -19,6 +19,11 @@ class ContextualLinksTest extends WebDriverTestBase {
    */
   public static $modules = ['block', 'contextual'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/contextual/tests/src/FunctionalJavascript/EditModeTest.php b/core/modules/contextual/tests/src/FunctionalJavascript/EditModeTest.php
index 4a00a7efc491..0133bca215ed 100644
--- a/core/modules/contextual/tests/src/FunctionalJavascript/EditModeTest.php
+++ b/core/modules/contextual/tests/src/FunctionalJavascript/EditModeTest.php
@@ -29,6 +29,11 @@ class EditModeTest extends WebDriverTestBase {
     'contextual',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/datetime/tests/src/Functional/DateFilterTest.php b/core/modules/datetime/tests/src/Functional/DateFilterTest.php
index 37018d8341de..0272bb25e1a6 100644
--- a/core/modules/datetime/tests/src/Functional/DateFilterTest.php
+++ b/core/modules/datetime/tests/src/Functional/DateFilterTest.php
@@ -42,6 +42,11 @@ class DateFilterTest extends ViewTestBase {
     'views_ui',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/datetime/tests/src/Functional/DateTimeFieldTest.php b/core/modules/datetime/tests/src/Functional/DateTimeFieldTest.php
index 1ffa0e865b80..fd55a918f318 100644
--- a/core/modules/datetime/tests/src/Functional/DateTimeFieldTest.php
+++ b/core/modules/datetime/tests/src/Functional/DateTimeFieldTest.php
@@ -25,6 +25,11 @@ class DateTimeFieldTest extends DateTestBase {
    */
   protected $defaultSettings = ['timezone_override' => ''];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/datetime/tests/src/Functional/DateTimeTimeAgoFormatterTest.php b/core/modules/datetime/tests/src/Functional/DateTimeTimeAgoFormatterTest.php
index d143413cbbf4..2d777d646496 100644
--- a/core/modules/datetime/tests/src/Functional/DateTimeTimeAgoFormatterTest.php
+++ b/core/modules/datetime/tests/src/Functional/DateTimeTimeAgoFormatterTest.php
@@ -41,6 +41,11 @@ class DateTimeTimeAgoFormatterTest extends BrowserTestBase {
    */
   public static $modules = ['datetime', 'entity_test', 'field_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/datetime/tests/src/Functional/EntityResource/EntityTest/EntityTestDateonlyTest.php b/core/modules/datetime/tests/src/Functional/EntityResource/EntityTest/EntityTestDateonlyTest.php
index e8c71ef0ccf3..9d00406d5fd9 100644
--- a/core/modules/datetime/tests/src/Functional/EntityResource/EntityTest/EntityTestDateonlyTest.php
+++ b/core/modules/datetime/tests/src/Functional/EntityResource/EntityTest/EntityTestDateonlyTest.php
@@ -27,6 +27,11 @@ class EntityTestDateonlyTest extends EntityTestResourceTestBase {
    */
   protected static $dateString = '2017-03-01';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Datetime test field name.
    *
diff --git a/core/modules/datetime/tests/src/Functional/EntityResource/EntityTest/EntityTestDatetimeTest.php b/core/modules/datetime/tests/src/Functional/EntityResource/EntityTest/EntityTestDatetimeTest.php
index f5efce53f383..a2134650b4e1 100644
--- a/core/modules/datetime/tests/src/Functional/EntityResource/EntityTest/EntityTestDatetimeTest.php
+++ b/core/modules/datetime/tests/src/Functional/EntityResource/EntityTest/EntityTestDatetimeTest.php
@@ -27,6 +27,11 @@ class EntityTestDatetimeTest extends EntityTestResourceTestBase {
    */
   protected static $dateString = '2017-03-01T20:02:00';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Datetime test field name.
    *
diff --git a/core/modules/datetime/tests/src/Functional/Views/FilterDateTest.php b/core/modules/datetime/tests/src/Functional/Views/FilterDateTest.php
index 6c106497ae2d..213d422fe55f 100644
--- a/core/modules/datetime/tests/src/Functional/Views/FilterDateTest.php
+++ b/core/modules/datetime/tests/src/Functional/Views/FilterDateTest.php
@@ -26,6 +26,11 @@ class FilterDateTest extends BrowserTestBase {
    */
   protected $fieldName = 'field_date';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Nodes to test.
    *
diff --git a/core/modules/datetime_range/tests/src/Functional/DateRangeFieldTest.php b/core/modules/datetime_range/tests/src/Functional/DateRangeFieldTest.php
index 65faabf97fb6..cdf95cce14b8 100644
--- a/core/modules/datetime_range/tests/src/Functional/DateRangeFieldTest.php
+++ b/core/modules/datetime_range/tests/src/Functional/DateRangeFieldTest.php
@@ -27,6 +27,11 @@ class DateRangeFieldTest extends DateTestBase {
    */
   public static $modules = ['datetime_range'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * The default display settings to use for the formatters.
    *
diff --git a/core/modules/datetime_range/tests/src/Functional/EntityResource/EntityTest/EntityTestDateRangeTest.php b/core/modules/datetime_range/tests/src/Functional/EntityResource/EntityTest/EntityTestDateRangeTest.php
index e669a2237109..07c819d48f0b 100644
--- a/core/modules/datetime_range/tests/src/Functional/EntityResource/EntityTest/EntityTestDateRangeTest.php
+++ b/core/modules/datetime_range/tests/src/Functional/EntityResource/EntityTest/EntityTestDateRangeTest.php
@@ -39,6 +39,11 @@ class EntityTestDateRangeTest extends EntityTestResourceTestBase {
    */
   public static $modules = ['datetime_range', 'entity_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/dblog/tests/src/Functional/DbLogResourceTest.php b/core/modules/dblog/tests/src/Functional/DbLogResourceTest.php
index fc22d49182ea..5a45f63cc05c 100644
--- a/core/modules/dblog/tests/src/Functional/DbLogResourceTest.php
+++ b/core/modules/dblog/tests/src/Functional/DbLogResourceTest.php
@@ -17,6 +17,11 @@ class DbLogResourceTest extends ResourceTestBase {
 
   use CookieResourceTestTrait;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/dblog/tests/src/Functional/DbLogTest.php b/core/modules/dblog/tests/src/Functional/DbLogTest.php
index 87856ce4a874..ee08a2900120 100644
--- a/core/modules/dblog/tests/src/Functional/DbLogTest.php
+++ b/core/modules/dblog/tests/src/Functional/DbLogTest.php
@@ -28,6 +28,11 @@ class DbLogTest extends BrowserTestBase {
    */
   public static $modules = ['dblog', 'node', 'forum', 'help', 'block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * A user with some relevant administrative permissions.
    *
diff --git a/core/modules/dblog/tests/src/Functional/DbLogViewsTest.php b/core/modules/dblog/tests/src/Functional/DbLogViewsTest.php
index 6e525cdf6f9d..cbb86f8c54e0 100644
--- a/core/modules/dblog/tests/src/Functional/DbLogViewsTest.php
+++ b/core/modules/dblog/tests/src/Functional/DbLogViewsTest.php
@@ -21,6 +21,11 @@ class DbLogViewsTest extends DbLogTest {
    */
   public static $modules = ['dblog', 'node', 'forum', 'help', 'block', 'views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/dynamic_page_cache/tests/src/Functional/DynamicPageCacheIntegrationTest.php b/core/modules/dynamic_page_cache/tests/src/Functional/DynamicPageCacheIntegrationTest.php
index ffa8f4375f64..1574679c24c8 100644
--- a/core/modules/dynamic_page_cache/tests/src/Functional/DynamicPageCacheIntegrationTest.php
+++ b/core/modules/dynamic_page_cache/tests/src/Functional/DynamicPageCacheIntegrationTest.php
@@ -32,6 +32,11 @@ class DynamicPageCacheIntegrationTest extends BrowserTestBase {
    */
   protected static $modules = ['dynamic_page_cache_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/editor/tests/src/Functional/EditorAdminTest.php b/core/modules/editor/tests/src/Functional/EditorAdminTest.php
index 7995b6629b40..780fa3b145ef 100644
--- a/core/modules/editor/tests/src/Functional/EditorAdminTest.php
+++ b/core/modules/editor/tests/src/Functional/EditorAdminTest.php
@@ -22,6 +22,11 @@ class EditorAdminTest extends BrowserTestBase {
    */
   public static $modules = ['filter', 'editor'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with the 'administer filters' permission.
    *
diff --git a/core/modules/editor/tests/src/Functional/EditorDialogAccessTest.php b/core/modules/editor/tests/src/Functional/EditorDialogAccessTest.php
index 3a97b351b34d..46a41a6a7226 100644
--- a/core/modules/editor/tests/src/Functional/EditorDialogAccessTest.php
+++ b/core/modules/editor/tests/src/Functional/EditorDialogAccessTest.php
@@ -20,6 +20,11 @@ class EditorDialogAccessTest extends BrowserTestBase {
    */
   public static $modules = ['editor', 'filter', 'ckeditor'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test access to the editor image dialog.
    */
diff --git a/core/modules/editor/tests/src/Functional/EditorLoadingTest.php b/core/modules/editor/tests/src/Functional/EditorLoadingTest.php
index 36ab8e896cc2..d02c744b3d4e 100644
--- a/core/modules/editor/tests/src/Functional/EditorLoadingTest.php
+++ b/core/modules/editor/tests/src/Functional/EditorLoadingTest.php
@@ -22,6 +22,11 @@ class EditorLoadingTest extends BrowserTestBase {
    */
   public static $modules = ['filter', 'editor', 'editor_test', 'node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * An untrusted user, with access to the 'plain_text' format.
    *
diff --git a/core/modules/editor/tests/src/Functional/EditorPrivateFileReferenceFilterTest.php b/core/modules/editor/tests/src/Functional/EditorPrivateFileReferenceFilterTest.php
index 4880c85fc8e1..c99a53cb48df 100644
--- a/core/modules/editor/tests/src/Functional/EditorPrivateFileReferenceFilterTest.php
+++ b/core/modules/editor/tests/src/Functional/EditorPrivateFileReferenceFilterTest.php
@@ -33,6 +33,11 @@ class EditorPrivateFileReferenceFilterTest extends BrowserTestBase {
     'editor_private_test',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the editor file reference filter with private files.
    */
diff --git a/core/modules/editor/tests/src/Functional/EditorSecurityTest.php b/core/modules/editor/tests/src/Functional/EditorSecurityTest.php
index 2428f70d6ea7..c6bd6495b5f9 100644
--- a/core/modules/editor/tests/src/Functional/EditorSecurityTest.php
+++ b/core/modules/editor/tests/src/Functional/EditorSecurityTest.php
@@ -22,6 +22,11 @@ class EditorSecurityTest extends BrowserTestBase {
    */
   protected static $sampleContent = '<p style="color: red">Hello, Dumbo Octopus!</p><script>alert(0)</script><embed type="image/svg+xml" src="image.svg" />';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The secured sample content to use in most tests.
    *
diff --git a/core/modules/editor/tests/src/Functional/EditorUploadImageScaleTest.php b/core/modules/editor/tests/src/Functional/EditorUploadImageScaleTest.php
index 46f9a6e4589d..b7a88d809c5f 100644
--- a/core/modules/editor/tests/src/Functional/EditorUploadImageScaleTest.php
+++ b/core/modules/editor/tests/src/Functional/EditorUploadImageScaleTest.php
@@ -24,6 +24,11 @@ class EditorUploadImageScaleTest extends BrowserTestBase {
    */
   public static $modules = ['editor', 'editor_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with permission as administer for testing.
    *
diff --git a/core/modules/editor/tests/src/Functional/Hal/EditorHalJsonAnonTest.php b/core/modules/editor/tests/src/Functional/Hal/EditorHalJsonAnonTest.php
index 97d917d6dcaa..473e3c9255df 100644
--- a/core/modules/editor/tests/src/Functional/Hal/EditorHalJsonAnonTest.php
+++ b/core/modules/editor/tests/src/Functional/Hal/EditorHalJsonAnonTest.php
@@ -17,6 +17,11 @@ class EditorHalJsonAnonTest extends EditorResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/editor/tests/src/Functional/Hal/EditorHalJsonBasicAuthTest.php b/core/modules/editor/tests/src/Functional/Hal/EditorHalJsonBasicAuthTest.php
index 05f496bb6fa1..57042e58b450 100644
--- a/core/modules/editor/tests/src/Functional/Hal/EditorHalJsonBasicAuthTest.php
+++ b/core/modules/editor/tests/src/Functional/Hal/EditorHalJsonBasicAuthTest.php
@@ -17,6 +17,11 @@ class EditorHalJsonBasicAuthTest extends EditorResourceTestBase {
    */
   public static $modules = ['hal', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/editor/tests/src/Functional/Hal/EditorHalJsonCookieTest.php b/core/modules/editor/tests/src/Functional/Hal/EditorHalJsonCookieTest.php
index 4fe7ec988598..b2db5fb34ac7 100644
--- a/core/modules/editor/tests/src/Functional/Hal/EditorHalJsonCookieTest.php
+++ b/core/modules/editor/tests/src/Functional/Hal/EditorHalJsonCookieTest.php
@@ -17,6 +17,11 @@ class EditorHalJsonCookieTest extends EditorResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/editor/tests/src/Functional/QuickEditIntegrationLoadingTest.php b/core/modules/editor/tests/src/Functional/QuickEditIntegrationLoadingTest.php
index 396c30a8a6a5..56916776f63c 100644
--- a/core/modules/editor/tests/src/Functional/QuickEditIntegrationLoadingTest.php
+++ b/core/modules/editor/tests/src/Functional/QuickEditIntegrationLoadingTest.php
@@ -21,6 +21,11 @@ class QuickEditIntegrationLoadingTest extends BrowserTestBase {
    */
   public static $modules = ['quickedit', 'filter', 'node', 'editor'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * The basic permissions necessary to view content and use in-place editing.
    *
diff --git a/core/modules/editor/tests/src/Functional/Rest/EditorJsonAnonTest.php b/core/modules/editor/tests/src/Functional/Rest/EditorJsonAnonTest.php
index 3809f0aedd51..53bc36b8863f 100644
--- a/core/modules/editor/tests/src/Functional/Rest/EditorJsonAnonTest.php
+++ b/core/modules/editor/tests/src/Functional/Rest/EditorJsonAnonTest.php
@@ -21,4 +21,9 @@ class EditorJsonAnonTest extends EditorResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/editor/tests/src/Functional/Rest/EditorJsonBasicAuthTest.php b/core/modules/editor/tests/src/Functional/Rest/EditorJsonBasicAuthTest.php
index f0c301030a4f..3b39696a9637 100644
--- a/core/modules/editor/tests/src/Functional/Rest/EditorJsonBasicAuthTest.php
+++ b/core/modules/editor/tests/src/Functional/Rest/EditorJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class EditorJsonBasicAuthTest extends EditorResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/editor/tests/src/Functional/Rest/EditorJsonCookieTest.php b/core/modules/editor/tests/src/Functional/Rest/EditorJsonCookieTest.php
index 95f1024c67b9..b840c7a1029d 100644
--- a/core/modules/editor/tests/src/Functional/Rest/EditorJsonCookieTest.php
+++ b/core/modules/editor/tests/src/Functional/Rest/EditorJsonCookieTest.php
@@ -26,4 +26,9 @@ class EditorJsonCookieTest extends EditorResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/editor/tests/src/Functional/Rest/EditorXmlAnonTest.php b/core/modules/editor/tests/src/Functional/Rest/EditorXmlAnonTest.php
index d5be1f6deb7b..79129309c621 100644
--- a/core/modules/editor/tests/src/Functional/Rest/EditorXmlAnonTest.php
+++ b/core/modules/editor/tests/src/Functional/Rest/EditorXmlAnonTest.php
@@ -23,4 +23,9 @@ class EditorXmlAnonTest extends EditorResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/editor/tests/src/Functional/Rest/EditorXmlBasicAuthTest.php b/core/modules/editor/tests/src/Functional/Rest/EditorXmlBasicAuthTest.php
index acab40b9a470..5e5aa467f506 100644
--- a/core/modules/editor/tests/src/Functional/Rest/EditorXmlBasicAuthTest.php
+++ b/core/modules/editor/tests/src/Functional/Rest/EditorXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class EditorXmlBasicAuthTest extends EditorResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/editor/tests/src/Functional/Rest/EditorXmlCookieTest.php b/core/modules/editor/tests/src/Functional/Rest/EditorXmlCookieTest.php
index 8940095162de..fdafcaa9a4cf 100644
--- a/core/modules/editor/tests/src/Functional/Rest/EditorXmlCookieTest.php
+++ b/core/modules/editor/tests/src/Functional/Rest/EditorXmlCookieTest.php
@@ -28,4 +28,9 @@ class EditorXmlCookieTest extends EditorResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/editor/tests/src/FunctionalJavascript/EditorAdminTest.php b/core/modules/editor/tests/src/FunctionalJavascript/EditorAdminTest.php
index 6652bdaec5b4..d3cea9755251 100644
--- a/core/modules/editor/tests/src/FunctionalJavascript/EditorAdminTest.php
+++ b/core/modules/editor/tests/src/FunctionalJavascript/EditorAdminTest.php
@@ -23,6 +23,11 @@ class EditorAdminTest extends WebDriverTestBase {
     'ckeditor',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/field/tests/src/Functional/Boolean/BooleanFieldTest.php b/core/modules/field/tests/src/Functional/Boolean/BooleanFieldTest.php
index 5d85c654650e..4852229a1579 100644
--- a/core/modules/field/tests/src/Functional/Boolean/BooleanFieldTest.php
+++ b/core/modules/field/tests/src/Functional/Boolean/BooleanFieldTest.php
@@ -26,6 +26,11 @@ class BooleanFieldTest extends BrowserTestBase {
     'field_test_boolean_access_denied',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * A field to use in this test class.
    *
diff --git a/core/modules/field/tests/src/Functional/Boolean/BooleanFormatterSettingsTest.php b/core/modules/field/tests/src/Functional/Boolean/BooleanFormatterSettingsTest.php
index af92c3f7354d..532c3992961b 100644
--- a/core/modules/field/tests/src/Functional/Boolean/BooleanFormatterSettingsTest.php
+++ b/core/modules/field/tests/src/Functional/Boolean/BooleanFormatterSettingsTest.php
@@ -20,6 +20,11 @@ class BooleanFormatterSettingsTest extends BrowserTestBase {
    */
   public static $modules = ['field', 'field_ui', 'text', 'node', 'user'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The name of the entity bundle that is created in the test.
    *
diff --git a/core/modules/field/tests/src/Functional/Email/EmailFieldTest.php b/core/modules/field/tests/src/Functional/Email/EmailFieldTest.php
index 3fb80a85d463..c044ba3c1c5a 100644
--- a/core/modules/field/tests/src/Functional/Email/EmailFieldTest.php
+++ b/core/modules/field/tests/src/Functional/Email/EmailFieldTest.php
@@ -21,6 +21,11 @@ class EmailFieldTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'entity_test', 'field_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A field storage to use in this test class.
    *
diff --git a/core/modules/field/tests/src/Functional/EntityReference/EntityReferenceAdminTest.php b/core/modules/field/tests/src/Functional/EntityReference/EntityReferenceAdminTest.php
index 9d82101c0ad4..bdb755c1d18e 100644
--- a/core/modules/field/tests/src/Functional/EntityReference/EntityReferenceAdminTest.php
+++ b/core/modules/field/tests/src/Functional/EntityReference/EntityReferenceAdminTest.php
@@ -30,6 +30,11 @@ class EntityReferenceAdminTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'field_ui', 'path', 'taxonomy', 'block', 'views_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The name of the content type created for testing purposes.
    *
diff --git a/core/modules/field/tests/src/Functional/EntityReference/EntityReferenceAutoCreateTest.php b/core/modules/field/tests/src/Functional/EntityReference/EntityReferenceAutoCreateTest.php
index 9c7b9b46c309..0e5deb0324cd 100644
--- a/core/modules/field/tests/src/Functional/EntityReference/EntityReferenceAutoCreateTest.php
+++ b/core/modules/field/tests/src/Functional/EntityReference/EntityReferenceAutoCreateTest.php
@@ -21,6 +21,11 @@ class EntityReferenceAutoCreateTest extends BrowserTestBase {
 
   public static $modules = ['node', 'taxonomy'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The name of a content type that will reference $referencedType.
    *
diff --git a/core/modules/field/tests/src/Functional/EntityReference/EntityReferenceFieldDefaultValueTest.php b/core/modules/field/tests/src/Functional/EntityReference/EntityReferenceFieldDefaultValueTest.php
index 89d30eb27cb2..9f50ed63ba1d 100644
--- a/core/modules/field/tests/src/Functional/EntityReference/EntityReferenceFieldDefaultValueTest.php
+++ b/core/modules/field/tests/src/Functional/EntityReference/EntityReferenceFieldDefaultValueTest.php
@@ -24,6 +24,11 @@ class EntityReferenceFieldDefaultValueTest extends BrowserTestBase {
    */
   public static $modules = ['field_ui', 'node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with permission to administer content types, node fields, etc.
    *
diff --git a/core/modules/field/tests/src/Functional/EntityReference/EntityReferenceFieldTranslatedReferenceViewTest.php b/core/modules/field/tests/src/Functional/EntityReference/EntityReferenceFieldTranslatedReferenceViewTest.php
index f327d4cd42ea..79ba27170b6f 100644
--- a/core/modules/field/tests/src/Functional/EntityReference/EntityReferenceFieldTranslatedReferenceViewTest.php
+++ b/core/modules/field/tests/src/Functional/EntityReference/EntityReferenceFieldTranslatedReferenceViewTest.php
@@ -124,6 +124,11 @@ class EntityReferenceFieldTranslatedReferenceViewTest extends BrowserTestBase {
     'node',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/field/tests/src/Functional/EntityReference/EntityReferenceFileUploadTest.php b/core/modules/field/tests/src/Functional/EntityReference/EntityReferenceFileUploadTest.php
index 7892aa867179..11374c9dd721 100644
--- a/core/modules/field/tests/src/Functional/EntityReference/EntityReferenceFileUploadTest.php
+++ b/core/modules/field/tests/src/Functional/EntityReference/EntityReferenceFileUploadTest.php
@@ -19,6 +19,11 @@ class EntityReferenceFileUploadTest extends BrowserTestBase {
 
   public static $modules = ['entity_reference', 'node', 'file'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The name of a content type that will reference $referencedType.
    *
diff --git a/core/modules/field/tests/src/Functional/EntityReference/EntityReferenceIntegrationTest.php b/core/modules/field/tests/src/Functional/EntityReference/EntityReferenceIntegrationTest.php
index 9c67d043f77e..9cc161396ed1 100644
--- a/core/modules/field/tests/src/Functional/EntityReference/EntityReferenceIntegrationTest.php
+++ b/core/modules/field/tests/src/Functional/EntityReference/EntityReferenceIntegrationTest.php
@@ -47,6 +47,11 @@ class EntityReferenceIntegrationTest extends BrowserTestBase {
    */
   public static $modules = ['config_test', 'entity_test', 'field_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/field/tests/src/Functional/EntityReference/EntityReferenceXSSTest.php b/core/modules/field/tests/src/Functional/EntityReference/EntityReferenceXSSTest.php
index a1867c2589bc..15529854dded 100644
--- a/core/modules/field/tests/src/Functional/EntityReference/EntityReferenceXSSTest.php
+++ b/core/modules/field/tests/src/Functional/EntityReference/EntityReferenceXSSTest.php
@@ -23,6 +23,11 @@ class EntityReferenceXSSTest extends BrowserTestBase {
    */
   protected static $modules = ['node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests markup is escaped in the entity reference select and label formatter.
    */
diff --git a/core/modules/field/tests/src/Functional/EntityReference/Views/SelectionTest.php b/core/modules/field/tests/src/Functional/EntityReference/Views/SelectionTest.php
index 16a18d96c11a..da732f6ffb71 100644
--- a/core/modules/field/tests/src/Functional/EntityReference/Views/SelectionTest.php
+++ b/core/modules/field/tests/src/Functional/EntityReference/Views/SelectionTest.php
@@ -29,6 +29,11 @@ class SelectionTest extends BrowserTestBase {
     'entity_test',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * An array of node titles, keyed by content type and node ID.
    *
diff --git a/core/modules/field/tests/src/Functional/FieldAccessTest.php b/core/modules/field/tests/src/Functional/FieldAccessTest.php
index 55a2812abe61..6a91bd1ef00d 100644
--- a/core/modules/field/tests/src/Functional/FieldAccessTest.php
+++ b/core/modules/field/tests/src/Functional/FieldAccessTest.php
@@ -19,6 +19,11 @@ class FieldAccessTest extends FieldTestBase {
    */
   public static $modules = ['node', 'field_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Node entity to use in this test.
    *
diff --git a/core/modules/field/tests/src/Functional/FieldDefaultValueCallbackTest.php b/core/modules/field/tests/src/Functional/FieldDefaultValueCallbackTest.php
index 4a70e7171c7b..da28d7710ed5 100644
--- a/core/modules/field/tests/src/Functional/FieldDefaultValueCallbackTest.php
+++ b/core/modules/field/tests/src/Functional/FieldDefaultValueCallbackTest.php
@@ -20,6 +20,11 @@ class FieldDefaultValueCallbackTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'field_test', 'field_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The field name.
    *
diff --git a/core/modules/field/tests/src/Functional/FieldHelpTest.php b/core/modules/field/tests/src/Functional/FieldHelpTest.php
index 712edec99acf..d0c2bb777fdc 100644
--- a/core/modules/field/tests/src/Functional/FieldHelpTest.php
+++ b/core/modules/field/tests/src/Functional/FieldHelpTest.php
@@ -18,6 +18,11 @@ class FieldHelpTest extends BrowserTestBase {
    */
   public static $modules = ['field', 'help'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   // Tests field help implementation without optional core modules enabled.
   protected $profile = 'minimal';
 
diff --git a/core/modules/field/tests/src/Functional/FieldImportDeleteUninstallUiTest.php b/core/modules/field/tests/src/Functional/FieldImportDeleteUninstallUiTest.php
index 25a798b8b9ba..6641d691f9a9 100644
--- a/core/modules/field/tests/src/Functional/FieldImportDeleteUninstallUiTest.php
+++ b/core/modules/field/tests/src/Functional/FieldImportDeleteUninstallUiTest.php
@@ -24,6 +24,11 @@ class FieldImportDeleteUninstallUiTest extends FieldTestBase {
    */
   public static $modules = ['entity_test', 'telephone', 'config', 'filter', 'datetime'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/field/tests/src/Functional/FormTest.php b/core/modules/field/tests/src/Functional/FormTest.php
index 671f01ac50a3..b409456cf945 100644
--- a/core/modules/field/tests/src/Functional/FormTest.php
+++ b/core/modules/field/tests/src/Functional/FormTest.php
@@ -27,6 +27,11 @@ class FormTest extends FieldTestBase {
    */
   public static $modules = ['node', 'field_test', 'options', 'entity_test', 'locale'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * An array of values defining a field single.
    *
diff --git a/core/modules/field/tests/src/Functional/Hal/FieldConfigHalJsonAnonTest.php b/core/modules/field/tests/src/Functional/Hal/FieldConfigHalJsonAnonTest.php
index 2137336c18d5..b32f25e5bf2d 100644
--- a/core/modules/field/tests/src/Functional/Hal/FieldConfigHalJsonAnonTest.php
+++ b/core/modules/field/tests/src/Functional/Hal/FieldConfigHalJsonAnonTest.php
@@ -17,6 +17,11 @@ class FieldConfigHalJsonAnonTest extends FieldConfigResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/field/tests/src/Functional/Hal/FieldConfigHalJsonBasicAuthTest.php b/core/modules/field/tests/src/Functional/Hal/FieldConfigHalJsonBasicAuthTest.php
index 8a299a4c4932..ce8838c1f33b 100644
--- a/core/modules/field/tests/src/Functional/Hal/FieldConfigHalJsonBasicAuthTest.php
+++ b/core/modules/field/tests/src/Functional/Hal/FieldConfigHalJsonBasicAuthTest.php
@@ -17,6 +17,11 @@ class FieldConfigHalJsonBasicAuthTest extends FieldConfigResourceTestBase {
    */
   public static $modules = ['hal', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/field/tests/src/Functional/Hal/FieldConfigHalJsonCookieTest.php b/core/modules/field/tests/src/Functional/Hal/FieldConfigHalJsonCookieTest.php
index c9f5ce0dd97f..b482ab03186d 100644
--- a/core/modules/field/tests/src/Functional/Hal/FieldConfigHalJsonCookieTest.php
+++ b/core/modules/field/tests/src/Functional/Hal/FieldConfigHalJsonCookieTest.php
@@ -17,6 +17,11 @@ class FieldConfigHalJsonCookieTest extends FieldConfigResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/field/tests/src/Functional/Hal/FieldStorageConfigHalJsonAnonTest.php b/core/modules/field/tests/src/Functional/Hal/FieldStorageConfigHalJsonAnonTest.php
index 7e74390b3859..72bc55058e25 100644
--- a/core/modules/field/tests/src/Functional/Hal/FieldStorageConfigHalJsonAnonTest.php
+++ b/core/modules/field/tests/src/Functional/Hal/FieldStorageConfigHalJsonAnonTest.php
@@ -17,6 +17,11 @@ class FieldStorageConfigHalJsonAnonTest extends FieldStorageConfigResourceTestBa
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/field/tests/src/Functional/Hal/FieldStorageConfigHalJsonBasicAuthTest.php b/core/modules/field/tests/src/Functional/Hal/FieldStorageConfigHalJsonBasicAuthTest.php
index e3c2a3fb9c9a..498589412afe 100644
--- a/core/modules/field/tests/src/Functional/Hal/FieldStorageConfigHalJsonBasicAuthTest.php
+++ b/core/modules/field/tests/src/Functional/Hal/FieldStorageConfigHalJsonBasicAuthTest.php
@@ -17,6 +17,11 @@ class FieldStorageConfigHalJsonBasicAuthTest extends FieldStorageConfigResourceT
    */
   public static $modules = ['hal', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/field/tests/src/Functional/Hal/FieldStorageConfigHalJsonCookieTest.php b/core/modules/field/tests/src/Functional/Hal/FieldStorageConfigHalJsonCookieTest.php
index 51df45617dfd..313e6ba7e269 100644
--- a/core/modules/field/tests/src/Functional/Hal/FieldStorageConfigHalJsonCookieTest.php
+++ b/core/modules/field/tests/src/Functional/Hal/FieldStorageConfigHalJsonCookieTest.php
@@ -17,6 +17,11 @@ class FieldStorageConfigHalJsonCookieTest extends FieldStorageConfigResourceTest
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/field/tests/src/Functional/NestedFormTest.php b/core/modules/field/tests/src/Functional/NestedFormTest.php
index 6ae583ff858e..31af3d485663 100644
--- a/core/modules/field/tests/src/Functional/NestedFormTest.php
+++ b/core/modules/field/tests/src/Functional/NestedFormTest.php
@@ -20,6 +20,11 @@ class NestedFormTest extends FieldTestBase {
    */
   public static $modules = ['field_test', 'entity_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/field/tests/src/Functional/Number/NumberFieldTest.php b/core/modules/field/tests/src/Functional/Number/NumberFieldTest.php
index 347b72c41904..2df7f41a93b1 100644
--- a/core/modules/field/tests/src/Functional/Number/NumberFieldTest.php
+++ b/core/modules/field/tests/src/Functional/Number/NumberFieldTest.php
@@ -20,6 +20,11 @@ class NumberFieldTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'entity_test', 'field_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     $this->drupalLogin($this->drupalCreateUser([
diff --git a/core/modules/field/tests/src/Functional/Rest/FieldConfigJsonAnonTest.php b/core/modules/field/tests/src/Functional/Rest/FieldConfigJsonAnonTest.php
index d11e46caf6b8..7fa684d868d8 100644
--- a/core/modules/field/tests/src/Functional/Rest/FieldConfigJsonAnonTest.php
+++ b/core/modules/field/tests/src/Functional/Rest/FieldConfigJsonAnonTest.php
@@ -21,4 +21,9 @@ class FieldConfigJsonAnonTest extends FieldConfigResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/field/tests/src/Functional/Rest/FieldConfigJsonBasicAuthTest.php b/core/modules/field/tests/src/Functional/Rest/FieldConfigJsonBasicAuthTest.php
index d27354eac2b3..376c752ee0e6 100644
--- a/core/modules/field/tests/src/Functional/Rest/FieldConfigJsonBasicAuthTest.php
+++ b/core/modules/field/tests/src/Functional/Rest/FieldConfigJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class FieldConfigJsonBasicAuthTest extends FieldConfigResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/field/tests/src/Functional/Rest/FieldConfigJsonCookieTest.php b/core/modules/field/tests/src/Functional/Rest/FieldConfigJsonCookieTest.php
index 089bd8f29935..413fa93fcefd 100644
--- a/core/modules/field/tests/src/Functional/Rest/FieldConfigJsonCookieTest.php
+++ b/core/modules/field/tests/src/Functional/Rest/FieldConfigJsonCookieTest.php
@@ -26,4 +26,9 @@ class FieldConfigJsonCookieTest extends FieldConfigResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/field/tests/src/Functional/Rest/FieldConfigXmlAnonTest.php b/core/modules/field/tests/src/Functional/Rest/FieldConfigXmlAnonTest.php
index 8809e60e937f..306625ee7e00 100644
--- a/core/modules/field/tests/src/Functional/Rest/FieldConfigXmlAnonTest.php
+++ b/core/modules/field/tests/src/Functional/Rest/FieldConfigXmlAnonTest.php
@@ -23,4 +23,9 @@ class FieldConfigXmlAnonTest extends FieldConfigResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/field/tests/src/Functional/Rest/FieldConfigXmlBasicAuthTest.php b/core/modules/field/tests/src/Functional/Rest/FieldConfigXmlBasicAuthTest.php
index 109f2dc94ac7..13b42d3eab65 100644
--- a/core/modules/field/tests/src/Functional/Rest/FieldConfigXmlBasicAuthTest.php
+++ b/core/modules/field/tests/src/Functional/Rest/FieldConfigXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class FieldConfigXmlBasicAuthTest extends FieldConfigResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/field/tests/src/Functional/Rest/FieldConfigXmlCookieTest.php b/core/modules/field/tests/src/Functional/Rest/FieldConfigXmlCookieTest.php
index d8aebdd1c88e..77adb16fa582 100644
--- a/core/modules/field/tests/src/Functional/Rest/FieldConfigXmlCookieTest.php
+++ b/core/modules/field/tests/src/Functional/Rest/FieldConfigXmlCookieTest.php
@@ -28,4 +28,9 @@ class FieldConfigXmlCookieTest extends FieldConfigResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/field/tests/src/Functional/Rest/FieldStorageConfigJsonAnonTest.php b/core/modules/field/tests/src/Functional/Rest/FieldStorageConfigJsonAnonTest.php
index 5e58c2a933a2..311dd45011ed 100644
--- a/core/modules/field/tests/src/Functional/Rest/FieldStorageConfigJsonAnonTest.php
+++ b/core/modules/field/tests/src/Functional/Rest/FieldStorageConfigJsonAnonTest.php
@@ -21,4 +21,9 @@ class FieldStorageConfigJsonAnonTest extends FieldStorageConfigResourceTestBase
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/field/tests/src/Functional/Rest/FieldStorageConfigJsonBasicAuthTest.php b/core/modules/field/tests/src/Functional/Rest/FieldStorageConfigJsonBasicAuthTest.php
index 9aa875ab899e..5256b0620362 100644
--- a/core/modules/field/tests/src/Functional/Rest/FieldStorageConfigJsonBasicAuthTest.php
+++ b/core/modules/field/tests/src/Functional/Rest/FieldStorageConfigJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class FieldStorageConfigJsonBasicAuthTest extends FieldStorageConfigResourceTest
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/field/tests/src/Functional/Rest/FieldStorageConfigJsonCookieTest.php b/core/modules/field/tests/src/Functional/Rest/FieldStorageConfigJsonCookieTest.php
index fbcf42b1b948..c61d3eb2c5d0 100644
--- a/core/modules/field/tests/src/Functional/Rest/FieldStorageConfigJsonCookieTest.php
+++ b/core/modules/field/tests/src/Functional/Rest/FieldStorageConfigJsonCookieTest.php
@@ -26,4 +26,9 @@ class FieldStorageConfigJsonCookieTest extends FieldStorageConfigResourceTestBas
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/field/tests/src/Functional/Rest/FieldStorageConfigXmlAnonTest.php b/core/modules/field/tests/src/Functional/Rest/FieldStorageConfigXmlAnonTest.php
index 4af918b03f62..66f3fb040da7 100644
--- a/core/modules/field/tests/src/Functional/Rest/FieldStorageConfigXmlAnonTest.php
+++ b/core/modules/field/tests/src/Functional/Rest/FieldStorageConfigXmlAnonTest.php
@@ -23,4 +23,9 @@ class FieldStorageConfigXmlAnonTest extends FieldStorageConfigResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/field/tests/src/Functional/Rest/FieldStorageConfigXmlBasicAuthTest.php b/core/modules/field/tests/src/Functional/Rest/FieldStorageConfigXmlBasicAuthTest.php
index d6fe68f8e719..cea708147044 100644
--- a/core/modules/field/tests/src/Functional/Rest/FieldStorageConfigXmlBasicAuthTest.php
+++ b/core/modules/field/tests/src/Functional/Rest/FieldStorageConfigXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class FieldStorageConfigXmlBasicAuthTest extends FieldStorageConfigResourceTestB
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/field/tests/src/Functional/Rest/FieldStorageConfigXmlCookieTest.php b/core/modules/field/tests/src/Functional/Rest/FieldStorageConfigXmlCookieTest.php
index 6672a0df023f..38730662ea8c 100644
--- a/core/modules/field/tests/src/Functional/Rest/FieldStorageConfigXmlCookieTest.php
+++ b/core/modules/field/tests/src/Functional/Rest/FieldStorageConfigXmlCookieTest.php
@@ -28,4 +28,9 @@ class FieldStorageConfigXmlCookieTest extends FieldStorageConfigResourceTestBase
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/field/tests/src/Functional/String/StringFieldTest.php b/core/modules/field/tests/src/Functional/String/StringFieldTest.php
index 21273673913a..d12fd33819d2 100644
--- a/core/modules/field/tests/src/Functional/String/StringFieldTest.php
+++ b/core/modules/field/tests/src/Functional/String/StringFieldTest.php
@@ -22,6 +22,11 @@ class StringFieldTest extends BrowserTestBase {
    */
   public static $modules = ['entity_test', 'file'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user without any special permissions.
    *
diff --git a/core/modules/field/tests/src/Functional/TranslationWebTest.php b/core/modules/field/tests/src/Functional/TranslationWebTest.php
index 400044bb56f4..d15692e1ad66 100644
--- a/core/modules/field/tests/src/Functional/TranslationWebTest.php
+++ b/core/modules/field/tests/src/Functional/TranslationWebTest.php
@@ -21,6 +21,11 @@ class TranslationWebTest extends FieldTestBase {
    */
   public static $modules = ['language', 'field_test', 'entity_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The name of the field to use in this test.
    *
diff --git a/core/modules/field/tests/src/Functional/Views/FieldUITest.php b/core/modules/field/tests/src/Functional/Views/FieldUITest.php
index f43b30d66294..8d4feaa34178 100644
--- a/core/modules/field/tests/src/Functional/Views/FieldUITest.php
+++ b/core/modules/field/tests/src/Functional/Views/FieldUITest.php
@@ -28,6 +28,11 @@ class FieldUITest extends FieldTestBase {
    */
   public static $modules = ['views_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with the 'administer views' permission.
    *
diff --git a/core/modules/field/tests/src/Functional/reEnableModuleFieldTest.php b/core/modules/field/tests/src/Functional/reEnableModuleFieldTest.php
index 39fb2dc9b376..21b91e0ebb1b 100644
--- a/core/modules/field/tests/src/Functional/reEnableModuleFieldTest.php
+++ b/core/modules/field/tests/src/Functional/reEnableModuleFieldTest.php
@@ -29,6 +29,11 @@ class reEnableModuleFieldTest extends BrowserTestBase {
     'telephone',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/field/tests/src/FunctionalJavascript/Boolean/BooleanFormatterSettingsTest.php b/core/modules/field/tests/src/FunctionalJavascript/Boolean/BooleanFormatterSettingsTest.php
index b6224c0e20cd..9fedc222a88c 100644
--- a/core/modules/field/tests/src/FunctionalJavascript/Boolean/BooleanFormatterSettingsTest.php
+++ b/core/modules/field/tests/src/FunctionalJavascript/Boolean/BooleanFormatterSettingsTest.php
@@ -20,6 +20,11 @@ class BooleanFormatterSettingsTest extends WebDriverTestBase {
    */
   public static $modules = ['field', 'field_ui', 'text', 'node', 'user'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The name of the entity bundle that is created in the test.
    *
diff --git a/core/modules/field/tests/src/FunctionalJavascript/EntityReference/EntityReferenceAdminTest.php b/core/modules/field/tests/src/FunctionalJavascript/EntityReference/EntityReferenceAdminTest.php
index 7b6fabe488c7..170c103c05b9 100644
--- a/core/modules/field/tests/src/FunctionalJavascript/EntityReference/EntityReferenceAdminTest.php
+++ b/core/modules/field/tests/src/FunctionalJavascript/EntityReference/EntityReferenceAdminTest.php
@@ -27,6 +27,11 @@ class EntityReferenceAdminTest extends WebDriverTestBase {
    */
   public static $modules = ['node', 'field_ui', 'path', 'taxonomy', 'block', 'views_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The name of the content type created for testing purposes.
    *
diff --git a/core/modules/field/tests/src/FunctionalJavascript/FormJSAddMoreTest.php b/core/modules/field/tests/src/FunctionalJavascript/FormJSAddMoreTest.php
index 0561d7371199..d56a723caf89 100644
--- a/core/modules/field/tests/src/FunctionalJavascript/FormJSAddMoreTest.php
+++ b/core/modules/field/tests/src/FunctionalJavascript/FormJSAddMoreTest.php
@@ -20,6 +20,11 @@ class FormJSAddMoreTest extends WebDriverTestBase {
    */
   public static $modules = ['field_test', 'entity_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/field/tests/src/FunctionalJavascript/Number/NumberFieldTest.php b/core/modules/field/tests/src/FunctionalJavascript/Number/NumberFieldTest.php
index e649e72eeb14..cefa69e38f35 100644
--- a/core/modules/field/tests/src/FunctionalJavascript/Number/NumberFieldTest.php
+++ b/core/modules/field/tests/src/FunctionalJavascript/Number/NumberFieldTest.php
@@ -19,6 +19,11 @@ class NumberFieldTest extends WebDriverTestBase {
    */
   protected static $modules = ['node', 'entity_test', 'field_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/field_layout/tests/src/Functional/FieldLayoutTest.php b/core/modules/field_layout/tests/src/Functional/FieldLayoutTest.php
index 9bab0b54312c..47458e458312 100644
--- a/core/modules/field_layout/tests/src/Functional/FieldLayoutTest.php
+++ b/core/modules/field_layout/tests/src/Functional/FieldLayoutTest.php
@@ -16,6 +16,11 @@ class FieldLayoutTest extends BrowserTestBase {
    */
   public static $modules = ['field_layout', 'field_ui', 'node', 'field_layout_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/field_layout/tests/src/FunctionalJavascript/FieldLayoutTest.php b/core/modules/field_layout/tests/src/FunctionalJavascript/FieldLayoutTest.php
index 8a36c8489f51..9114b93787a5 100644
--- a/core/modules/field_layout/tests/src/FunctionalJavascript/FieldLayoutTest.php
+++ b/core/modules/field_layout/tests/src/FunctionalJavascript/FieldLayoutTest.php
@@ -17,6 +17,11 @@ class FieldLayoutTest extends WebDriverTestBase {
    */
   public static $modules = ['field_layout', 'field_ui', 'field_layout_test', 'layout_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/field_ui/tests/src/Functional/EntityDisplayModeTest.php b/core/modules/field_ui/tests/src/Functional/EntityDisplayModeTest.php
index 953684193d3c..2a04bf258f06 100644
--- a/core/modules/field_ui/tests/src/Functional/EntityDisplayModeTest.php
+++ b/core/modules/field_ui/tests/src/Functional/EntityDisplayModeTest.php
@@ -21,6 +21,11 @@ class EntityDisplayModeTest extends BrowserTestBase {
    */
   public static $modules = ['block', 'entity_test', 'field_ui', 'node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/field_ui/tests/src/Functional/EntityDisplayTest.php b/core/modules/field_ui/tests/src/Functional/EntityDisplayTest.php
index c9cfc052ab50..d7b63558a358 100644
--- a/core/modules/field_ui/tests/src/Functional/EntityDisplayTest.php
+++ b/core/modules/field_ui/tests/src/Functional/EntityDisplayTest.php
@@ -16,6 +16,11 @@ class EntityDisplayTest extends BrowserTestBase {
    */
   public static $modules = ['field_ui', 'entity_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/field_ui/tests/src/Functional/FieldUIDeleteTest.php b/core/modules/field_ui/tests/src/Functional/FieldUIDeleteTest.php
index 5236905581e4..ef047f6d4755 100644
--- a/core/modules/field_ui/tests/src/Functional/FieldUIDeleteTest.php
+++ b/core/modules/field_ui/tests/src/Functional/FieldUIDeleteTest.php
@@ -25,6 +25,11 @@ class FieldUIDeleteTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'field_ui', 'field_test', 'block', 'field_test_views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test views to enable
    *
diff --git a/core/modules/field_ui/tests/src/Functional/FieldUIIndentationTest.php b/core/modules/field_ui/tests/src/Functional/FieldUIIndentationTest.php
index 1f66c9a77276..0eeff4bcbdc5 100644
--- a/core/modules/field_ui/tests/src/Functional/FieldUIIndentationTest.php
+++ b/core/modules/field_ui/tests/src/Functional/FieldUIIndentationTest.php
@@ -18,6 +18,11 @@ class FieldUIIndentationTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'field_ui', 'field_ui_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/field_ui/tests/src/Functional/FieldUIRouteTest.php b/core/modules/field_ui/tests/src/Functional/FieldUIRouteTest.php
index fe7a27011cac..7bbc546206ee 100644
--- a/core/modules/field_ui/tests/src/Functional/FieldUIRouteTest.php
+++ b/core/modules/field_ui/tests/src/Functional/FieldUIRouteTest.php
@@ -20,6 +20,11 @@ class FieldUIRouteTest extends BrowserTestBase {
    */
   public static $modules = ['block', 'entity_test', 'field_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/field_ui/tests/src/Functional/ManageDisplayTest.php b/core/modules/field_ui/tests/src/Functional/ManageDisplayTest.php
index aedb63e27d04..60ab7c03fdbc 100644
--- a/core/modules/field_ui/tests/src/Functional/ManageDisplayTest.php
+++ b/core/modules/field_ui/tests/src/Functional/ManageDisplayTest.php
@@ -27,6 +27,11 @@ class ManageDisplayTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'field_ui', 'taxonomy', 'search', 'field_test', 'field_third_party_test', 'block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/field_ui/tests/src/Functional/ManageFieldsFunctionalTest.php b/core/modules/field_ui/tests/src/Functional/ManageFieldsFunctionalTest.php
index bf86b7e98fc4..616bedd1b74c 100644
--- a/core/modules/field_ui/tests/src/Functional/ManageFieldsFunctionalTest.php
+++ b/core/modules/field_ui/tests/src/Functional/ManageFieldsFunctionalTest.php
@@ -29,6 +29,11 @@ class ManageFieldsFunctionalTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'field_ui', 'field_test', 'taxonomy', 'image', 'block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The ID of the custom content type created for testing.
    *
diff --git a/core/modules/field_ui/tests/src/Functional/ManageFieldsTest.php b/core/modules/field_ui/tests/src/Functional/ManageFieldsTest.php
index 1c21b069b4bc..c696e5878374 100644
--- a/core/modules/field_ui/tests/src/Functional/ManageFieldsTest.php
+++ b/core/modules/field_ui/tests/src/Functional/ManageFieldsTest.php
@@ -21,6 +21,11 @@ class ManageFieldsTest extends BrowserTestBase {
     'text',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/field_ui/tests/src/FunctionalJavascript/EntityDisplayTest.php b/core/modules/field_ui/tests/src/FunctionalJavascript/EntityDisplayTest.php
index 7909f0f0061c..22c1f1b2c70c 100644
--- a/core/modules/field_ui/tests/src/FunctionalJavascript/EntityDisplayTest.php
+++ b/core/modules/field_ui/tests/src/FunctionalJavascript/EntityDisplayTest.php
@@ -17,6 +17,11 @@ class EntityDisplayTest extends WebDriverTestBase {
    */
   public static $modules = ['field_ui', 'entity_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/field_ui/tests/src/FunctionalJavascript/ManageDisplayTest.php b/core/modules/field_ui/tests/src/FunctionalJavascript/ManageDisplayTest.php
index 404e6ed33e89..45fa8e818e9f 100644
--- a/core/modules/field_ui/tests/src/FunctionalJavascript/ManageDisplayTest.php
+++ b/core/modules/field_ui/tests/src/FunctionalJavascript/ManageDisplayTest.php
@@ -23,6 +23,11 @@ class ManageDisplayTest extends WebDriverTestBase {
     'block',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * @var string
    */
diff --git a/core/modules/file/tests/src/Functional/DownloadTest.php b/core/modules/file/tests/src/Functional/DownloadTest.php
index 68ef66c2110c..133729f4b560 100644
--- a/core/modules/file/tests/src/Functional/DownloadTest.php
+++ b/core/modules/file/tests/src/Functional/DownloadTest.php
@@ -11,6 +11,11 @@
  */
 class DownloadTest extends FileManagedTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     // Clear out any hook calls.
diff --git a/core/modules/file/tests/src/Functional/FileFieldAnonymousSubmissionTest.php b/core/modules/file/tests/src/Functional/FileFieldAnonymousSubmissionTest.php
index 70181dac808c..5e389e2b9793 100644
--- a/core/modules/file/tests/src/Functional/FileFieldAnonymousSubmissionTest.php
+++ b/core/modules/file/tests/src/Functional/FileFieldAnonymousSubmissionTest.php
@@ -13,6 +13,11 @@
  */
 class FileFieldAnonymousSubmissionTest extends FileFieldTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/file/tests/src/Functional/FileFieldDisplayTest.php b/core/modules/file/tests/src/Functional/FileFieldDisplayTest.php
index 2fa7f51e3ea6..922985cb4e31 100644
--- a/core/modules/file/tests/src/Functional/FileFieldDisplayTest.php
+++ b/core/modules/file/tests/src/Functional/FileFieldDisplayTest.php
@@ -14,6 +14,11 @@
  */
 class FileFieldDisplayTest extends FileFieldTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests normal formatter display on node display.
    */
diff --git a/core/modules/file/tests/src/Functional/FileFieldFormatterAccessTest.php b/core/modules/file/tests/src/Functional/FileFieldFormatterAccessTest.php
index 2337861978c7..4dc6aedf5dd2 100644
--- a/core/modules/file/tests/src/Functional/FileFieldFormatterAccessTest.php
+++ b/core/modules/file/tests/src/Functional/FileFieldFormatterAccessTest.php
@@ -15,6 +15,11 @@ class FileFieldFormatterAccessTest extends FileFieldTestBase {
    */
   public static $modules = ['node', 'file', 'field_ui', 'file_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the custom access handler is invoked.
    */
diff --git a/core/modules/file/tests/src/Functional/FileFieldPathTest.php b/core/modules/file/tests/src/Functional/FileFieldPathTest.php
index 5acc0d9eb42f..0a0fa79a573c 100644
--- a/core/modules/file/tests/src/Functional/FileFieldPathTest.php
+++ b/core/modules/file/tests/src/Functional/FileFieldPathTest.php
@@ -12,6 +12,11 @@
  */
 class FileFieldPathTest extends FileFieldTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the normal formatter display on node display.
    */
diff --git a/core/modules/file/tests/src/Functional/FileFieldRSSContentTest.php b/core/modules/file/tests/src/Functional/FileFieldRSSContentTest.php
index 57d2fd2363a4..73f94047a068 100644
--- a/core/modules/file/tests/src/Functional/FileFieldRSSContentTest.php
+++ b/core/modules/file/tests/src/Functional/FileFieldRSSContentTest.php
@@ -18,6 +18,11 @@ class FileFieldRSSContentTest extends FileFieldTestBase {
    */
   public static $modules = ['node', 'views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests RSS enclosure formatter display for RSS feeds.
    */
diff --git a/core/modules/file/tests/src/Functional/FileFieldRevisionTest.php b/core/modules/file/tests/src/Functional/FileFieldRevisionTest.php
index 3214c0b92d9b..39136b2f55ec 100644
--- a/core/modules/file/tests/src/Functional/FileFieldRevisionTest.php
+++ b/core/modules/file/tests/src/Functional/FileFieldRevisionTest.php
@@ -12,6 +12,11 @@
  */
 class FileFieldRevisionTest extends FileFieldTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests creating multiple revisions of a node and managing attached files.
    *
diff --git a/core/modules/file/tests/src/Functional/FileFieldValidateTest.php b/core/modules/file/tests/src/Functional/FileFieldValidateTest.php
index 5c7b5cfff1a3..5aa059af45fa 100644
--- a/core/modules/file/tests/src/Functional/FileFieldValidateTest.php
+++ b/core/modules/file/tests/src/Functional/FileFieldValidateTest.php
@@ -19,6 +19,11 @@ class FileFieldValidateTest extends FileFieldTestBase {
 
   use ExpectDeprecationTrait;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the required property on file fields.
    */
diff --git a/core/modules/file/tests/src/Functional/FileFieldWidgetTest.php b/core/modules/file/tests/src/Functional/FileFieldWidgetTest.php
index 781208a91f03..ff14143a650b 100644
--- a/core/modules/file/tests/src/Functional/FileFieldWidgetTest.php
+++ b/core/modules/file/tests/src/Functional/FileFieldWidgetTest.php
@@ -30,6 +30,11 @@ class FileFieldWidgetTest extends FileFieldTestBase {
    */
   protected static $modules = ['comment', 'block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/file/tests/src/Functional/FileListingTest.php b/core/modules/file/tests/src/Functional/FileListingTest.php
index 93f2dc8a0502..4feffa5d01fb 100644
--- a/core/modules/file/tests/src/Functional/FileListingTest.php
+++ b/core/modules/file/tests/src/Functional/FileListingTest.php
@@ -20,6 +20,11 @@ class FileListingTest extends FileFieldTestBase {
    */
   public static $modules = ['views', 'file', 'image', 'entity_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * An authenticated user.
    *
diff --git a/core/modules/file/tests/src/Functional/FileManagedFileElementTest.php b/core/modules/file/tests/src/Functional/FileManagedFileElementTest.php
index 2b448ba7dbfb..ac9350912c38 100644
--- a/core/modules/file/tests/src/Functional/FileManagedFileElementTest.php
+++ b/core/modules/file/tests/src/Functional/FileManagedFileElementTest.php
@@ -11,6 +11,11 @@
  */
 class FileManagedFileElementTest extends FileFieldTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the managed_file element type.
    */
diff --git a/core/modules/file/tests/src/Functional/FileOnTranslatedEntityTest.php b/core/modules/file/tests/src/Functional/FileOnTranslatedEntityTest.php
index 65aa802b929f..7bc1e0a808b5 100644
--- a/core/modules/file/tests/src/Functional/FileOnTranslatedEntityTest.php
+++ b/core/modules/file/tests/src/Functional/FileOnTranslatedEntityTest.php
@@ -16,6 +16,11 @@ class FileOnTranslatedEntityTest extends FileFieldTestBase {
    */
   public static $modules = ['language', 'content_translation'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The name of the file field used in the test.
    *
diff --git a/core/modules/file/tests/src/Functional/FilePrivateTest.php b/core/modules/file/tests/src/Functional/FilePrivateTest.php
index 4b699ef43693..1ac6d138ea83 100644
--- a/core/modules/file/tests/src/Functional/FilePrivateTest.php
+++ b/core/modules/file/tests/src/Functional/FilePrivateTest.php
@@ -22,6 +22,11 @@ class FilePrivateTest extends FileFieldTestBase {
    */
   public static $modules = ['node_access_test', 'field_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     node_access_test_add_field(NodeType::load('article'));
diff --git a/core/modules/file/tests/src/Functional/FileTokenReplaceTest.php b/core/modules/file/tests/src/Functional/FileTokenReplaceTest.php
index 14759e98569a..4b832ac26791 100644
--- a/core/modules/file/tests/src/Functional/FileTokenReplaceTest.php
+++ b/core/modules/file/tests/src/Functional/FileTokenReplaceTest.php
@@ -15,6 +15,11 @@
  */
 class FileTokenReplaceTest extends FileFieldTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Creates a file, then tests the tokens generated from it.
    */
diff --git a/core/modules/file/tests/src/Functional/FileUploadJsonBasicAuthTest.php b/core/modules/file/tests/src/Functional/FileUploadJsonBasicAuthTest.php
index cef59f83cf2e..49f50f6614a2 100644
--- a/core/modules/file/tests/src/Functional/FileUploadJsonBasicAuthTest.php
+++ b/core/modules/file/tests/src/Functional/FileUploadJsonBasicAuthTest.php
@@ -17,6 +17,11 @@ class FileUploadJsonBasicAuthTest extends FileUploadResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/file/tests/src/Functional/FileUploadJsonCookieTest.php b/core/modules/file/tests/src/Functional/FileUploadJsonCookieTest.php
index 8f7495a763b1..726b6fbffd3c 100644
--- a/core/modules/file/tests/src/Functional/FileUploadJsonCookieTest.php
+++ b/core/modules/file/tests/src/Functional/FileUploadJsonCookieTest.php
@@ -12,6 +12,11 @@ class FileUploadJsonCookieTest extends FileUploadResourceTestBase {
 
   use CookieResourceTestTrait;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/file/tests/src/Functional/Formatter/FileAudioFormatterTest.php b/core/modules/file/tests/src/Functional/Formatter/FileAudioFormatterTest.php
index 2de18a294d0e..4ec5bc3447ed 100644
--- a/core/modules/file/tests/src/Functional/Formatter/FileAudioFormatterTest.php
+++ b/core/modules/file/tests/src/Functional/Formatter/FileAudioFormatterTest.php
@@ -11,6 +11,11 @@
  */
 class FileAudioFormatterTest extends FileMediaFormatterTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * @covers ::viewElements
    *
diff --git a/core/modules/file/tests/src/Functional/Formatter/FileVideoFormatterTest.php b/core/modules/file/tests/src/Functional/Formatter/FileVideoFormatterTest.php
index 8517b3244d69..ec1ca79199fa 100644
--- a/core/modules/file/tests/src/Functional/Formatter/FileVideoFormatterTest.php
+++ b/core/modules/file/tests/src/Functional/Formatter/FileVideoFormatterTest.php
@@ -11,6 +11,11 @@
  */
 class FileVideoFormatterTest extends FileMediaFormatterTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * @covers ::viewElements
    *
diff --git a/core/modules/file/tests/src/Functional/Hal/FileHalJsonAnonTest.php b/core/modules/file/tests/src/Functional/Hal/FileHalJsonAnonTest.php
index 6a1310078caa..ca4fcf551afa 100644
--- a/core/modules/file/tests/src/Functional/Hal/FileHalJsonAnonTest.php
+++ b/core/modules/file/tests/src/Functional/Hal/FileHalJsonAnonTest.php
@@ -20,6 +20,11 @@ class FileHalJsonAnonTest extends FileResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/file/tests/src/Functional/Hal/FileHalJsonBasicAuthTest.php b/core/modules/file/tests/src/Functional/Hal/FileHalJsonBasicAuthTest.php
index 910107172821..5fbf7678eb78 100644
--- a/core/modules/file/tests/src/Functional/Hal/FileHalJsonBasicAuthTest.php
+++ b/core/modules/file/tests/src/Functional/Hal/FileHalJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class FileHalJsonBasicAuthTest extends FileHalJsonAnonTest {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/file/tests/src/Functional/Hal/FileHalJsonCookieTest.php b/core/modules/file/tests/src/Functional/Hal/FileHalJsonCookieTest.php
index 7069e9b964f5..47abaf3a3c01 100644
--- a/core/modules/file/tests/src/Functional/Hal/FileHalJsonCookieTest.php
+++ b/core/modules/file/tests/src/Functional/Hal/FileHalJsonCookieTest.php
@@ -16,4 +16,9 @@ class FileHalJsonCookieTest extends FileHalJsonAnonTest {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/file/tests/src/Functional/Hal/FileUploadHalJsonBasicAuthTest.php b/core/modules/file/tests/src/Functional/Hal/FileUploadHalJsonBasicAuthTest.php
index 647b85b9d65f..7cb3fb256b3e 100644
--- a/core/modules/file/tests/src/Functional/Hal/FileUploadHalJsonBasicAuthTest.php
+++ b/core/modules/file/tests/src/Functional/Hal/FileUploadHalJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class FileUploadHalJsonBasicAuthTest extends FileUploadHalJsonTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/file/tests/src/Functional/Hal/FileUploadHalJsonCookieTest.php b/core/modules/file/tests/src/Functional/Hal/FileUploadHalJsonCookieTest.php
index 510b6acfb976..b9937c09a512 100644
--- a/core/modules/file/tests/src/Functional/Hal/FileUploadHalJsonCookieTest.php
+++ b/core/modules/file/tests/src/Functional/Hal/FileUploadHalJsonCookieTest.php
@@ -16,4 +16,9 @@ class FileUploadHalJsonCookieTest extends FileUploadHalJsonTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/file/tests/src/Functional/MultipleFileUploadTest.php b/core/modules/file/tests/src/Functional/MultipleFileUploadTest.php
index 7ed5ccdcc108..8817a66d9c4c 100644
--- a/core/modules/file/tests/src/Functional/MultipleFileUploadTest.php
+++ b/core/modules/file/tests/src/Functional/MultipleFileUploadTest.php
@@ -16,6 +16,11 @@ class MultipleFileUploadTest extends BrowserTestBase {
    */
   public static $modules = ['file'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/file/tests/src/Functional/PrivateFileOnTranslatedEntityTest.php b/core/modules/file/tests/src/Functional/PrivateFileOnTranslatedEntityTest.php
index 44b2ee10c9c7..a838efef66fa 100644
--- a/core/modules/file/tests/src/Functional/PrivateFileOnTranslatedEntityTest.php
+++ b/core/modules/file/tests/src/Functional/PrivateFileOnTranslatedEntityTest.php
@@ -17,6 +17,11 @@ class PrivateFileOnTranslatedEntityTest extends FileFieldTestBase {
    */
   public static $modules = ['language', 'content_translation'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The name of the file field used in the test.
    *
diff --git a/core/modules/file/tests/src/Functional/RemoteFileSaveUploadTest.php b/core/modules/file/tests/src/Functional/RemoteFileSaveUploadTest.php
index e0e4be4b3cc2..91a909fd8c88 100644
--- a/core/modules/file/tests/src/Functional/RemoteFileSaveUploadTest.php
+++ b/core/modules/file/tests/src/Functional/RemoteFileSaveUploadTest.php
@@ -16,6 +16,11 @@ class RemoteFileSaveUploadTest extends SaveUploadTest {
    */
   public static $modules = ['file_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     $this->config('system.file')->set('default_scheme', 'dummy-remote')->save();
diff --git a/core/modules/file/tests/src/Functional/Rest/FileJsonAnonTest.php b/core/modules/file/tests/src/Functional/Rest/FileJsonAnonTest.php
index 5d76ea24735c..9df9bc8489d4 100644
--- a/core/modules/file/tests/src/Functional/Rest/FileJsonAnonTest.php
+++ b/core/modules/file/tests/src/Functional/Rest/FileJsonAnonTest.php
@@ -21,4 +21,9 @@ class FileJsonAnonTest extends FileResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/file/tests/src/Functional/Rest/FileJsonBasicAuthTest.php b/core/modules/file/tests/src/Functional/Rest/FileJsonBasicAuthTest.php
index 87a65ac359d7..a327a0d9d7ad 100644
--- a/core/modules/file/tests/src/Functional/Rest/FileJsonBasicAuthTest.php
+++ b/core/modules/file/tests/src/Functional/Rest/FileJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class FileJsonBasicAuthTest extends FileResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/file/tests/src/Functional/Rest/FileJsonCookieTest.php b/core/modules/file/tests/src/Functional/Rest/FileJsonCookieTest.php
index 9c797207dcd1..8ca3fe1efa7d 100644
--- a/core/modules/file/tests/src/Functional/Rest/FileJsonCookieTest.php
+++ b/core/modules/file/tests/src/Functional/Rest/FileJsonCookieTest.php
@@ -26,4 +26,9 @@ class FileJsonCookieTest extends FileResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/file/tests/src/Functional/Rest/FileXmlAnonTest.php b/core/modules/file/tests/src/Functional/Rest/FileXmlAnonTest.php
index 8360096fb9b5..d14cc48670ac 100644
--- a/core/modules/file/tests/src/Functional/Rest/FileXmlAnonTest.php
+++ b/core/modules/file/tests/src/Functional/Rest/FileXmlAnonTest.php
@@ -23,4 +23,9 @@ class FileXmlAnonTest extends FileResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/file/tests/src/Functional/Rest/FileXmlBasicAuthTest.php b/core/modules/file/tests/src/Functional/Rest/FileXmlBasicAuthTest.php
index 66e9986dbc0f..e0e0030239be 100644
--- a/core/modules/file/tests/src/Functional/Rest/FileXmlBasicAuthTest.php
+++ b/core/modules/file/tests/src/Functional/Rest/FileXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class FileXmlBasicAuthTest extends FileResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/file/tests/src/Functional/Rest/FileXmlCookieTest.php b/core/modules/file/tests/src/Functional/Rest/FileXmlCookieTest.php
index 4b7db031e50b..308f0247f90e 100644
--- a/core/modules/file/tests/src/Functional/Rest/FileXmlCookieTest.php
+++ b/core/modules/file/tests/src/Functional/Rest/FileXmlCookieTest.php
@@ -28,4 +28,9 @@ class FileXmlCookieTest extends FileResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/file/tests/src/Functional/SaveUploadFormTest.php b/core/modules/file/tests/src/Functional/SaveUploadFormTest.php
index de1a4ff0157e..b4d7676d198f 100644
--- a/core/modules/file/tests/src/Functional/SaveUploadFormTest.php
+++ b/core/modules/file/tests/src/Functional/SaveUploadFormTest.php
@@ -26,6 +26,11 @@ class SaveUploadFormTest extends FileManagedTestBase {
    */
   public static $modules = ['dblog'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * An image file path for uploading.
    *
diff --git a/core/modules/file/tests/src/Functional/SaveUploadTest.php b/core/modules/file/tests/src/Functional/SaveUploadTest.php
index 920b4fe139da..8e5c1f1ae636 100644
--- a/core/modules/file/tests/src/Functional/SaveUploadTest.php
+++ b/core/modules/file/tests/src/Functional/SaveUploadTest.php
@@ -26,6 +26,11 @@ class SaveUploadTest extends FileManagedTestBase {
    */
   public static $modules = ['dblog'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * An image file path for uploading.
    *
diff --git a/core/modules/file/tests/src/Functional/Views/RelationshipUserFileDataTest.php b/core/modules/file/tests/src/Functional/Views/RelationshipUserFileDataTest.php
index 887b6384fac4..8f8580d23e7e 100644
--- a/core/modules/file/tests/src/Functional/Views/RelationshipUserFileDataTest.php
+++ b/core/modules/file/tests/src/Functional/Views/RelationshipUserFileDataTest.php
@@ -23,6 +23,11 @@ class RelationshipUserFileDataTest extends ViewTestBase {
    */
   public static $modules = ['file', 'file_test_views', 'user'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/file/tests/src/FunctionalJavascript/AjaxFileManagedMultipleTest.php b/core/modules/file/tests/src/FunctionalJavascript/AjaxFileManagedMultipleTest.php
index c4165a8b3398..9dc76650137c 100644
--- a/core/modules/file/tests/src/FunctionalJavascript/AjaxFileManagedMultipleTest.php
+++ b/core/modules/file/tests/src/FunctionalJavascript/AjaxFileManagedMultipleTest.php
@@ -22,6 +22,11 @@ class AjaxFileManagedMultipleTest extends WebDriverTestBase {
    */
   protected static $modules = ['file_test', 'file', 'file_module_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test if managed file form element works well with multiple files upload.
    */
diff --git a/core/modules/file/tests/src/FunctionalJavascript/FileFieldValidateTest.php b/core/modules/file/tests/src/FunctionalJavascript/FileFieldValidateTest.php
index 99acc3712a01..afbccbbcdde0 100644
--- a/core/modules/file/tests/src/FunctionalJavascript/FileFieldValidateTest.php
+++ b/core/modules/file/tests/src/FunctionalJavascript/FileFieldValidateTest.php
@@ -22,6 +22,11 @@ class FileFieldValidateTest extends WebDriverTestBase {
    */
   public static $modules = ['node', 'file'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test the validation message is displayed only once for ajax uploads.
    */
diff --git a/core/modules/file/tests/src/FunctionalJavascript/FileFieldWidgetTest.php b/core/modules/file/tests/src/FunctionalJavascript/FileFieldWidgetTest.php
index c0d2fc53e04f..b24b381369d2 100644
--- a/core/modules/file/tests/src/FunctionalJavascript/FileFieldWidgetTest.php
+++ b/core/modules/file/tests/src/FunctionalJavascript/FileFieldWidgetTest.php
@@ -32,6 +32,11 @@ class FileFieldWidgetTest extends WebDriverTestBase {
    */
   protected static $modules = ['node', 'file', 'file_module_test', 'field_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/file/tests/src/FunctionalJavascript/FileManagedFileElementTest.php b/core/modules/file/tests/src/FunctionalJavascript/FileManagedFileElementTest.php
index 5ef877b4d048..a4f2c0ca55a4 100644
--- a/core/modules/file/tests/src/FunctionalJavascript/FileManagedFileElementTest.php
+++ b/core/modules/file/tests/src/FunctionalJavascript/FileManagedFileElementTest.php
@@ -16,6 +16,11 @@ class FileManagedFileElementTest extends WebDriverTestBase {
    */
   protected static $modules = ['node', 'file', 'file_module_test', 'field_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with administration permissions.
    *
diff --git a/core/modules/file/tests/src/FunctionalJavascript/MaximumFileSizeExceededUploadTest.php b/core/modules/file/tests/src/FunctionalJavascript/MaximumFileSizeExceededUploadTest.php
index 45c8bf5eec08..69660365a787 100644
--- a/core/modules/file/tests/src/FunctionalJavascript/MaximumFileSizeExceededUploadTest.php
+++ b/core/modules/file/tests/src/FunctionalJavascript/MaximumFileSizeExceededUploadTest.php
@@ -22,6 +22,11 @@ class MaximumFileSizeExceededUploadTest extends WebDriverTestBase {
    */
   public static $modules = ['node', 'file'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The file system service.
    *
diff --git a/core/modules/filter/tests/src/Functional/FilterAdminTest.php b/core/modules/filter/tests/src/Functional/FilterAdminTest.php
index 73289e4cd563..ece059a3e815 100644
--- a/core/modules/filter/tests/src/Functional/FilterAdminTest.php
+++ b/core/modules/filter/tests/src/Functional/FilterAdminTest.php
@@ -22,6 +22,11 @@ class FilterAdminTest extends BrowserTestBase {
    */
   public static $modules = ['block', 'filter', 'node', 'filter_test_plugin', 'dblog'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * An user with administration permissions.
    *
diff --git a/core/modules/filter/tests/src/Functional/FilterDefaultFormatTest.php b/core/modules/filter/tests/src/Functional/FilterDefaultFormatTest.php
index e5a57482a530..d74a14dc6fe8 100644
--- a/core/modules/filter/tests/src/Functional/FilterDefaultFormatTest.php
+++ b/core/modules/filter/tests/src/Functional/FilterDefaultFormatTest.php
@@ -19,6 +19,11 @@ class FilterDefaultFormatTest extends BrowserTestBase {
    */
   public static $modules = ['filter'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests if the default text format is accessible to users.
    */
diff --git a/core/modules/filter/tests/src/Functional/FilterFormTest.php b/core/modules/filter/tests/src/Functional/FilterFormTest.php
index 89b4713ac143..3eb5ae3f8379 100644
--- a/core/modules/filter/tests/src/Functional/FilterFormTest.php
+++ b/core/modules/filter/tests/src/Functional/FilterFormTest.php
@@ -20,6 +20,11 @@ class FilterFormTest extends BrowserTestBase {
    */
   protected static $modules = ['filter', 'filter_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * An administrative user account that can administer text formats.
    *
diff --git a/core/modules/filter/tests/src/Functional/FilterFormatAccessTest.php b/core/modules/filter/tests/src/Functional/FilterFormatAccessTest.php
index f82d258ddfc4..c6ef59b69fbe 100644
--- a/core/modules/filter/tests/src/Functional/FilterFormatAccessTest.php
+++ b/core/modules/filter/tests/src/Functional/FilterFormatAccessTest.php
@@ -21,6 +21,11 @@ class FilterFormatAccessTest extends BrowserTestBase {
    */
   public static $modules = ['block', 'filter', 'node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with administrative permissions.
    *
diff --git a/core/modules/filter/tests/src/Functional/FilterHooksTest.php b/core/modules/filter/tests/src/Functional/FilterHooksTest.php
index 420a7b385560..a70a95f96502 100644
--- a/core/modules/filter/tests/src/Functional/FilterHooksTest.php
+++ b/core/modules/filter/tests/src/Functional/FilterHooksTest.php
@@ -19,6 +19,11 @@ class FilterHooksTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'filter_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests hooks on format management.
    *
diff --git a/core/modules/filter/tests/src/Functional/FilterHtmlImageSecureTest.php b/core/modules/filter/tests/src/Functional/FilterHtmlImageSecureTest.php
index 60ccbc5cc64d..148af99bf9bf 100644
--- a/core/modules/filter/tests/src/Functional/FilterHtmlImageSecureTest.php
+++ b/core/modules/filter/tests/src/Functional/FilterHtmlImageSecureTest.php
@@ -26,6 +26,11 @@ class FilterHtmlImageSecureTest extends BrowserTestBase {
    */
   public static $modules = ['filter', 'node', 'comment'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * An authenticated user.
    *
diff --git a/core/modules/filter/tests/src/Functional/FilterSecurityTest.php b/core/modules/filter/tests/src/Functional/FilterSecurityTest.php
index 4a5b7c49d28e..103c6e3cde85 100644
--- a/core/modules/filter/tests/src/Functional/FilterSecurityTest.php
+++ b/core/modules/filter/tests/src/Functional/FilterSecurityTest.php
@@ -23,6 +23,11 @@ class FilterSecurityTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'filter_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with administrative permissions.
    *
diff --git a/core/modules/filter/tests/src/Functional/Hal/FilterFormatHalJsonAnonTest.php b/core/modules/filter/tests/src/Functional/Hal/FilterFormatHalJsonAnonTest.php
index 3a7c6335f563..8e59a6820d53 100644
--- a/core/modules/filter/tests/src/Functional/Hal/FilterFormatHalJsonAnonTest.php
+++ b/core/modules/filter/tests/src/Functional/Hal/FilterFormatHalJsonAnonTest.php
@@ -17,6 +17,11 @@ class FilterFormatHalJsonAnonTest extends FilterFormatResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/filter/tests/src/Functional/Hal/FilterFormatHalJsonBasicAuthTest.php b/core/modules/filter/tests/src/Functional/Hal/FilterFormatHalJsonBasicAuthTest.php
index c76293d9cc33..00a320cfa54a 100644
--- a/core/modules/filter/tests/src/Functional/Hal/FilterFormatHalJsonBasicAuthTest.php
+++ b/core/modules/filter/tests/src/Functional/Hal/FilterFormatHalJsonBasicAuthTest.php
@@ -17,6 +17,11 @@ class FilterFormatHalJsonBasicAuthTest extends FilterFormatResourceTestBase {
    */
   public static $modules = ['hal', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/filter/tests/src/Functional/Hal/FilterFormatHalJsonCookieTest.php b/core/modules/filter/tests/src/Functional/Hal/FilterFormatHalJsonCookieTest.php
index d2a8654c593d..262d0449aac6 100644
--- a/core/modules/filter/tests/src/Functional/Hal/FilterFormatHalJsonCookieTest.php
+++ b/core/modules/filter/tests/src/Functional/Hal/FilterFormatHalJsonCookieTest.php
@@ -17,6 +17,11 @@ class FilterFormatHalJsonCookieTest extends FilterFormatResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/filter/tests/src/Functional/Rest/FilterFormatJsonAnonTest.php b/core/modules/filter/tests/src/Functional/Rest/FilterFormatJsonAnonTest.php
index 772ccab6ac75..f6aaad0bae13 100644
--- a/core/modules/filter/tests/src/Functional/Rest/FilterFormatJsonAnonTest.php
+++ b/core/modules/filter/tests/src/Functional/Rest/FilterFormatJsonAnonTest.php
@@ -21,4 +21,9 @@ class FilterFormatJsonAnonTest extends FilterFormatResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/filter/tests/src/Functional/Rest/FilterFormatJsonBasicAuthTest.php b/core/modules/filter/tests/src/Functional/Rest/FilterFormatJsonBasicAuthTest.php
index 53ba6ce895a7..10267cf2d2b8 100644
--- a/core/modules/filter/tests/src/Functional/Rest/FilterFormatJsonBasicAuthTest.php
+++ b/core/modules/filter/tests/src/Functional/Rest/FilterFormatJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class FilterFormatJsonBasicAuthTest extends FilterFormatResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/filter/tests/src/Functional/Rest/FilterFormatJsonCookieTest.php b/core/modules/filter/tests/src/Functional/Rest/FilterFormatJsonCookieTest.php
index 432142a7704b..5445fa3e7226 100644
--- a/core/modules/filter/tests/src/Functional/Rest/FilterFormatJsonCookieTest.php
+++ b/core/modules/filter/tests/src/Functional/Rest/FilterFormatJsonCookieTest.php
@@ -26,4 +26,9 @@ class FilterFormatJsonCookieTest extends FilterFormatResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/filter/tests/src/Functional/Rest/FilterFormatXmlAnonTest.php b/core/modules/filter/tests/src/Functional/Rest/FilterFormatXmlAnonTest.php
index 25b84cf621e9..3007fb5f42d5 100644
--- a/core/modules/filter/tests/src/Functional/Rest/FilterFormatXmlAnonTest.php
+++ b/core/modules/filter/tests/src/Functional/Rest/FilterFormatXmlAnonTest.php
@@ -23,4 +23,9 @@ class FilterFormatXmlAnonTest extends FilterFormatResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/filter/tests/src/Functional/Rest/FilterFormatXmlBasicAuthTest.php b/core/modules/filter/tests/src/Functional/Rest/FilterFormatXmlBasicAuthTest.php
index 6c0c62d52b78..8f2c5be0db62 100644
--- a/core/modules/filter/tests/src/Functional/Rest/FilterFormatXmlBasicAuthTest.php
+++ b/core/modules/filter/tests/src/Functional/Rest/FilterFormatXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class FilterFormatXmlBasicAuthTest extends FilterFormatResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/filter/tests/src/Functional/Rest/FilterFormatXmlCookieTest.php b/core/modules/filter/tests/src/Functional/Rest/FilterFormatXmlCookieTest.php
index 1c3be314dd01..e79011a55159 100644
--- a/core/modules/filter/tests/src/Functional/Rest/FilterFormatXmlCookieTest.php
+++ b/core/modules/filter/tests/src/Functional/Rest/FilterFormatXmlCookieTest.php
@@ -28,4 +28,9 @@ class FilterFormatXmlCookieTest extends FilterFormatResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/forum/tests/src/Functional/ForumBlockTest.php b/core/modules/forum/tests/src/Functional/ForumBlockTest.php
index 5bbe1998ee19..a5043fe26586 100644
--- a/core/modules/forum/tests/src/Functional/ForumBlockTest.php
+++ b/core/modules/forum/tests/src/Functional/ForumBlockTest.php
@@ -21,6 +21,11 @@ class ForumBlockTest extends BrowserTestBase {
    */
   public static $modules = ['forum', 'block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with various administrative privileges.
    */
diff --git a/core/modules/forum/tests/src/Functional/ForumIndexTest.php b/core/modules/forum/tests/src/Functional/ForumIndexTest.php
index 5d0ccdff3a70..3bb803a971c8 100644
--- a/core/modules/forum/tests/src/Functional/ForumIndexTest.php
+++ b/core/modules/forum/tests/src/Functional/ForumIndexTest.php
@@ -18,6 +18,11 @@ class ForumIndexTest extends BrowserTestBase {
    */
   public static $modules = ['taxonomy', 'comment', 'forum'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/forum/tests/src/Functional/ForumNodeAccessTest.php b/core/modules/forum/tests/src/Functional/ForumNodeAccessTest.php
index 9849084c6cd6..212bbdd2b5f7 100644
--- a/core/modules/forum/tests/src/Functional/ForumNodeAccessTest.php
+++ b/core/modules/forum/tests/src/Functional/ForumNodeAccessTest.php
@@ -19,6 +19,11 @@ class ForumNodeAccessTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'comment', 'forum', 'taxonomy', 'tracker', 'node_access_test', 'block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     node_access_rebuild();
diff --git a/core/modules/forum/tests/src/Functional/ForumTest.php b/core/modules/forum/tests/src/Functional/ForumTest.php
index d8417ffd042c..d906baf27890 100644
--- a/core/modules/forum/tests/src/Functional/ForumTest.php
+++ b/core/modules/forum/tests/src/Functional/ForumTest.php
@@ -28,6 +28,11 @@ class ForumTest extends BrowserTestBase {
    */
   public static $modules = ['taxonomy', 'comment', 'forum', 'node', 'block', 'menu_ui', 'help'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * A user with various administrative privileges.
    */
diff --git a/core/modules/forum/tests/src/Functional/ForumUninstallTest.php b/core/modules/forum/tests/src/Functional/ForumUninstallTest.php
index 6214bba8f72c..84c81c893377 100644
--- a/core/modules/forum/tests/src/Functional/ForumUninstallTest.php
+++ b/core/modules/forum/tests/src/Functional/ForumUninstallTest.php
@@ -23,6 +23,11 @@ class ForumUninstallTest extends BrowserTestBase {
    */
   public static $modules = ['forum'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests if forum module uninstallation properly deletes the field.
    */
diff --git a/core/modules/forum/tests/src/Functional/Views/ForumIntegrationTest.php b/core/modules/forum/tests/src/Functional/Views/ForumIntegrationTest.php
index 838bee047cab..eda9006f9e1d 100644
--- a/core/modules/forum/tests/src/Functional/Views/ForumIntegrationTest.php
+++ b/core/modules/forum/tests/src/Functional/Views/ForumIntegrationTest.php
@@ -21,6 +21,11 @@ class ForumIntegrationTest extends ViewTestBase {
    */
   public static $modules = ['forum_test_views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/help/tests/src/Functional/ExperimentalHelpTest.php b/core/modules/help/tests/src/Functional/ExperimentalHelpTest.php
index 0eabbda56ba5..ab8d2aca2fb7 100644
--- a/core/modules/help/tests/src/Functional/ExperimentalHelpTest.php
+++ b/core/modules/help/tests/src/Functional/ExperimentalHelpTest.php
@@ -21,6 +21,11 @@ class ExperimentalHelpTest extends BrowserTestBase {
    */
   public static $modules = ['help', 'experimental_module_test', 'help_page_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The admin user.
    *
diff --git a/core/modules/help/tests/src/Functional/HelpBlockTest.php b/core/modules/help/tests/src/Functional/HelpBlockTest.php
index 81c4fc15329a..f4f8db5b1391 100644
--- a/core/modules/help/tests/src/Functional/HelpBlockTest.php
+++ b/core/modules/help/tests/src/Functional/HelpBlockTest.php
@@ -16,6 +16,11 @@ class HelpBlockTest extends BrowserTestBase {
    */
   public static $modules = ['help', 'help_page_test', 'block', 'more_help_page_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The help block instance.
    *
diff --git a/core/modules/help/tests/src/Functional/HelpPageOrderTest.php b/core/modules/help/tests/src/Functional/HelpPageOrderTest.php
index 2981568b6ede..0015ff26fb3c 100644
--- a/core/modules/help/tests/src/Functional/HelpPageOrderTest.php
+++ b/core/modules/help/tests/src/Functional/HelpPageOrderTest.php
@@ -16,6 +16,11 @@ class HelpPageOrderTest extends BrowserTestBase {
    */
   protected static $modules = ['help', 'tour'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Strings to search for on admin/help, in order.
    *
diff --git a/core/modules/help/tests/src/Functional/HelpPageReverseOrderTest.php b/core/modules/help/tests/src/Functional/HelpPageReverseOrderTest.php
index 3920b76fcd37..d31471da9bd6 100644
--- a/core/modules/help/tests/src/Functional/HelpPageReverseOrderTest.php
+++ b/core/modules/help/tests/src/Functional/HelpPageReverseOrderTest.php
@@ -14,6 +14,11 @@ class HelpPageReverseOrderTest extends HelpPageOrderTest {
    */
   protected static $modules = ['more_help_page_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Strings to search for on admin/help, in order.
    *
diff --git a/core/modules/help/tests/src/Functional/HelpTest.php b/core/modules/help/tests/src/Functional/HelpTest.php
index 608263d4c9dc..c78d18cf6f3e 100644
--- a/core/modules/help/tests/src/Functional/HelpTest.php
+++ b/core/modules/help/tests/src/Functional/HelpTest.php
@@ -23,6 +23,11 @@ class HelpTest extends BrowserTestBase {
    */
   public static $modules = ['help_test', 'help_page_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Use the Standard profile to test help implementations of many core modules.
    *
diff --git a/core/modules/help/tests/src/Functional/NoHelpTest.php b/core/modules/help/tests/src/Functional/NoHelpTest.php
index 5df945e35cd0..0b68c0d225eb 100644
--- a/core/modules/help/tests/src/Functional/NoHelpTest.php
+++ b/core/modules/help/tests/src/Functional/NoHelpTest.php
@@ -20,6 +20,11 @@ class NoHelpTest extends BrowserTestBase {
    */
   public static $modules = ['help', 'menu_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The user who will be created.
    */
diff --git a/core/modules/help_topics/tests/src/Functional/HelpTopicSearchTest.php b/core/modules/help_topics/tests/src/Functional/HelpTopicSearchTest.php
index a886167700bc..2f6765c1519a 100644
--- a/core/modules/help_topics/tests/src/Functional/HelpTopicSearchTest.php
+++ b/core/modules/help_topics/tests/src/Functional/HelpTopicSearchTest.php
@@ -23,6 +23,11 @@ class HelpTopicSearchTest extends HelpTopicTranslatedTestBase {
     'language',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/help_topics/tests/src/Functional/HelpTopicTest.php b/core/modules/help_topics/tests/src/Functional/HelpTopicTest.php
index 957021cf6a6c..3dcbbd21c312 100644
--- a/core/modules/help_topics/tests/src/Functional/HelpTopicTest.php
+++ b/core/modules/help_topics/tests/src/Functional/HelpTopicTest.php
@@ -25,6 +25,11 @@ class HelpTopicTest extends BrowserTestBase {
     'block',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The admin user that will be created.
    *
diff --git a/core/modules/help_topics/tests/src/Functional/HelpTopicTranslationTest.php b/core/modules/help_topics/tests/src/Functional/HelpTopicTranslationTest.php
index ead7df35715f..5a45c8c65bf1 100644
--- a/core/modules/help_topics/tests/src/Functional/HelpTopicTranslationTest.php
+++ b/core/modules/help_topics/tests/src/Functional/HelpTopicTranslationTest.php
@@ -9,6 +9,11 @@
  */
 class HelpTopicTranslationTest extends HelpTopicTranslatedTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/help_topics/tests/src/Functional/HelpTopicsSyntaxTest.php b/core/modules/help_topics/tests/src/Functional/HelpTopicsSyntaxTest.php
index b7204cab0a11..6127dd4e8c5e 100644
--- a/core/modules/help_topics/tests/src/Functional/HelpTopicsSyntaxTest.php
+++ b/core/modules/help_topics/tests/src/Functional/HelpTopicsSyntaxTest.php
@@ -30,6 +30,11 @@ class HelpTopicsSyntaxTest extends BrowserTestBase {
     'help_topics',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Tests that all Core help topics can be rendered and have good syntax.
    */
diff --git a/core/modules/history/tests/src/Functional/HistoryTest.php b/core/modules/history/tests/src/Functional/HistoryTest.php
index 415541ed60f7..e6c681620c3b 100644
--- a/core/modules/history/tests/src/Functional/HistoryTest.php
+++ b/core/modules/history/tests/src/Functional/HistoryTest.php
@@ -23,6 +23,11 @@ class HistoryTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'history'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The main user for testing.
    *
diff --git a/core/modules/image/tests/src/Functional/FileMoveTest.php b/core/modules/image/tests/src/Functional/FileMoveTest.php
index fd2536358226..c2a3a1bbe4c9 100644
--- a/core/modules/image/tests/src/Functional/FileMoveTest.php
+++ b/core/modules/image/tests/src/Functional/FileMoveTest.php
@@ -27,6 +27,11 @@ class FileMoveTest extends BrowserTestBase {
    */
   public static $modules = ['image'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests moving a randomly generated image.
    */
diff --git a/core/modules/image/tests/src/Functional/Hal/ImageStyleHalJsonAnonTest.php b/core/modules/image/tests/src/Functional/Hal/ImageStyleHalJsonAnonTest.php
index 61da51f7d0ec..a010f68f0b0c 100644
--- a/core/modules/image/tests/src/Functional/Hal/ImageStyleHalJsonAnonTest.php
+++ b/core/modules/image/tests/src/Functional/Hal/ImageStyleHalJsonAnonTest.php
@@ -17,6 +17,11 @@ class ImageStyleHalJsonAnonTest extends ImageStyleResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/image/tests/src/Functional/Hal/ImageStyleHalJsonBasicAuthTest.php b/core/modules/image/tests/src/Functional/Hal/ImageStyleHalJsonBasicAuthTest.php
index a6ff4941a37a..74a351663f46 100644
--- a/core/modules/image/tests/src/Functional/Hal/ImageStyleHalJsonBasicAuthTest.php
+++ b/core/modules/image/tests/src/Functional/Hal/ImageStyleHalJsonBasicAuthTest.php
@@ -17,6 +17,11 @@ class ImageStyleHalJsonBasicAuthTest extends ImageStyleResourceTestBase {
    */
   public static $modules = ['hal', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/image/tests/src/Functional/Hal/ImageStyleHalJsonCookieTest.php b/core/modules/image/tests/src/Functional/Hal/ImageStyleHalJsonCookieTest.php
index 731e356c9229..e899b6d13efd 100644
--- a/core/modules/image/tests/src/Functional/Hal/ImageStyleHalJsonCookieTest.php
+++ b/core/modules/image/tests/src/Functional/Hal/ImageStyleHalJsonCookieTest.php
@@ -17,6 +17,11 @@ class ImageStyleHalJsonCookieTest extends ImageStyleResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/image/tests/src/Functional/ImageAdminStylesTest.php b/core/modules/image/tests/src/Functional/ImageAdminStylesTest.php
index 30b600bdf149..989a063fb234 100644
--- a/core/modules/image/tests/src/Functional/ImageAdminStylesTest.php
+++ b/core/modules/image/tests/src/Functional/ImageAdminStylesTest.php
@@ -23,6 +23,11 @@ class ImageAdminStylesTest extends ImageFieldTestBase {
     compareFiles as drupalCompareFiles;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Given an image style, generate an image.
    */
diff --git a/core/modules/image/tests/src/Functional/ImageDimensionsTest.php b/core/modules/image/tests/src/Functional/ImageDimensionsTest.php
index 4c80bb1774fc..6a969e5720a7 100644
--- a/core/modules/image/tests/src/Functional/ImageDimensionsTest.php
+++ b/core/modules/image/tests/src/Functional/ImageDimensionsTest.php
@@ -26,6 +26,11 @@ class ImageDimensionsTest extends BrowserTestBase {
    */
   public static $modules = ['image', 'image_module_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   protected $profile = 'testing';
 
   /**
diff --git a/core/modules/image/tests/src/Functional/ImageEffectsTest.php b/core/modules/image/tests/src/Functional/ImageEffectsTest.php
index f6b4ab36e92f..08713f0057a5 100644
--- a/core/modules/image/tests/src/Functional/ImageEffectsTest.php
+++ b/core/modules/image/tests/src/Functional/ImageEffectsTest.php
@@ -19,6 +19,11 @@ class ImageEffectsTest extends ToolkitTestBase {
    */
   public static $modules = ['image', 'image_test', 'image_module_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The image effect manager.
    *
diff --git a/core/modules/image/tests/src/Functional/ImageFieldDefaultImagesTest.php b/core/modules/image/tests/src/Functional/ImageFieldDefaultImagesTest.php
index 34d05c27283f..f081982689c6 100644
--- a/core/modules/image/tests/src/Functional/ImageFieldDefaultImagesTest.php
+++ b/core/modules/image/tests/src/Functional/ImageFieldDefaultImagesTest.php
@@ -33,6 +33,11 @@ class ImageFieldDefaultImagesTest extends ImageFieldTestBase {
    */
   public static $modules = ['field_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests CRUD for fields and field storages with default images.
    */
diff --git a/core/modules/image/tests/src/Functional/ImageFieldDisplayTest.php b/core/modules/image/tests/src/Functional/ImageFieldDisplayTest.php
index c7f5d8c6358b..c99256c9bcd2 100644
--- a/core/modules/image/tests/src/Functional/ImageFieldDisplayTest.php
+++ b/core/modules/image/tests/src/Functional/ImageFieldDisplayTest.php
@@ -34,6 +34,11 @@ class ImageFieldDisplayTest extends ImageFieldTestBase {
    */
   public static $modules = ['field_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Test image formatters on node display for public files.
    */
diff --git a/core/modules/image/tests/src/Functional/ImageFieldValidateTest.php b/core/modules/image/tests/src/Functional/ImageFieldValidateTest.php
index 1e531b23209a..59627521a5a1 100644
--- a/core/modules/image/tests/src/Functional/ImageFieldValidateTest.php
+++ b/core/modules/image/tests/src/Functional/ImageFieldValidateTest.php
@@ -17,6 +17,11 @@ class ImageFieldValidateTest extends ImageFieldTestBase {
     compareFiles as drupalCompareFiles;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test image validity.
    */
diff --git a/core/modules/image/tests/src/Functional/ImageFieldWidgetTest.php b/core/modules/image/tests/src/Functional/ImageFieldWidgetTest.php
index cdec5b905e73..655e7ab8a892 100644
--- a/core/modules/image/tests/src/Functional/ImageFieldWidgetTest.php
+++ b/core/modules/image/tests/src/Functional/ImageFieldWidgetTest.php
@@ -11,6 +11,11 @@
  */
 class ImageFieldWidgetTest extends ImageFieldTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests file widget element.
    */
diff --git a/core/modules/image/tests/src/Functional/ImageOnTranslatedEntityTest.php b/core/modules/image/tests/src/Functional/ImageOnTranslatedEntityTest.php
index e4bde9261c90..c0f01f2719ae 100644
--- a/core/modules/image/tests/src/Functional/ImageOnTranslatedEntityTest.php
+++ b/core/modules/image/tests/src/Functional/ImageOnTranslatedEntityTest.php
@@ -22,6 +22,11 @@ class ImageOnTranslatedEntityTest extends ImageFieldTestBase {
    */
   public static $modules = ['language', 'content_translation', 'field_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The name of the image field used in the test.
    *
diff --git a/core/modules/image/tests/src/Functional/ImageStyleDeleteTest.php b/core/modules/image/tests/src/Functional/ImageStyleDeleteTest.php
index fff27601ce23..71554333b6c8 100644
--- a/core/modules/image/tests/src/Functional/ImageStyleDeleteTest.php
+++ b/core/modules/image/tests/src/Functional/ImageStyleDeleteTest.php
@@ -12,6 +12,11 @@
  */
 class ImageStyleDeleteTest extends ImageFieldTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/image/tests/src/Functional/ImageStyleFlushTest.php b/core/modules/image/tests/src/Functional/ImageStyleFlushTest.php
index 17490119e2ee..a5036eec8f2c 100644
--- a/core/modules/image/tests/src/Functional/ImageStyleFlushTest.php
+++ b/core/modules/image/tests/src/Functional/ImageStyleFlushTest.php
@@ -18,6 +18,11 @@ class ImageStyleFlushTest extends ImageFieldTestBase {
     compareFiles as drupalCompareFiles;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Given an image style and a wrapper, generate an image.
    */
diff --git a/core/modules/image/tests/src/Functional/ImageStylesPathAndUrlTest.php b/core/modules/image/tests/src/Functional/ImageStylesPathAndUrlTest.php
index 381440fe0791..194f6e57a2b9 100644
--- a/core/modules/image/tests/src/Functional/ImageStylesPathAndUrlTest.php
+++ b/core/modules/image/tests/src/Functional/ImageStylesPathAndUrlTest.php
@@ -28,6 +28,11 @@ class ImageStylesPathAndUrlTest extends BrowserTestBase {
    */
   public static $modules = ['image', 'image_module_test', 'language'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The image style.
    *
diff --git a/core/modules/image/tests/src/Functional/QuickEditImageControllerTest.php b/core/modules/image/tests/src/Functional/QuickEditImageControllerTest.php
index a037d4808d66..ab95773a5964 100644
--- a/core/modules/image/tests/src/Functional/QuickEditImageControllerTest.php
+++ b/core/modules/image/tests/src/Functional/QuickEditImageControllerTest.php
@@ -24,6 +24,11 @@ class QuickEditImageControllerTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'image', 'quickedit'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The machine name of our image field.
    *
diff --git a/core/modules/image/tests/src/Functional/Rest/ImageStyleJsonAnonTest.php b/core/modules/image/tests/src/Functional/Rest/ImageStyleJsonAnonTest.php
index e367fb6e6726..a6b62aa34682 100644
--- a/core/modules/image/tests/src/Functional/Rest/ImageStyleJsonAnonTest.php
+++ b/core/modules/image/tests/src/Functional/Rest/ImageStyleJsonAnonTest.php
@@ -21,4 +21,9 @@ class ImageStyleJsonAnonTest extends ImageStyleResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/image/tests/src/Functional/Rest/ImageStyleJsonBasicAuthTest.php b/core/modules/image/tests/src/Functional/Rest/ImageStyleJsonBasicAuthTest.php
index ab6ae57d5323..5d4ba8648e9d 100644
--- a/core/modules/image/tests/src/Functional/Rest/ImageStyleJsonBasicAuthTest.php
+++ b/core/modules/image/tests/src/Functional/Rest/ImageStyleJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class ImageStyleJsonBasicAuthTest extends ImageStyleResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/image/tests/src/Functional/Rest/ImageStyleJsonCookieTest.php b/core/modules/image/tests/src/Functional/Rest/ImageStyleJsonCookieTest.php
index 502123366262..0d0bb88e897b 100644
--- a/core/modules/image/tests/src/Functional/Rest/ImageStyleJsonCookieTest.php
+++ b/core/modules/image/tests/src/Functional/Rest/ImageStyleJsonCookieTest.php
@@ -26,4 +26,9 @@ class ImageStyleJsonCookieTest extends ImageStyleResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/image/tests/src/Functional/Rest/ImageStyleXmlAnonTest.php b/core/modules/image/tests/src/Functional/Rest/ImageStyleXmlAnonTest.php
index 427641aa4b61..8f976f308e8c 100644
--- a/core/modules/image/tests/src/Functional/Rest/ImageStyleXmlAnonTest.php
+++ b/core/modules/image/tests/src/Functional/Rest/ImageStyleXmlAnonTest.php
@@ -23,6 +23,11 @@ class ImageStyleXmlAnonTest extends ImageStyleResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/image/tests/src/Functional/Rest/ImageStyleXmlBasicAuthTest.php b/core/modules/image/tests/src/Functional/Rest/ImageStyleXmlBasicAuthTest.php
index cd376a3140e6..052a50e97a43 100644
--- a/core/modules/image/tests/src/Functional/Rest/ImageStyleXmlBasicAuthTest.php
+++ b/core/modules/image/tests/src/Functional/Rest/ImageStyleXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class ImageStyleXmlBasicAuthTest extends ImageStyleResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/image/tests/src/Functional/Rest/ImageStyleXmlCookieTest.php b/core/modules/image/tests/src/Functional/Rest/ImageStyleXmlCookieTest.php
index 7ca459a0ae08..75554393e31c 100644
--- a/core/modules/image/tests/src/Functional/Rest/ImageStyleXmlCookieTest.php
+++ b/core/modules/image/tests/src/Functional/Rest/ImageStyleXmlCookieTest.php
@@ -28,6 +28,11 @@ class ImageStyleXmlCookieTest extends ImageStyleResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/image/tests/src/FunctionalJavascript/ImageAdminStylesTest.php b/core/modules/image/tests/src/FunctionalJavascript/ImageAdminStylesTest.php
index e573c89a885e..67ad74c25dec 100644
--- a/core/modules/image/tests/src/FunctionalJavascript/ImageAdminStylesTest.php
+++ b/core/modules/image/tests/src/FunctionalJavascript/ImageAdminStylesTest.php
@@ -11,6 +11,11 @@
  */
 class ImageAdminStylesTest extends ImageFieldTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests editing Ajax-enabled image effect forms.
    */
diff --git a/core/modules/image/tests/src/FunctionalJavascript/ImageFieldValidateTest.php b/core/modules/image/tests/src/FunctionalJavascript/ImageFieldValidateTest.php
index 02ca72d19e76..a8907d74c991 100644
--- a/core/modules/image/tests/src/FunctionalJavascript/ImageFieldValidateTest.php
+++ b/core/modules/image/tests/src/FunctionalJavascript/ImageFieldValidateTest.php
@@ -12,6 +12,11 @@
  */
 class ImageFieldValidateTest extends ImageFieldTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test the validation message is displayed only once for ajax uploads.
    */
diff --git a/core/modules/image/tests/src/FunctionalJavascript/QuickEditImageTest.php b/core/modules/image/tests/src/FunctionalJavascript/QuickEditImageTest.php
index b4444eff2b09..2b1dd79dbf66 100644
--- a/core/modules/image/tests/src/FunctionalJavascript/QuickEditImageTest.php
+++ b/core/modules/image/tests/src/FunctionalJavascript/QuickEditImageTest.php
@@ -22,6 +22,11 @@ class QuickEditImageTest extends QuickEditJavascriptTestBase {
    */
   public static $modules = ['node', 'image', 'field_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with permissions to edit Articles and use Quick Edit.
    *
diff --git a/core/modules/inline_form_errors/tests/src/Functional/FormErrorHandlerFileUploadTest.php b/core/modules/inline_form_errors/tests/src/Functional/FormErrorHandlerFileUploadTest.php
index 9535c99fb200..20f4e32132bb 100644
--- a/core/modules/inline_form_errors/tests/src/Functional/FormErrorHandlerFileUploadTest.php
+++ b/core/modules/inline_form_errors/tests/src/Functional/FormErrorHandlerFileUploadTest.php
@@ -21,6 +21,11 @@ class FormErrorHandlerFileUploadTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'file', 'field_ui', 'inline_form_errors'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/inline_form_errors/tests/src/FunctionalJavascript/FormErrorHandlerCKEditorTest.php b/core/modules/inline_form_errors/tests/src/FunctionalJavascript/FormErrorHandlerCKEditorTest.php
index 7c9a74ab5034..a99c1b838792 100644
--- a/core/modules/inline_form_errors/tests/src/FunctionalJavascript/FormErrorHandlerCKEditorTest.php
+++ b/core/modules/inline_form_errors/tests/src/FunctionalJavascript/FormErrorHandlerCKEditorTest.php
@@ -22,6 +22,11 @@ class FormErrorHandlerCKEditorTest extends WebDriverTestBase {
    */
   public static $modules = ['node', 'ckeditor', 'inline_form_errors', 'filter'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/inline_form_errors/tests/src/FunctionalJavascript/FormErrorHandlerQuickEditTest.php b/core/modules/inline_form_errors/tests/src/FunctionalJavascript/FormErrorHandlerQuickEditTest.php
index 00dc3d3f6223..4fcac0f097d3 100644
--- a/core/modules/inline_form_errors/tests/src/FunctionalJavascript/FormErrorHandlerQuickEditTest.php
+++ b/core/modules/inline_form_errors/tests/src/FunctionalJavascript/FormErrorHandlerQuickEditTest.php
@@ -23,6 +23,11 @@ class FormErrorHandlerQuickEditTest extends WebDriverTestBase {
     'inline_form_errors',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * An editor user with permissions to access the in-place editor.
    *
diff --git a/core/modules/jsonapi/tests/src/Functional/ActionTest.php b/core/modules/jsonapi/tests/src/Functional/ActionTest.php
index 796494c21d20..724e08455b58 100644
--- a/core/modules/jsonapi/tests/src/Functional/ActionTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/ActionTest.php
@@ -35,6 +35,11 @@ class ActionTest extends ResourceTestBase {
    */
   protected $entity;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/BaseFieldOverrideTest.php b/core/modules/jsonapi/tests/src/Functional/BaseFieldOverrideTest.php
index 98c56d0502ca..39bdd150cf7b 100644
--- a/core/modules/jsonapi/tests/src/Functional/BaseFieldOverrideTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/BaseFieldOverrideTest.php
@@ -35,6 +35,11 @@ class BaseFieldOverrideTest extends ResourceTestBase {
    */
   protected $entity;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/BlockContentTest.php b/core/modules/jsonapi/tests/src/Functional/BlockContentTest.php
index b06ffdc1be36..d5e51e7a8d92 100644
--- a/core/modules/jsonapi/tests/src/Functional/BlockContentTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/BlockContentTest.php
@@ -39,6 +39,11 @@ class BlockContentTest extends ResourceTestBase {
    */
   protected $entity;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/BlockContentTypeTest.php b/core/modules/jsonapi/tests/src/Functional/BlockContentTypeTest.php
index 0abe7283d053..49268a986b93 100644
--- a/core/modules/jsonapi/tests/src/Functional/BlockContentTypeTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/BlockContentTypeTest.php
@@ -34,6 +34,11 @@ class BlockContentTypeTest extends ResourceTestBase {
    */
   protected $entity;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/BlockTest.php b/core/modules/jsonapi/tests/src/Functional/BlockTest.php
index 3827b0701922..848dfa49f2e9 100644
--- a/core/modules/jsonapi/tests/src/Functional/BlockTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/BlockTest.php
@@ -35,6 +35,11 @@ class BlockTest extends ResourceTestBase {
    */
   protected $entity;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/CommentTest.php b/core/modules/jsonapi/tests/src/Functional/CommentTest.php
index d9fc52ae9f75..4fd1bb786e1e 100644
--- a/core/modules/jsonapi/tests/src/Functional/CommentTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/CommentTest.php
@@ -41,6 +41,11 @@ class CommentTest extends ResourceTestBase {
    */
   protected static $resourceTypeName = 'comment--comment';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/CommentTypeTest.php b/core/modules/jsonapi/tests/src/Functional/CommentTypeTest.php
index 26ce5bac8656..fd8c73a99018 100644
--- a/core/modules/jsonapi/tests/src/Functional/CommentTypeTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/CommentTypeTest.php
@@ -34,6 +34,11 @@ class CommentTypeTest extends ResourceTestBase {
    */
   protected $entity;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/ConfigTestTest.php b/core/modules/jsonapi/tests/src/Functional/ConfigTestTest.php
index e6d873d04fd0..3c6c7bd530d8 100644
--- a/core/modules/jsonapi/tests/src/Functional/ConfigTestTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/ConfigTestTest.php
@@ -34,6 +34,11 @@ class ConfigTestTest extends ResourceTestBase {
    */
   protected $entity;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/ConfigurableLanguageTest.php b/core/modules/jsonapi/tests/src/Functional/ConfigurableLanguageTest.php
index 3aa479745e85..fd03d5334943 100644
--- a/core/modules/jsonapi/tests/src/Functional/ConfigurableLanguageTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/ConfigurableLanguageTest.php
@@ -38,6 +38,11 @@ class ConfigurableLanguageTest extends ResourceTestBase {
    */
   protected $entity;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/ContactFormTest.php b/core/modules/jsonapi/tests/src/Functional/ContactFormTest.php
index 993cff56ef68..3153e1853c1f 100644
--- a/core/modules/jsonapi/tests/src/Functional/ContactFormTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/ContactFormTest.php
@@ -34,6 +34,11 @@ class ContactFormTest extends ResourceTestBase {
    */
   protected $entity;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/ContentLanguageSettingsTest.php b/core/modules/jsonapi/tests/src/Functional/ContentLanguageSettingsTest.php
index 9eb9da53fef2..597bcbc794b4 100644
--- a/core/modules/jsonapi/tests/src/Functional/ContentLanguageSettingsTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/ContentLanguageSettingsTest.php
@@ -37,6 +37,11 @@ class ContentLanguageSettingsTest extends ResourceTestBase {
    */
   protected $entity;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/DateFormatTest.php b/core/modules/jsonapi/tests/src/Functional/DateFormatTest.php
index 5c1dd997c4b8..18b388e9107c 100644
--- a/core/modules/jsonapi/tests/src/Functional/DateFormatTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/DateFormatTest.php
@@ -39,6 +39,11 @@ class DateFormatTest extends ResourceTestBase {
    */
   protected $entity;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/EditorTest.php b/core/modules/jsonapi/tests/src/Functional/EditorTest.php
index d0ec76b84b8c..9b3c38052979 100644
--- a/core/modules/jsonapi/tests/src/Functional/EditorTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/EditorTest.php
@@ -37,6 +37,11 @@ class EditorTest extends ResourceTestBase {
    */
   protected $entity;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/EntityFormDisplayTest.php b/core/modules/jsonapi/tests/src/Functional/EntityFormDisplayTest.php
index 73190d265555..1f914fec0699 100644
--- a/core/modules/jsonapi/tests/src/Functional/EntityFormDisplayTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/EntityFormDisplayTest.php
@@ -35,6 +35,11 @@ class EntityFormDisplayTest extends ResourceTestBase {
    */
   protected $entity;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/EntityFormModeTest.php b/core/modules/jsonapi/tests/src/Functional/EntityFormModeTest.php
index 9a1c36d7532a..637c77ea8f9a 100644
--- a/core/modules/jsonapi/tests/src/Functional/EntityFormModeTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/EntityFormModeTest.php
@@ -36,6 +36,11 @@ class EntityFormModeTest extends ResourceTestBase {
    */
   protected $entity;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/EntityTestMapFieldTest.php b/core/modules/jsonapi/tests/src/Functional/EntityTestMapFieldTest.php
index b78f96cd7846..82cea77007b5 100644
--- a/core/modules/jsonapi/tests/src/Functional/EntityTestMapFieldTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/EntityTestMapFieldTest.php
@@ -56,6 +56,11 @@ class EntityTestMapFieldTest extends ResourceTestBase {
     ],
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/EntityTestTest.php b/core/modules/jsonapi/tests/src/Functional/EntityTestTest.php
index fd3bf6b3a35f..fd6836eab3db 100644
--- a/core/modules/jsonapi/tests/src/Functional/EntityTestTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/EntityTestTest.php
@@ -23,6 +23,11 @@ class EntityTestTest extends ResourceTestBase {
    */
   public static $modules = ['entity_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/EntityViewDisplayTest.php b/core/modules/jsonapi/tests/src/Functional/EntityViewDisplayTest.php
index 1b154cc10ec1..0026706d3f4e 100644
--- a/core/modules/jsonapi/tests/src/Functional/EntityViewDisplayTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/EntityViewDisplayTest.php
@@ -18,6 +18,11 @@ class EntityViewDisplayTest extends ResourceTestBase {
    */
   public static $modules = ['node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/EntityViewModeTest.php b/core/modules/jsonapi/tests/src/Functional/EntityViewModeTest.php
index 991b35fc9339..839b1fae68ac 100644
--- a/core/modules/jsonapi/tests/src/Functional/EntityViewModeTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/EntityViewModeTest.php
@@ -19,6 +19,11 @@ class EntityViewModeTest extends ResourceTestBase {
    */
   public static $modules = ['user', 'field_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/EntryPointTest.php b/core/modules/jsonapi/tests/src/Functional/EntryPointTest.php
index 2934ba066673..2ab8da8c080b 100644
--- a/core/modules/jsonapi/tests/src/Functional/EntryPointTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/EntryPointTest.php
@@ -29,6 +29,11 @@ class EntryPointTest extends BrowserTestBase {
     'basic_auth',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test GETing the entry point.
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/ExternalNormalizersTest.php b/core/modules/jsonapi/tests/src/Functional/ExternalNormalizersTest.php
index 8d7218b988f7..33f6aab0de9d 100644
--- a/core/modules/jsonapi/tests/src/Functional/ExternalNormalizersTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/ExternalNormalizersTest.php
@@ -21,6 +21,11 @@
  */
 class ExternalNormalizersTest extends BrowserTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The original value for the test field.
    *
diff --git a/core/modules/jsonapi/tests/src/Functional/FeedTest.php b/core/modules/jsonapi/tests/src/Functional/FeedTest.php
index 5ca4f906f670..7944a95c604e 100644
--- a/core/modules/jsonapi/tests/src/Functional/FeedTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/FeedTest.php
@@ -20,6 +20,11 @@ class FeedTest extends ResourceTestBase {
    */
   public static $modules = ['aggregator'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/FieldConfigTest.php b/core/modules/jsonapi/tests/src/Functional/FieldConfigTest.php
index 311c098e43ed..25a3889f4573 100644
--- a/core/modules/jsonapi/tests/src/Functional/FieldConfigTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/FieldConfigTest.php
@@ -21,6 +21,11 @@ class FieldConfigTest extends ResourceTestBase {
    */
   public static $modules = ['field', 'node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/FieldStorageConfigTest.php b/core/modules/jsonapi/tests/src/Functional/FieldStorageConfigTest.php
index 0f75906bbb0d..6e03be126154 100644
--- a/core/modules/jsonapi/tests/src/Functional/FieldStorageConfigTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/FieldStorageConfigTest.php
@@ -17,6 +17,11 @@ class FieldStorageConfigTest extends ResourceTestBase {
    */
   public static $modules = ['node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/FileTest.php b/core/modules/jsonapi/tests/src/Functional/FileTest.php
index ff674174ed44..deaa5be82656 100644
--- a/core/modules/jsonapi/tests/src/Functional/FileTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/FileTest.php
@@ -26,6 +26,11 @@ class FileTest extends ResourceTestBase {
    */
   public static $modules = ['file', 'user'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/FileUploadTest.php b/core/modules/jsonapi/tests/src/Functional/FileUploadTest.php
index e57b81469990..3561ebae6559 100644
--- a/core/modules/jsonapi/tests/src/Functional/FileUploadTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/FileUploadTest.php
@@ -27,6 +27,11 @@ class FileUploadTest extends ResourceTestBase {
    */
   public static $modules = ['entity_test', 'file'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    *
diff --git a/core/modules/jsonapi/tests/src/Functional/FilterFormatTest.php b/core/modules/jsonapi/tests/src/Functional/FilterFormatTest.php
index 8af68bb36377..c5b581d9ac71 100644
--- a/core/modules/jsonapi/tests/src/Functional/FilterFormatTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/FilterFormatTest.php
@@ -17,6 +17,11 @@ class FilterFormatTest extends ResourceTestBase {
    */
   public static $modules = ['filter'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/ImageStyleTest.php b/core/modules/jsonapi/tests/src/Functional/ImageStyleTest.php
index 55193d81a5ac..47ec1ace8ccb 100644
--- a/core/modules/jsonapi/tests/src/Functional/ImageStyleTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/ImageStyleTest.php
@@ -17,6 +17,11 @@ class ImageStyleTest extends ResourceTestBase {
    */
   public static $modules = ['image'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/InternalEntitiesTest.php b/core/modules/jsonapi/tests/src/Functional/InternalEntitiesTest.php
index e170222a086e..a0550d15976c 100644
--- a/core/modules/jsonapi/tests/src/Functional/InternalEntitiesTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/InternalEntitiesTest.php
@@ -30,6 +30,11 @@ class InternalEntitiesTest extends BrowserTestBase {
     'serialization',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A test user.
    *
diff --git a/core/modules/jsonapi/tests/src/Functional/ItemTest.php b/core/modules/jsonapi/tests/src/Functional/ItemTest.php
index 6e3a48f027ab..eae850acc2d3 100644
--- a/core/modules/jsonapi/tests/src/Functional/ItemTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/ItemTest.php
@@ -20,6 +20,11 @@ class ItemTest extends ResourceTestBase {
    */
   public static $modules = ['aggregator'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/JsonApiFunctionalMultilingualTest.php b/core/modules/jsonapi/tests/src/Functional/JsonApiFunctionalMultilingualTest.php
index 65cdf3c8baff..4748d68bcc4e 100644
--- a/core/modules/jsonapi/tests/src/Functional/JsonApiFunctionalMultilingualTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/JsonApiFunctionalMultilingualTest.php
@@ -28,6 +28,11 @@ class JsonApiFunctionalMultilingualTest extends JsonApiFunctionalTestBase {
     'content_translation',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/JsonApiFunctionalTest.php b/core/modules/jsonapi/tests/src/Functional/JsonApiFunctionalTest.php
index bae30d70040b..3acde839e798 100644
--- a/core/modules/jsonapi/tests/src/Functional/JsonApiFunctionalTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/JsonApiFunctionalTest.php
@@ -23,6 +23,11 @@ class JsonApiFunctionalTest extends JsonApiFunctionalTestBase {
     'basic_auth',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test the GET method.
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/JsonApiFunctionalTestBase.php b/core/modules/jsonapi/tests/src/Functional/JsonApiFunctionalTestBase.php
index bca821d014f7..f907ccfc4de9 100644
--- a/core/modules/jsonapi/tests/src/Functional/JsonApiFunctionalTestBase.php
+++ b/core/modules/jsonapi/tests/src/Functional/JsonApiFunctionalTestBase.php
@@ -42,6 +42,11 @@ abstract class JsonApiFunctionalTestBase extends BrowserTestBase {
     'link',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test user.
    *
diff --git a/core/modules/jsonapi/tests/src/Functional/JsonApiRegressionTest.php b/core/modules/jsonapi/tests/src/Functional/JsonApiRegressionTest.php
index d8ba8bb94b01..2aec3d96a567 100644
--- a/core/modules/jsonapi/tests/src/Functional/JsonApiRegressionTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/JsonApiRegressionTest.php
@@ -43,6 +43,11 @@ class JsonApiRegressionTest extends JsonApiFunctionalTestBase {
     'basic_auth',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Ensure filtering on relationships works with bundle-specific target types.
    *
diff --git a/core/modules/jsonapi/tests/src/Functional/MediaTest.php b/core/modules/jsonapi/tests/src/Functional/MediaTest.php
index ba7e63e662c6..f604ca60924d 100644
--- a/core/modules/jsonapi/tests/src/Functional/MediaTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/MediaTest.php
@@ -24,6 +24,11 @@ class MediaTest extends ResourceTestBase {
    */
   public static $modules = ['media'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/MediaTypeTest.php b/core/modules/jsonapi/tests/src/Functional/MediaTypeTest.php
index 3e2a0151ec2a..8ae5e1bb78a5 100644
--- a/core/modules/jsonapi/tests/src/Functional/MediaTypeTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/MediaTypeTest.php
@@ -17,6 +17,11 @@ class MediaTypeTest extends ResourceTestBase {
    */
   public static $modules = ['media'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/MenuLinkContentTest.php b/core/modules/jsonapi/tests/src/Functional/MenuLinkContentTest.php
index 41e68aede33cc54e76e5024373c91ba2b893b9db..847c49ff93d579ada017d090f8533f6fb5492dd2 100644
GIT binary patch
delta 40
vcmeBixahFKjA`-%CQfmcl+?7u(wvfzjMUsz1zQF6;*!LoZ1v58OuuCTDmD%!

delta 12
TcmccU(BrVdjA?T<(=}NDB9H{>

diff --git a/core/modules/jsonapi/tests/src/Functional/MenuTest.php b/core/modules/jsonapi/tests/src/Functional/MenuTest.php
index 2acb15f01a26..6a6d9946a347 100644
--- a/core/modules/jsonapi/tests/src/Functional/MenuTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/MenuTest.php
@@ -17,6 +17,11 @@ class MenuTest extends ResourceTestBase {
    */
   public static $modules = [];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/MessageTest.php b/core/modules/jsonapi/tests/src/Functional/MessageTest.php
index 9b9ddf71a9f9..5fcb72512bf9 100644
--- a/core/modules/jsonapi/tests/src/Functional/MessageTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/MessageTest.php
@@ -21,6 +21,11 @@ class MessageTest extends ResourceTestBase {
    */
   public static $modules = ['contact'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/NodeTest.php b/core/modules/jsonapi/tests/src/Functional/NodeTest.php
index 3b3e830d791b..8493da6717af 100644
--- a/core/modules/jsonapi/tests/src/Functional/NodeTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/NodeTest.php
@@ -28,6 +28,11 @@ class NodeTest extends ResourceTestBase {
    */
   public static $modules = ['node', 'path'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/NodeTypeTest.php b/core/modules/jsonapi/tests/src/Functional/NodeTypeTest.php
index eeeb4645ae19..c7bc3e22230e 100644
--- a/core/modules/jsonapi/tests/src/Functional/NodeTypeTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/NodeTypeTest.php
@@ -17,6 +17,11 @@ class NodeTypeTest extends ResourceTestBase {
    */
   public static $modules = ['node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/PathAliasTest.php b/core/modules/jsonapi/tests/src/Functional/PathAliasTest.php
index 3b80c5f06956..ce2e90465e7c 100644
--- a/core/modules/jsonapi/tests/src/Functional/PathAliasTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/PathAliasTest.php
@@ -18,6 +18,11 @@ class PathAliasTest extends ResourceTestBase {
    */
   public static $modules = ['user'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/RdfMappingTest.php b/core/modules/jsonapi/tests/src/Functional/RdfMappingTest.php
index 2570e9756eff..0082d52a3f16 100644
--- a/core/modules/jsonapi/tests/src/Functional/RdfMappingTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/RdfMappingTest.php
@@ -18,6 +18,11 @@ class RdfMappingTest extends ResourceTestBase {
    */
   public static $modules = ['node', 'rdf'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/ResponsiveImageStyleTest.php b/core/modules/jsonapi/tests/src/Functional/ResponsiveImageStyleTest.php
index 298dc48d0099..d70d4b75ec53 100644
--- a/core/modules/jsonapi/tests/src/Functional/ResponsiveImageStyleTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/ResponsiveImageStyleTest.php
@@ -17,6 +17,11 @@ class ResponsiveImageStyleTest extends ResourceTestBase {
    */
   public static $modules = ['responsive_image'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/RestExportJsonApiUnsupported.php b/core/modules/jsonapi/tests/src/Functional/RestExportJsonApiUnsupported.php
index 7efe1aa2e189..eb38ccd01165 100644
--- a/core/modules/jsonapi/tests/src/Functional/RestExportJsonApiUnsupported.php
+++ b/core/modules/jsonapi/tests/src/Functional/RestExportJsonApiUnsupported.php
@@ -24,6 +24,11 @@ class RestExportJsonApiUnsupported extends ViewTestBase {
    */
   public static $modules = ['jsonapi', 'rest_test_views', 'views_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/RestJsonApiUnsupported.php b/core/modules/jsonapi/tests/src/Functional/RestJsonApiUnsupported.php
index 8577caca29f4..27cc2b221929 100644
--- a/core/modules/jsonapi/tests/src/Functional/RestJsonApiUnsupported.php
+++ b/core/modules/jsonapi/tests/src/Functional/RestJsonApiUnsupported.php
@@ -24,6 +24,11 @@ class RestJsonApiUnsupported extends ResourceTestBase {
    */
   public static $modules = ['jsonapi', 'node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/RestResourceConfigTest.php b/core/modules/jsonapi/tests/src/Functional/RestResourceConfigTest.php
index f44ebd0decf4..b1de33b048f7 100644
--- a/core/modules/jsonapi/tests/src/Functional/RestResourceConfigTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/RestResourceConfigTest.php
@@ -17,6 +17,11 @@ class RestResourceConfigTest extends ResourceTestBase {
    */
   public static $modules = ['rest', 'dblog'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/RoleTest.php b/core/modules/jsonapi/tests/src/Functional/RoleTest.php
index 4f8d609a220b..c3ad6e4608de 100644
--- a/core/modules/jsonapi/tests/src/Functional/RoleTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/RoleTest.php
@@ -18,6 +18,11 @@ class RoleTest extends ResourceTestBase {
    */
   public static $modules = ['user'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/SearchPageTest.php b/core/modules/jsonapi/tests/src/Functional/SearchPageTest.php
index 4f741d6335a1..ebf9275f0b7c 100644
--- a/core/modules/jsonapi/tests/src/Functional/SearchPageTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/SearchPageTest.php
@@ -17,6 +17,11 @@ class SearchPageTest extends ResourceTestBase {
    */
   public static $modules = ['node', 'search'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/ShortcutSetTest.php b/core/modules/jsonapi/tests/src/Functional/ShortcutSetTest.php
index 0ab41a38b05f..a6bcce4ece2b 100644
--- a/core/modules/jsonapi/tests/src/Functional/ShortcutSetTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/ShortcutSetTest.php
@@ -17,6 +17,11 @@ class ShortcutSetTest extends ResourceTestBase {
    */
   public static $modules = ['shortcut'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/ShortcutTest.php b/core/modules/jsonapi/tests/src/Functional/ShortcutTest.php
index 1cbb9caeddf8..925bef47382f 100644
--- a/core/modules/jsonapi/tests/src/Functional/ShortcutTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/ShortcutTest.php
@@ -25,6 +25,11 @@ class ShortcutTest extends ResourceTestBase {
    */
   public static $modules = ['comment', 'shortcut'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/TermTest.php b/core/modules/jsonapi/tests/src/Functional/TermTest.php
index 2aecdb5e0c08..f5f20aeec250 100644
--- a/core/modules/jsonapi/tests/src/Functional/TermTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/TermTest.php
@@ -26,6 +26,11 @@ class TermTest extends ResourceTestBase {
    */
   public static $modules = ['taxonomy', 'path'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/TestCoverageTest.php b/core/modules/jsonapi/tests/src/Functional/TestCoverageTest.php
index b3a2c6083b80..92de8b451f70 100644
--- a/core/modules/jsonapi/tests/src/Functional/TestCoverageTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/TestCoverageTest.php
@@ -19,6 +19,11 @@ class TestCoverageTest extends BrowserTestBase {
    */
   protected $definitions;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/TourTest.php b/core/modules/jsonapi/tests/src/Functional/TourTest.php
index e6d3488778e0..80b1ea8c3cdd 100644
--- a/core/modules/jsonapi/tests/src/Functional/TourTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/TourTest.php
@@ -17,6 +17,11 @@ class TourTest extends ResourceTestBase {
    */
   public static $modules = ['tour'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/UserTest.php b/core/modules/jsonapi/tests/src/Functional/UserTest.php
index e9aa7b6bf319..f4ce93f2aa91 100644
--- a/core/modules/jsonapi/tests/src/Functional/UserTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/UserTest.php
@@ -24,6 +24,11 @@ class UserTest extends ResourceTestBase {
    */
   public static $modules = ['user', 'jsonapi_test_user'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/ViewTest.php b/core/modules/jsonapi/tests/src/Functional/ViewTest.php
index 236e8326ee36..3817541f1fc6 100644
--- a/core/modules/jsonapi/tests/src/Functional/ViewTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/ViewTest.php
@@ -17,6 +17,11 @@ class ViewTest extends ResourceTestBase {
    */
   public static $modules = ['views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/VocabularyTest.php b/core/modules/jsonapi/tests/src/Functional/VocabularyTest.php
index 61ecdc811a6d..a3e2a066cf7c 100644
--- a/core/modules/jsonapi/tests/src/Functional/VocabularyTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/VocabularyTest.php
@@ -17,6 +17,11 @@ class VocabularyTest extends ResourceTestBase {
    */
   public static $modules = ['taxonomy'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/jsonapi/tests/src/Functional/WorkflowTest.php b/core/modules/jsonapi/tests/src/Functional/WorkflowTest.php
index 6ad93d50f772..50ffd46fb17a 100644
--- a/core/modules/jsonapi/tests/src/Functional/WorkflowTest.php
+++ b/core/modules/jsonapi/tests/src/Functional/WorkflowTest.php
@@ -17,6 +17,11 @@ class WorkflowTest extends ResourceTestBase {
    */
   public static $modules = ['workflows', 'workflow_type_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/language/tests/src/Functional/AdminPathEntityConverterLanguageTest.php b/core/modules/language/tests/src/Functional/AdminPathEntityConverterLanguageTest.php
index f689a9233fee..a9ea8cc8ce7d 100644
--- a/core/modules/language/tests/src/Functional/AdminPathEntityConverterLanguageTest.php
+++ b/core/modules/language/tests/src/Functional/AdminPathEntityConverterLanguageTest.php
@@ -14,6 +14,11 @@ class AdminPathEntityConverterLanguageTest extends BrowserTestBase {
 
   public static $modules = ['language', 'language_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     $permissions = [
diff --git a/core/modules/language/tests/src/Functional/ConfigurableLanguageManagerTest.php b/core/modules/language/tests/src/Functional/ConfigurableLanguageManagerTest.php
index f1732920c4f8..49d9c0823e10 100644
--- a/core/modules/language/tests/src/Functional/ConfigurableLanguageManagerTest.php
+++ b/core/modules/language/tests/src/Functional/ConfigurableLanguageManagerTest.php
@@ -34,6 +34,11 @@ class ConfigurableLanguageManagerTest extends BrowserTestBase {
     'user',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/language/tests/src/Functional/EntityTypeWithoutLanguageFormTest.php b/core/modules/language/tests/src/Functional/EntityTypeWithoutLanguageFormTest.php
index f7b6191484db..b5d85afd24fc 100644
--- a/core/modules/language/tests/src/Functional/EntityTypeWithoutLanguageFormTest.php
+++ b/core/modules/language/tests/src/Functional/EntityTypeWithoutLanguageFormTest.php
@@ -24,6 +24,11 @@ class EntityTypeWithoutLanguageFormTest extends BrowserTestBase {
     'language_test',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/language/tests/src/Functional/Hal/ConfigurableLanguageHalJsonAnonTest.php b/core/modules/language/tests/src/Functional/Hal/ConfigurableLanguageHalJsonAnonTest.php
index c548c17241d5..f2759d93f8fb 100644
--- a/core/modules/language/tests/src/Functional/Hal/ConfigurableLanguageHalJsonAnonTest.php
+++ b/core/modules/language/tests/src/Functional/Hal/ConfigurableLanguageHalJsonAnonTest.php
@@ -17,6 +17,11 @@ class ConfigurableLanguageHalJsonAnonTest extends ConfigurableLanguageResourceTe
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/language/tests/src/Functional/Hal/ConfigurableLanguageHalJsonBasicAuthTest.php b/core/modules/language/tests/src/Functional/Hal/ConfigurableLanguageHalJsonBasicAuthTest.php
index 4647acb82a08..f0803aa55390 100644
--- a/core/modules/language/tests/src/Functional/Hal/ConfigurableLanguageHalJsonBasicAuthTest.php
+++ b/core/modules/language/tests/src/Functional/Hal/ConfigurableLanguageHalJsonBasicAuthTest.php
@@ -17,6 +17,11 @@ class ConfigurableLanguageHalJsonBasicAuthTest extends ConfigurableLanguageResou
    */
   public static $modules = ['hal', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/language/tests/src/Functional/Hal/ConfigurableLanguageHalJsonCookieTest.php b/core/modules/language/tests/src/Functional/Hal/ConfigurableLanguageHalJsonCookieTest.php
index 9ad756106743..68fe2bf4524d 100644
--- a/core/modules/language/tests/src/Functional/Hal/ConfigurableLanguageHalJsonCookieTest.php
+++ b/core/modules/language/tests/src/Functional/Hal/ConfigurableLanguageHalJsonCookieTest.php
@@ -17,6 +17,11 @@ class ConfigurableLanguageHalJsonCookieTest extends ConfigurableLanguageResource
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/language/tests/src/Functional/Hal/ContentLanguageSettingsHalJsonAnonTest.php b/core/modules/language/tests/src/Functional/Hal/ContentLanguageSettingsHalJsonAnonTest.php
index d5b7947ed47e..88bf96eb1d20 100644
--- a/core/modules/language/tests/src/Functional/Hal/ContentLanguageSettingsHalJsonAnonTest.php
+++ b/core/modules/language/tests/src/Functional/Hal/ContentLanguageSettingsHalJsonAnonTest.php
@@ -17,6 +17,11 @@ class ContentLanguageSettingsHalJsonAnonTest extends ContentLanguageSettingsReso
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/language/tests/src/Functional/Hal/ContentLanguageSettingsHalJsonBasicAuthTest.php b/core/modules/language/tests/src/Functional/Hal/ContentLanguageSettingsHalJsonBasicAuthTest.php
index fefd0db73a7a..ec6f172a597f 100644
--- a/core/modules/language/tests/src/Functional/Hal/ContentLanguageSettingsHalJsonBasicAuthTest.php
+++ b/core/modules/language/tests/src/Functional/Hal/ContentLanguageSettingsHalJsonBasicAuthTest.php
@@ -17,6 +17,11 @@ class ContentLanguageSettingsHalJsonBasicAuthTest extends ContentLanguageSetting
    */
   public static $modules = ['hal', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/language/tests/src/Functional/Hal/ContentLanguageSettingsHalJsonCookieTest.php b/core/modules/language/tests/src/Functional/Hal/ContentLanguageSettingsHalJsonCookieTest.php
index 63584f648977..e9ed29cf3549 100644
--- a/core/modules/language/tests/src/Functional/Hal/ContentLanguageSettingsHalJsonCookieTest.php
+++ b/core/modules/language/tests/src/Functional/Hal/ContentLanguageSettingsHalJsonCookieTest.php
@@ -17,6 +17,11 @@ class ContentLanguageSettingsHalJsonCookieTest extends ContentLanguageSettingsRe
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/language/tests/src/Functional/LanguageBlockSettingsVisibilityTest.php b/core/modules/language/tests/src/Functional/LanguageBlockSettingsVisibilityTest.php
index 003c5a63fa60..1511bf1f1491 100644
--- a/core/modules/language/tests/src/Functional/LanguageBlockSettingsVisibilityTest.php
+++ b/core/modules/language/tests/src/Functional/LanguageBlockSettingsVisibilityTest.php
@@ -13,6 +13,11 @@ class LanguageBlockSettingsVisibilityTest extends BrowserTestBase {
 
   public static $modules = ['block', 'language'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   public function testUnnecessaryLanguageSettingsVisibility() {
     $admin_user = $this->drupalCreateUser(['administer languages', 'access administration pages', 'administer blocks']);
     $this->drupalLogin($admin_user);
diff --git a/core/modules/language/tests/src/Functional/LanguageBreadcrumbTest.php b/core/modules/language/tests/src/Functional/LanguageBreadcrumbTest.php
index e15fcf7a6d67..964da0d04b41 100644
--- a/core/modules/language/tests/src/Functional/LanguageBreadcrumbTest.php
+++ b/core/modules/language/tests/src/Functional/LanguageBreadcrumbTest.php
@@ -19,6 +19,11 @@ class LanguageBreadcrumbTest extends BrowserTestBase {
    */
   public static $modules = ['language', 'block', 'filter'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/language/tests/src/Functional/LanguageBrowserDetectionAcceptLanguageTest.php b/core/modules/language/tests/src/Functional/LanguageBrowserDetectionAcceptLanguageTest.php
index 1d1ea9c59956..849d59f97435 100644
--- a/core/modules/language/tests/src/Functional/LanguageBrowserDetectionAcceptLanguageTest.php
+++ b/core/modules/language/tests/src/Functional/LanguageBrowserDetectionAcceptLanguageTest.php
@@ -19,6 +19,11 @@ class LanguageBrowserDetectionAcceptLanguageTest extends BrowserTestBase {
    */
   public static $modules = ['language', 'locale', 'content_translation', 'system_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/language/tests/src/Functional/LanguageBrowserDetectionTest.php b/core/modules/language/tests/src/Functional/LanguageBrowserDetectionTest.php
index b0b383bdf8cf..6c76a021112e 100644
--- a/core/modules/language/tests/src/Functional/LanguageBrowserDetectionTest.php
+++ b/core/modules/language/tests/src/Functional/LanguageBrowserDetectionTest.php
@@ -14,6 +14,11 @@ class LanguageBrowserDetectionTest extends BrowserTestBase {
 
   public static $modules = ['language'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests for adding, editing and deleting mappings between browser language
    * codes and Drupal language codes.
diff --git a/core/modules/language/tests/src/Functional/LanguageConfigOverrideImportTest.php b/core/modules/language/tests/src/Functional/LanguageConfigOverrideImportTest.php
index 2ddd4963ed3e..03f3df28b518 100644
--- a/core/modules/language/tests/src/Functional/LanguageConfigOverrideImportTest.php
+++ b/core/modules/language/tests/src/Functional/LanguageConfigOverrideImportTest.php
@@ -19,6 +19,11 @@ class LanguageConfigOverrideImportTest extends BrowserTestBase {
    */
   public static $modules = ['language', 'config', 'locale', 'config_translation'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that language can be enabled and overrides are created during a sync.
    */
diff --git a/core/modules/language/tests/src/Functional/LanguageConfigSchemaTest.php b/core/modules/language/tests/src/Functional/LanguageConfigSchemaTest.php
index e19fe53da32e..b2e384161b62 100644
--- a/core/modules/language/tests/src/Functional/LanguageConfigSchemaTest.php
+++ b/core/modules/language/tests/src/Functional/LanguageConfigSchemaTest.php
@@ -21,6 +21,11 @@ class LanguageConfigSchemaTest extends BrowserTestBase {
    */
   public static $modules = ['language', 'menu_link_content'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with administrative permissions.
    *
diff --git a/core/modules/language/tests/src/Functional/LanguageConfigurationElementTest.php b/core/modules/language/tests/src/Functional/LanguageConfigurationElementTest.php
index 7d400cab4cba..5c5640abb489 100644
--- a/core/modules/language/tests/src/Functional/LanguageConfigurationElementTest.php
+++ b/core/modules/language/tests/src/Functional/LanguageConfigurationElementTest.php
@@ -22,6 +22,11 @@ class LanguageConfigurationElementTest extends BrowserTestBase {
    */
   public static $modules = ['taxonomy', 'node', 'language', 'language_elements_test', 'field_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     $user = $this->drupalCreateUser(['access administration pages', 'administer languages', 'administer content types']);
diff --git a/core/modules/language/tests/src/Functional/LanguageConfigurationTest.php b/core/modules/language/tests/src/Functional/LanguageConfigurationTest.php
index 777ff110e824..06f4cee3ba71 100644
--- a/core/modules/language/tests/src/Functional/LanguageConfigurationTest.php
+++ b/core/modules/language/tests/src/Functional/LanguageConfigurationTest.php
@@ -22,6 +22,11 @@ class LanguageConfigurationTest extends BrowserTestBase {
    */
   public static $modules = ['language'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Functional tests for adding, editing and deleting languages.
    */
diff --git a/core/modules/language/tests/src/Functional/LanguageCustomLanguageConfigurationTest.php b/core/modules/language/tests/src/Functional/LanguageCustomLanguageConfigurationTest.php
index ab3148dac362..52bbde11725c 100644
--- a/core/modules/language/tests/src/Functional/LanguageCustomLanguageConfigurationTest.php
+++ b/core/modules/language/tests/src/Functional/LanguageCustomLanguageConfigurationTest.php
@@ -21,6 +21,11 @@ class LanguageCustomLanguageConfigurationTest extends BrowserTestBase {
    */
   public static $modules = ['language'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Functional tests for adding, editing and deleting languages.
    */
diff --git a/core/modules/language/tests/src/Functional/LanguageEntityFieldAccessHookTest.php b/core/modules/language/tests/src/Functional/LanguageEntityFieldAccessHookTest.php
index 19b3217759bb..fac20719d118 100644
--- a/core/modules/language/tests/src/Functional/LanguageEntityFieldAccessHookTest.php
+++ b/core/modules/language/tests/src/Functional/LanguageEntityFieldAccessHookTest.php
@@ -25,6 +25,11 @@ class LanguageEntityFieldAccessHookTest extends BrowserTestBase {
     'language_entity_field_access_test',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests compatibility with hook_entity_field_access().
    */
diff --git a/core/modules/language/tests/src/Functional/LanguageListModuleInstallTest.php b/core/modules/language/tests/src/Functional/LanguageListModuleInstallTest.php
index 013d00d8dbe5..e63c31726c39 100644
--- a/core/modules/language/tests/src/Functional/LanguageListModuleInstallTest.php
+++ b/core/modules/language/tests/src/Functional/LanguageListModuleInstallTest.php
@@ -19,6 +19,11 @@ class LanguageListModuleInstallTest extends BrowserTestBase {
    */
   public static $modules = ['language_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests enabling Language.
    */
diff --git a/core/modules/language/tests/src/Functional/LanguageListTest.php b/core/modules/language/tests/src/Functional/LanguageListTest.php
index 565ae586b343..45ec251ba246 100644
--- a/core/modules/language/tests/src/Functional/LanguageListTest.php
+++ b/core/modules/language/tests/src/Functional/LanguageListTest.php
@@ -22,6 +22,11 @@ class LanguageListTest extends BrowserTestBase {
    */
   public static $modules = ['language'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Functional tests for adding, editing and deleting languages.
    */
diff --git a/core/modules/language/tests/src/Functional/LanguageLocaleListTest.php b/core/modules/language/tests/src/Functional/LanguageLocaleListTest.php
index 844a8af13b5a..2809d329862e 100644
--- a/core/modules/language/tests/src/Functional/LanguageLocaleListTest.php
+++ b/core/modules/language/tests/src/Functional/LanguageLocaleListTest.php
@@ -19,6 +19,11 @@ class LanguageLocaleListTest extends BrowserTestBase {
    */
   public static $modules = ['language', 'locale'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/language/tests/src/Functional/LanguageNegotiationContentEntityTest.php b/core/modules/language/tests/src/Functional/LanguageNegotiationContentEntityTest.php
index b158078e7a02..66ea59ac1eee 100644
--- a/core/modules/language/tests/src/Functional/LanguageNegotiationContentEntityTest.php
+++ b/core/modules/language/tests/src/Functional/LanguageNegotiationContentEntityTest.php
@@ -27,6 +27,11 @@ class LanguageNegotiationContentEntityTest extends BrowserTestBase {
    */
   public static $modules = ['language', 'language_test', 'entity_test', 'system'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The entity being used for testing.
    *
diff --git a/core/modules/language/tests/src/Functional/LanguageNegotiationInfoTest.php b/core/modules/language/tests/src/Functional/LanguageNegotiationInfoTest.php
index 374f748e1e3e..bab82fd8fd6b 100644
--- a/core/modules/language/tests/src/Functional/LanguageNegotiationInfoTest.php
+++ b/core/modules/language/tests/src/Functional/LanguageNegotiationInfoTest.php
@@ -21,6 +21,11 @@ class LanguageNegotiationInfoTest extends BrowserTestBase {
    */
   public static $modules = ['language', 'content_translation'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/language/tests/src/Functional/LanguageNegotiationUrlTest.php b/core/modules/language/tests/src/Functional/LanguageNegotiationUrlTest.php
index 07ae85d4338f..673d08aeb4e5 100644
--- a/core/modules/language/tests/src/Functional/LanguageNegotiationUrlTest.php
+++ b/core/modules/language/tests/src/Functional/LanguageNegotiationUrlTest.php
@@ -22,6 +22,11 @@ class LanguageNegotiationUrlTest extends BrowserTestBase {
     'path',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * @var \Drupal\user\Entity\User
    */
diff --git a/core/modules/language/tests/src/Functional/LanguagePathMonolingualTest.php b/core/modules/language/tests/src/Functional/LanguagePathMonolingualTest.php
index 17ff3f936df7..5c4bcfa01607 100644
--- a/core/modules/language/tests/src/Functional/LanguagePathMonolingualTest.php
+++ b/core/modules/language/tests/src/Functional/LanguagePathMonolingualTest.php
@@ -18,6 +18,11 @@ class LanguagePathMonolingualTest extends BrowserTestBase {
    */
   public static $modules = ['block', 'language', 'path'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/language/tests/src/Functional/LanguageSelectorTranslatableTest.php b/core/modules/language/tests/src/Functional/LanguageSelectorTranslatableTest.php
index 9526d226fdd7..67695108517d 100644
--- a/core/modules/language/tests/src/Functional/LanguageSelectorTranslatableTest.php
+++ b/core/modules/language/tests/src/Functional/LanguageSelectorTranslatableTest.php
@@ -26,6 +26,11 @@ class LanguageSelectorTranslatableTest extends BrowserTestBase {
     'locale',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The user with administrator privileges.
    *
diff --git a/core/modules/language/tests/src/Functional/LanguageSwitchingTest.php b/core/modules/language/tests/src/Functional/LanguageSwitchingTest.php
index 1303082c154d..6605a0c7de43 100644
--- a/core/modules/language/tests/src/Functional/LanguageSwitchingTest.php
+++ b/core/modules/language/tests/src/Functional/LanguageSwitchingTest.php
@@ -22,6 +22,11 @@ class LanguageSwitchingTest extends BrowserTestBase {
    */
   public static $modules = ['locale', 'locale_test', 'language', 'block', 'language_test', 'menu_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/language/tests/src/Functional/LanguageTourTest.php b/core/modules/language/tests/src/Functional/LanguageTourTest.php
index 13b29f2ef56f..9bae57720a6c 100644
--- a/core/modules/language/tests/src/Functional/LanguageTourTest.php
+++ b/core/modules/language/tests/src/Functional/LanguageTourTest.php
@@ -25,6 +25,11 @@ class LanguageTourTest extends TourTestBase {
    */
   public static $modules = ['block', 'language', 'tour'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/language/tests/src/Functional/LanguageUILanguageNegotiationTest.php b/core/modules/language/tests/src/Functional/LanguageUILanguageNegotiationTest.php
index 57a6ab66ba26..ebf6366a577a 100644
--- a/core/modules/language/tests/src/Functional/LanguageUILanguageNegotiationTest.php
+++ b/core/modules/language/tests/src/Functional/LanguageUILanguageNegotiationTest.php
@@ -60,6 +60,11 @@ class LanguageUILanguageNegotiationTest extends BrowserTestBase {
    */
   public static $modules = ['locale', 'language_test', 'block', 'user', 'content_translation'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/language/tests/src/Functional/LanguageUrlRewritingTest.php b/core/modules/language/tests/src/Functional/LanguageUrlRewritingTest.php
index 94f6fc6b90e3..49007619dfc1 100644
--- a/core/modules/language/tests/src/Functional/LanguageUrlRewritingTest.php
+++ b/core/modules/language/tests/src/Functional/LanguageUrlRewritingTest.php
@@ -23,6 +23,11 @@ class LanguageUrlRewritingTest extends BrowserTestBase {
    */
   public static $modules = ['language', 'language_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * An user with permissions to administer languages.
    *
diff --git a/core/modules/language/tests/src/Functional/Rest/ConfigurableLanguageJsonAnonTest.php b/core/modules/language/tests/src/Functional/Rest/ConfigurableLanguageJsonAnonTest.php
index 7533e31c0e84..572f2a9512cf 100644
--- a/core/modules/language/tests/src/Functional/Rest/ConfigurableLanguageJsonAnonTest.php
+++ b/core/modules/language/tests/src/Functional/Rest/ConfigurableLanguageJsonAnonTest.php
@@ -21,4 +21,9 @@ class ConfigurableLanguageJsonAnonTest extends ConfigurableLanguageResourceTestB
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/language/tests/src/Functional/Rest/ConfigurableLanguageJsonBasicAuthTest.php b/core/modules/language/tests/src/Functional/Rest/ConfigurableLanguageJsonBasicAuthTest.php
index 5352c9a95119..e61892a299bf 100644
--- a/core/modules/language/tests/src/Functional/Rest/ConfigurableLanguageJsonBasicAuthTest.php
+++ b/core/modules/language/tests/src/Functional/Rest/ConfigurableLanguageJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class ConfigurableLanguageJsonBasicAuthTest extends ConfigurableLanguageResource
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/language/tests/src/Functional/Rest/ConfigurableLanguageJsonCookieTest.php b/core/modules/language/tests/src/Functional/Rest/ConfigurableLanguageJsonCookieTest.php
index cd3d9ce73c34..a1b348b4413a 100644
--- a/core/modules/language/tests/src/Functional/Rest/ConfigurableLanguageJsonCookieTest.php
+++ b/core/modules/language/tests/src/Functional/Rest/ConfigurableLanguageJsonCookieTest.php
@@ -26,4 +26,9 @@ class ConfigurableLanguageJsonCookieTest extends ConfigurableLanguageResourceTes
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/language/tests/src/Functional/Rest/ConfigurableLanguageXmlAnonTest.php b/core/modules/language/tests/src/Functional/Rest/ConfigurableLanguageXmlAnonTest.php
index 882b7bf458f5..c787cd343c7b 100644
--- a/core/modules/language/tests/src/Functional/Rest/ConfigurableLanguageXmlAnonTest.php
+++ b/core/modules/language/tests/src/Functional/Rest/ConfigurableLanguageXmlAnonTest.php
@@ -23,4 +23,9 @@ class ConfigurableLanguageXmlAnonTest extends ConfigurableLanguageResourceTestBa
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/language/tests/src/Functional/Rest/ConfigurableLanguageXmlBasicAuthTest.php b/core/modules/language/tests/src/Functional/Rest/ConfigurableLanguageXmlBasicAuthTest.php
index afc017f7a019..7aff2d00fbb3 100644
--- a/core/modules/language/tests/src/Functional/Rest/ConfigurableLanguageXmlBasicAuthTest.php
+++ b/core/modules/language/tests/src/Functional/Rest/ConfigurableLanguageXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class ConfigurableLanguageXmlBasicAuthTest extends ConfigurableLanguageResourceT
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/language/tests/src/Functional/Rest/ConfigurableLanguageXmlCookieTest.php b/core/modules/language/tests/src/Functional/Rest/ConfigurableLanguageXmlCookieTest.php
index 7755d76e919b..0d874619359f 100644
--- a/core/modules/language/tests/src/Functional/Rest/ConfigurableLanguageXmlCookieTest.php
+++ b/core/modules/language/tests/src/Functional/Rest/ConfigurableLanguageXmlCookieTest.php
@@ -28,4 +28,9 @@ class ConfigurableLanguageXmlCookieTest extends ConfigurableLanguageResourceTest
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/language/tests/src/Functional/Rest/ContentLanguageSettingsJsonAnonTest.php b/core/modules/language/tests/src/Functional/Rest/ContentLanguageSettingsJsonAnonTest.php
index 1bece31007cd..74de3ea30d11 100644
--- a/core/modules/language/tests/src/Functional/Rest/ContentLanguageSettingsJsonAnonTest.php
+++ b/core/modules/language/tests/src/Functional/Rest/ContentLanguageSettingsJsonAnonTest.php
@@ -21,4 +21,9 @@ class ContentLanguageSettingsJsonAnonTest extends ContentLanguageSettingsResourc
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/language/tests/src/Functional/Rest/ContentLanguageSettingsJsonBasicAuthTest.php b/core/modules/language/tests/src/Functional/Rest/ContentLanguageSettingsJsonBasicAuthTest.php
index f1063a3dc11f..d68559fcd009 100644
--- a/core/modules/language/tests/src/Functional/Rest/ContentLanguageSettingsJsonBasicAuthTest.php
+++ b/core/modules/language/tests/src/Functional/Rest/ContentLanguageSettingsJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class ContentLanguageSettingsJsonBasicAuthTest extends ContentLanguageSettingsRe
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/language/tests/src/Functional/Rest/ContentLanguageSettingsJsonCookieTest.php b/core/modules/language/tests/src/Functional/Rest/ContentLanguageSettingsJsonCookieTest.php
index 84da80849c4a..9d38614cacf8 100644
--- a/core/modules/language/tests/src/Functional/Rest/ContentLanguageSettingsJsonCookieTest.php
+++ b/core/modules/language/tests/src/Functional/Rest/ContentLanguageSettingsJsonCookieTest.php
@@ -26,4 +26,9 @@ class ContentLanguageSettingsJsonCookieTest extends ContentLanguageSettingsResou
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/language/tests/src/Functional/Rest/ContentLanguageSettingsXmlAnonTest.php b/core/modules/language/tests/src/Functional/Rest/ContentLanguageSettingsXmlAnonTest.php
index fd6519387e8b..102e85df52c3 100644
--- a/core/modules/language/tests/src/Functional/Rest/ContentLanguageSettingsXmlAnonTest.php
+++ b/core/modules/language/tests/src/Functional/Rest/ContentLanguageSettingsXmlAnonTest.php
@@ -23,4 +23,9 @@ class ContentLanguageSettingsXmlAnonTest extends ContentLanguageSettingsResource
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/language/tests/src/Functional/Rest/ContentLanguageSettingsXmlBasicAuthTest.php b/core/modules/language/tests/src/Functional/Rest/ContentLanguageSettingsXmlBasicAuthTest.php
index dee7ad27d4c9..1d1fad462c91 100644
--- a/core/modules/language/tests/src/Functional/Rest/ContentLanguageSettingsXmlBasicAuthTest.php
+++ b/core/modules/language/tests/src/Functional/Rest/ContentLanguageSettingsXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class ContentLanguageSettingsXmlBasicAuthTest extends ContentLanguageSettingsRes
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/language/tests/src/Functional/Rest/ContentLanguageSettingsXmlCookieTest.php b/core/modules/language/tests/src/Functional/Rest/ContentLanguageSettingsXmlCookieTest.php
index a5b49684f7d6..1c7ede1bf9f5 100644
--- a/core/modules/language/tests/src/Functional/Rest/ContentLanguageSettingsXmlCookieTest.php
+++ b/core/modules/language/tests/src/Functional/Rest/ContentLanguageSettingsXmlCookieTest.php
@@ -28,4 +28,9 @@ class ContentLanguageSettingsXmlCookieTest extends ContentLanguageSettingsResour
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/layout_builder/tests/src/Functional/Hal/LayoutBuilderEntityViewDisplayHalJsonAnonTest.php b/core/modules/layout_builder/tests/src/Functional/Hal/LayoutBuilderEntityViewDisplayHalJsonAnonTest.php
index 1740380108da..73da4c9b11f0 100644
--- a/core/modules/layout_builder/tests/src/Functional/Hal/LayoutBuilderEntityViewDisplayHalJsonAnonTest.php
+++ b/core/modules/layout_builder/tests/src/Functional/Hal/LayoutBuilderEntityViewDisplayHalJsonAnonTest.php
@@ -28,4 +28,9 @@ class LayoutBuilderEntityViewDisplayHalJsonAnonTest extends LayoutBuilderEntityV
    */
   protected static $mimeType = 'application/hal+json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/layout_builder/tests/src/Functional/Hal/LayoutBuilderEntityViewDisplayHalJsonCookieTest.php b/core/modules/layout_builder/tests/src/Functional/Hal/LayoutBuilderEntityViewDisplayHalJsonCookieTest.php
index bbc17736b7e7..ad272d297e6a 100644
--- a/core/modules/layout_builder/tests/src/Functional/Hal/LayoutBuilderEntityViewDisplayHalJsonCookieTest.php
+++ b/core/modules/layout_builder/tests/src/Functional/Hal/LayoutBuilderEntityViewDisplayHalJsonCookieTest.php
@@ -17,4 +17,9 @@ class LayoutBuilderEntityViewDisplayHalJsonCookieTest extends LayoutBuilderEntit
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/layout_builder/tests/src/Functional/Jsonapi/LayoutBuilderEntityViewDisplayTest.php b/core/modules/layout_builder/tests/src/Functional/Jsonapi/LayoutBuilderEntityViewDisplayTest.php
index f6b76376eb18..628a014483fb 100644
--- a/core/modules/layout_builder/tests/src/Functional/Jsonapi/LayoutBuilderEntityViewDisplayTest.php
+++ b/core/modules/layout_builder/tests/src/Functional/Jsonapi/LayoutBuilderEntityViewDisplayTest.php
@@ -18,6 +18,11 @@ class LayoutBuilderEntityViewDisplayTest extends EntityViewDisplayTest {
    */
   public static $modules = ['layout_builder'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/layout_builder/tests/src/Functional/LayoutBuilderAccessTest.php b/core/modules/layout_builder/tests/src/Functional/LayoutBuilderAccessTest.php
index af503f4ca155..55c69ac176eb 100644
--- a/core/modules/layout_builder/tests/src/Functional/LayoutBuilderAccessTest.php
+++ b/core/modules/layout_builder/tests/src/Functional/LayoutBuilderAccessTest.php
@@ -22,6 +22,11 @@ class LayoutBuilderAccessTest extends BrowserTestBase {
     'user',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/layout_builder/tests/src/Functional/LayoutBuilderFieldBlockThemeSuggestionsTest.php b/core/modules/layout_builder/tests/src/Functional/LayoutBuilderFieldBlockThemeSuggestionsTest.php
index 4d47586dff63..9e465fc0c4c4 100644
--- a/core/modules/layout_builder/tests/src/Functional/LayoutBuilderFieldBlockThemeSuggestionsTest.php
+++ b/core/modules/layout_builder/tests/src/Functional/LayoutBuilderFieldBlockThemeSuggestionsTest.php
@@ -20,6 +20,11 @@ class LayoutBuilderFieldBlockThemeSuggestionsTest extends BrowserTestBase {
     'layout_builder_field_block_theme_suggestions_test',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/layout_builder/tests/src/Functional/LayoutBuilderQuickEditTest.php b/core/modules/layout_builder/tests/src/Functional/LayoutBuilderQuickEditTest.php
index e58f2c613fc6..6d786d2b14e3 100644
--- a/core/modules/layout_builder/tests/src/Functional/LayoutBuilderQuickEditTest.php
+++ b/core/modules/layout_builder/tests/src/Functional/LayoutBuilderQuickEditTest.php
@@ -20,6 +20,11 @@ class LayoutBuilderQuickEditTest extends BrowserTestBase {
     'quickedit',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/layout_builder/tests/src/Functional/LayoutBuilderSectionStorageTest.php b/core/modules/layout_builder/tests/src/Functional/LayoutBuilderSectionStorageTest.php
index 917322893918..828bde2c1e33 100644
--- a/core/modules/layout_builder/tests/src/Functional/LayoutBuilderSectionStorageTest.php
+++ b/core/modules/layout_builder/tests/src/Functional/LayoutBuilderSectionStorageTest.php
@@ -20,6 +20,11 @@ class LayoutBuilderSectionStorageTest extends BrowserTestBase {
     'layout_builder_test',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/layout_builder/tests/src/Functional/LayoutBuilderTest.php b/core/modules/layout_builder/tests/src/Functional/LayoutBuilderTest.php
index c5efc3110df3..daf54a4f789c 100644
--- a/core/modules/layout_builder/tests/src/Functional/LayoutBuilderTest.php
+++ b/core/modules/layout_builder/tests/src/Functional/LayoutBuilderTest.php
@@ -29,6 +29,11 @@ class LayoutBuilderTest extends BrowserTestBase {
     'layout_builder_test',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/layout_builder/tests/src/Functional/LayoutBuilderTranslationTest.php b/core/modules/layout_builder/tests/src/Functional/LayoutBuilderTranslationTest.php
index a86388277e33..0a0d5bedcd89 100644
--- a/core/modules/layout_builder/tests/src/Functional/LayoutBuilderTranslationTest.php
+++ b/core/modules/layout_builder/tests/src/Functional/LayoutBuilderTranslationTest.php
@@ -24,6 +24,11 @@ class LayoutBuilderTranslationTest extends ContentTranslationTestBase {
     'block',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The entity used for testing.
    *
diff --git a/core/modules/layout_builder/tests/src/Functional/LayoutDisplayTest.php b/core/modules/layout_builder/tests/src/Functional/LayoutDisplayTest.php
index d1c4ba0ff6ac..a697b61e1d39 100644
--- a/core/modules/layout_builder/tests/src/Functional/LayoutDisplayTest.php
+++ b/core/modules/layout_builder/tests/src/Functional/LayoutDisplayTest.php
@@ -16,6 +16,11 @@ class LayoutDisplayTest extends BrowserTestBase {
    */
   protected static $modules = ['field_ui', 'layout_builder', 'block', 'node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/layout_builder/tests/src/Functional/LayoutSectionTest.php b/core/modules/layout_builder/tests/src/Functional/LayoutSectionTest.php
index 86ae521b1044..dc7956238d53 100644
--- a/core/modules/layout_builder/tests/src/Functional/LayoutSectionTest.php
+++ b/core/modules/layout_builder/tests/src/Functional/LayoutSectionTest.php
@@ -20,6 +20,11 @@ class LayoutSectionTest extends BrowserTestBase {
    */
   public static $modules = ['field_ui', 'layout_builder', 'node', 'block_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/layout_builder/tests/src/Functional/Rest/LayoutBuilderEntityViewDisplayJsonAnonTest.php b/core/modules/layout_builder/tests/src/Functional/Rest/LayoutBuilderEntityViewDisplayJsonAnonTest.php
index 61fa91eff913..316c1f891615 100644
--- a/core/modules/layout_builder/tests/src/Functional/Rest/LayoutBuilderEntityViewDisplayJsonAnonTest.php
+++ b/core/modules/layout_builder/tests/src/Functional/Rest/LayoutBuilderEntityViewDisplayJsonAnonTest.php
@@ -22,4 +22,9 @@ class LayoutBuilderEntityViewDisplayJsonAnonTest extends LayoutBuilderEntityView
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/layout_builder/tests/src/Functional/Rest/LayoutBuilderEntityViewDisplayJsonBasicAuthTest.php b/core/modules/layout_builder/tests/src/Functional/Rest/LayoutBuilderEntityViewDisplayJsonBasicAuthTest.php
index d92138f98463..74fba46e5b21 100644
--- a/core/modules/layout_builder/tests/src/Functional/Rest/LayoutBuilderEntityViewDisplayJsonBasicAuthTest.php
+++ b/core/modules/layout_builder/tests/src/Functional/Rest/LayoutBuilderEntityViewDisplayJsonBasicAuthTest.php
@@ -17,6 +17,11 @@ class LayoutBuilderEntityViewDisplayJsonBasicAuthTest extends LayoutBuilderEntit
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/layout_builder/tests/src/Functional/Rest/LayoutBuilderEntityViewDisplayJsonCookieTest.php b/core/modules/layout_builder/tests/src/Functional/Rest/LayoutBuilderEntityViewDisplayJsonCookieTest.php
index c96e7641b27e..de311a73257e 100644
--- a/core/modules/layout_builder/tests/src/Functional/Rest/LayoutBuilderEntityViewDisplayJsonCookieTest.php
+++ b/core/modules/layout_builder/tests/src/Functional/Rest/LayoutBuilderEntityViewDisplayJsonCookieTest.php
@@ -27,4 +27,9 @@ class LayoutBuilderEntityViewDisplayJsonCookieTest extends LayoutBuilderEntityVi
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/layout_builder/tests/src/Functional/Rest/LayoutBuilderEntityViewDisplayXmlAnonTest.php b/core/modules/layout_builder/tests/src/Functional/Rest/LayoutBuilderEntityViewDisplayXmlAnonTest.php
index 8c337c6552d5..63d3ba06634d 100644
--- a/core/modules/layout_builder/tests/src/Functional/Rest/LayoutBuilderEntityViewDisplayXmlAnonTest.php
+++ b/core/modules/layout_builder/tests/src/Functional/Rest/LayoutBuilderEntityViewDisplayXmlAnonTest.php
@@ -24,4 +24,9 @@ class LayoutBuilderEntityViewDisplayXmlAnonTest extends LayoutBuilderEntityViewD
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/layout_builder/tests/src/Functional/Rest/LayoutBuilderEntityViewDisplayXmlBasicAuthTest.php b/core/modules/layout_builder/tests/src/Functional/Rest/LayoutBuilderEntityViewDisplayXmlBasicAuthTest.php
index 6ec5880699fe..6b9b9e35d798 100644
--- a/core/modules/layout_builder/tests/src/Functional/Rest/LayoutBuilderEntityViewDisplayXmlBasicAuthTest.php
+++ b/core/modules/layout_builder/tests/src/Functional/Rest/LayoutBuilderEntityViewDisplayXmlBasicAuthTest.php
@@ -19,6 +19,11 @@ class LayoutBuilderEntityViewDisplayXmlBasicAuthTest extends LayoutBuilderEntity
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/layout_builder/tests/src/Functional/Rest/LayoutBuilderEntityViewDisplayXmlCookieTest.php b/core/modules/layout_builder/tests/src/Functional/Rest/LayoutBuilderEntityViewDisplayXmlCookieTest.php
index 92925eca90ea..fef266ca49a2 100644
--- a/core/modules/layout_builder/tests/src/Functional/Rest/LayoutBuilderEntityViewDisplayXmlCookieTest.php
+++ b/core/modules/layout_builder/tests/src/Functional/Rest/LayoutBuilderEntityViewDisplayXmlCookieTest.php
@@ -29,4 +29,9 @@ class LayoutBuilderEntityViewDisplayXmlCookieTest extends LayoutBuilderEntityVie
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/layout_builder/tests/src/Functional/Rest/OverrideSectionsTest.php b/core/modules/layout_builder/tests/src/Functional/Rest/OverrideSectionsTest.php
index 6d01a6803ce8..8549cfcbe09a 100644
--- a/core/modules/layout_builder/tests/src/Functional/Rest/OverrideSectionsTest.php
+++ b/core/modules/layout_builder/tests/src/Functional/Rest/OverrideSectionsTest.php
@@ -20,6 +20,11 @@ class OverrideSectionsTest extends LayoutRestTestBase {
    */
   protected static $resourceConfigId = 'entity.node';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/layout_builder/tests/src/FunctionalJavascript/AjaxBlockTest.php b/core/modules/layout_builder/tests/src/FunctionalJavascript/AjaxBlockTest.php
index 9cedac930e5f..99580cdef72b 100644
--- a/core/modules/layout_builder/tests/src/FunctionalJavascript/AjaxBlockTest.php
+++ b/core/modules/layout_builder/tests/src/FunctionalJavascript/AjaxBlockTest.php
@@ -23,6 +23,11 @@ class AjaxBlockTest extends WebDriverTestBase {
     'layout_builder_test',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/layout_builder/tests/src/FunctionalJavascript/BlockFilterTest.php b/core/modules/layout_builder/tests/src/FunctionalJavascript/BlockFilterTest.php
index 86912bf58e9f..14e521cc99b7 100644
--- a/core/modules/layout_builder/tests/src/FunctionalJavascript/BlockFilterTest.php
+++ b/core/modules/layout_builder/tests/src/FunctionalJavascript/BlockFilterTest.php
@@ -23,6 +23,11 @@ class BlockFilterTest extends WebDriverTestBase {
     'user',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/layout_builder/tests/src/FunctionalJavascript/BlockFormMessagesTest.php b/core/modules/layout_builder/tests/src/FunctionalJavascript/BlockFormMessagesTest.php
index 8a86fa3ecc7e..39c366ed811a 100644
--- a/core/modules/layout_builder/tests/src/FunctionalJavascript/BlockFormMessagesTest.php
+++ b/core/modules/layout_builder/tests/src/FunctionalJavascript/BlockFormMessagesTest.php
@@ -26,6 +26,11 @@ class BlockFormMessagesTest extends WebDriverTestBase {
     'contextual',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/layout_builder/tests/src/FunctionalJavascript/ContentPreviewToggleTest.php b/core/modules/layout_builder/tests/src/FunctionalJavascript/ContentPreviewToggleTest.php
index ecf96abfc123..ee5dfb1f059d 100644
--- a/core/modules/layout_builder/tests/src/FunctionalJavascript/ContentPreviewToggleTest.php
+++ b/core/modules/layout_builder/tests/src/FunctionalJavascript/ContentPreviewToggleTest.php
@@ -26,6 +26,11 @@ class ContentPreviewToggleTest extends WebDriverTestBase {
     'contextual',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/layout_builder/tests/src/FunctionalJavascript/ContextualLinksTest.php b/core/modules/layout_builder/tests/src/FunctionalJavascript/ContextualLinksTest.php
index ea0d170085c7..630b9968ce8c 100644
--- a/core/modules/layout_builder/tests/src/FunctionalJavascript/ContextualLinksTest.php
+++ b/core/modules/layout_builder/tests/src/FunctionalJavascript/ContextualLinksTest.php
@@ -28,6 +28,11 @@ class ContextualLinksTest extends WebDriverTestBase {
     'contextual',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/layout_builder/tests/src/FunctionalJavascript/FieldBlockTest.php b/core/modules/layout_builder/tests/src/FunctionalJavascript/FieldBlockTest.php
index b0b371fd45d3..bfde4f09fcdd 100644
--- a/core/modules/layout_builder/tests/src/FunctionalJavascript/FieldBlockTest.php
+++ b/core/modules/layout_builder/tests/src/FunctionalJavascript/FieldBlockTest.php
@@ -25,6 +25,11 @@ class FieldBlockTest extends WebDriverTestBase {
     'layout_builder_fieldblock_test',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/layout_builder/tests/src/FunctionalJavascript/InlineBlockPrivateFilesTest.php b/core/modules/layout_builder/tests/src/FunctionalJavascript/InlineBlockPrivateFilesTest.php
index a0c14e19a4ba..67f86e4e3690 100644
--- a/core/modules/layout_builder/tests/src/FunctionalJavascript/InlineBlockPrivateFilesTest.php
+++ b/core/modules/layout_builder/tests/src/FunctionalJavascript/InlineBlockPrivateFilesTest.php
@@ -26,6 +26,11 @@ class InlineBlockPrivateFilesTest extends InlineBlockTestBase {
     'file',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * The file system service.
    *
diff --git a/core/modules/layout_builder/tests/src/FunctionalJavascript/InlineBlockTest.php b/core/modules/layout_builder/tests/src/FunctionalJavascript/InlineBlockTest.php
index a256b2539904..a9356bacbaca 100644
--- a/core/modules/layout_builder/tests/src/FunctionalJavascript/InlineBlockTest.php
+++ b/core/modules/layout_builder/tests/src/FunctionalJavascript/InlineBlockTest.php
@@ -12,6 +12,11 @@
  */
 class InlineBlockTest extends InlineBlockTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Tests adding and editing of inline blocks.
    */
diff --git a/core/modules/layout_builder/tests/src/FunctionalJavascript/ItemLayoutFieldBlockTest.php b/core/modules/layout_builder/tests/src/FunctionalJavascript/ItemLayoutFieldBlockTest.php
index 5acc2034b3a7..73cb6ca990a9 100644
--- a/core/modules/layout_builder/tests/src/FunctionalJavascript/ItemLayoutFieldBlockTest.php
+++ b/core/modules/layout_builder/tests/src/FunctionalJavascript/ItemLayoutFieldBlockTest.php
@@ -19,6 +19,11 @@ class ItemLayoutFieldBlockTest extends WebDriverTestBase {
     'layout_builder',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/layout_builder/tests/src/FunctionalJavascript/LayoutBuilderDisableInteractionsTest.php b/core/modules/layout_builder/tests/src/FunctionalJavascript/LayoutBuilderDisableInteractionsTest.php
index 8dcd507c8dac..4445b3ac9531 100644
--- a/core/modules/layout_builder/tests/src/FunctionalJavascript/LayoutBuilderDisableInteractionsTest.php
+++ b/core/modules/layout_builder/tests/src/FunctionalJavascript/LayoutBuilderDisableInteractionsTest.php
@@ -32,6 +32,11 @@ class LayoutBuilderDisableInteractionsTest extends WebDriverTestBase {
     'contextual',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/layout_builder/tests/src/FunctionalJavascript/LayoutBuilderOptInTest.php b/core/modules/layout_builder/tests/src/FunctionalJavascript/LayoutBuilderOptInTest.php
index 03f69a770ed1..be8f70d80d16 100644
--- a/core/modules/layout_builder/tests/src/FunctionalJavascript/LayoutBuilderOptInTest.php
+++ b/core/modules/layout_builder/tests/src/FunctionalJavascript/LayoutBuilderOptInTest.php
@@ -20,6 +20,11 @@ class LayoutBuilderOptInTest extends WebDriverTestBase {
     'block',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/layout_builder/tests/src/FunctionalJavascript/LayoutBuilderQuickEditTest.php b/core/modules/layout_builder/tests/src/FunctionalJavascript/LayoutBuilderQuickEditTest.php
index 0f85fcc5b489..3c5fd56ffacb 100644
--- a/core/modules/layout_builder/tests/src/FunctionalJavascript/LayoutBuilderQuickEditTest.php
+++ b/core/modules/layout_builder/tests/src/FunctionalJavascript/LayoutBuilderQuickEditTest.php
@@ -28,6 +28,11 @@ class LayoutBuilderQuickEditTest extends QuickEditJavascriptTestBase {
     'layout_builder',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * The article node under test.
    *
diff --git a/core/modules/layout_builder/tests/src/FunctionalJavascript/LayoutBuilderTest.php b/core/modules/layout_builder/tests/src/FunctionalJavascript/LayoutBuilderTest.php
index fa274bc119a5..f92195c9dc94 100644
--- a/core/modules/layout_builder/tests/src/FunctionalJavascript/LayoutBuilderTest.php
+++ b/core/modules/layout_builder/tests/src/FunctionalJavascript/LayoutBuilderTest.php
@@ -29,6 +29,11 @@ class LayoutBuilderTest extends WebDriverTestBase {
     'node',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * The node to customize with Layout Builder.
    *
diff --git a/core/modules/layout_builder/tests/src/FunctionalJavascript/LayoutBuilderToolbarTest.php b/core/modules/layout_builder/tests/src/FunctionalJavascript/LayoutBuilderToolbarTest.php
index f1f61596a2d0..de54949efc21 100644
--- a/core/modules/layout_builder/tests/src/FunctionalJavascript/LayoutBuilderToolbarTest.php
+++ b/core/modules/layout_builder/tests/src/FunctionalJavascript/LayoutBuilderToolbarTest.php
@@ -22,6 +22,11 @@ class LayoutBuilderToolbarTest extends WebDriverTestBase {
     'toolbar',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/layout_builder/tests/src/FunctionalJavascript/LayoutBuilderUiTest.php b/core/modules/layout_builder/tests/src/FunctionalJavascript/LayoutBuilderUiTest.php
index 5ec449b28a9a..85cb669f4214 100644
--- a/core/modules/layout_builder/tests/src/FunctionalJavascript/LayoutBuilderUiTest.php
+++ b/core/modules/layout_builder/tests/src/FunctionalJavascript/LayoutBuilderUiTest.php
@@ -31,6 +31,11 @@ class LayoutBuilderUiTest extends WebDriverTestBase {
     'views',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/layout_builder/tests/src/FunctionalJavascript/MoveBlockFormTest.php b/core/modules/layout_builder/tests/src/FunctionalJavascript/MoveBlockFormTest.php
index e8cf15f4074b..7ceb0af8da78 100644
--- a/core/modules/layout_builder/tests/src/FunctionalJavascript/MoveBlockFormTest.php
+++ b/core/modules/layout_builder/tests/src/FunctionalJavascript/MoveBlockFormTest.php
@@ -31,6 +31,11 @@ class MoveBlockFormTest extends WebDriverTestBase {
     'contextual',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/layout_builder/tests/src/FunctionalJavascript/TestMultiWidthLayoutsTest.php b/core/modules/layout_builder/tests/src/FunctionalJavascript/TestMultiWidthLayoutsTest.php
index 86edc44efdfb..0049edc1e074 100644
--- a/core/modules/layout_builder/tests/src/FunctionalJavascript/TestMultiWidthLayoutsTest.php
+++ b/core/modules/layout_builder/tests/src/FunctionalJavascript/TestMultiWidthLayoutsTest.php
@@ -24,6 +24,11 @@ class TestMultiWidthLayoutsTest extends WebDriverTestBase {
     'node',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/link/tests/src/Functional/LinkFieldTest.php b/core/modules/link/tests/src/Functional/LinkFieldTest.php
index fb3680af66fc..fda83fd5646e 100644
--- a/core/modules/link/tests/src/Functional/LinkFieldTest.php
+++ b/core/modules/link/tests/src/Functional/LinkFieldTest.php
@@ -36,6 +36,11 @@ class LinkFieldTest extends BrowserTestBase {
     'link_test_base_field',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * A field to use in this test class.
    *
diff --git a/core/modules/link/tests/src/Functional/LinkFieldUITest.php b/core/modules/link/tests/src/Functional/LinkFieldUITest.php
index 276877066522..65e4125dc38e 100644
--- a/core/modules/link/tests/src/Functional/LinkFieldUITest.php
+++ b/core/modules/link/tests/src/Functional/LinkFieldUITest.php
@@ -27,6 +27,11 @@ class LinkFieldUITest extends BrowserTestBase {
    */
   public static $modules = ['node', 'link', 'field_ui', 'block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * A user that can edit content types.
    *
diff --git a/core/modules/link/tests/src/Functional/Views/LinkViewsTokensTest.php b/core/modules/link/tests/src/Functional/Views/LinkViewsTokensTest.php
index b1cce75d0e3a..4b9f0e932a9b 100644
--- a/core/modules/link/tests/src/Functional/Views/LinkViewsTokensTest.php
+++ b/core/modules/link/tests/src/Functional/Views/LinkViewsTokensTest.php
@@ -21,6 +21,11 @@ class LinkViewsTokensTest extends ViewTestBase {
    */
   public static $modules = ['link_test_views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/locale/tests/src/Functional/LocaleConfigTranslationImportTest.php b/core/modules/locale/tests/src/Functional/LocaleConfigTranslationImportTest.php
index 058d9ddf8e77..64dcb705d8a6 100644
--- a/core/modules/locale/tests/src/Functional/LocaleConfigTranslationImportTest.php
+++ b/core/modules/locale/tests/src/Functional/LocaleConfigTranslationImportTest.php
@@ -20,6 +20,11 @@ class LocaleConfigTranslationImportTest extends BrowserTestBase {
    */
   public static $modules = ['language', 'locale_test_translate'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/locale/tests/src/Functional/LocaleConfigTranslationTest.php b/core/modules/locale/tests/src/Functional/LocaleConfigTranslationTest.php
index f3217691d62a..bc1d914c1c6d 100644
--- a/core/modules/locale/tests/src/Functional/LocaleConfigTranslationTest.php
+++ b/core/modules/locale/tests/src/Functional/LocaleConfigTranslationTest.php
@@ -26,6 +26,11 @@ class LocaleConfigTranslationTest extends BrowserTestBase {
    */
   public static $modules = ['locale', 'contact', 'contact_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/locale/tests/src/Functional/LocaleContentTest.php b/core/modules/locale/tests/src/Functional/LocaleContentTest.php
index e7955503a437..9ac40754f807 100644
--- a/core/modules/locale/tests/src/Functional/LocaleContentTest.php
+++ b/core/modules/locale/tests/src/Functional/LocaleContentTest.php
@@ -21,6 +21,11 @@ class LocaleContentTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'locale'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Verifies that machine name fields are always LTR.
    */
diff --git a/core/modules/locale/tests/src/Functional/LocaleExportTest.php b/core/modules/locale/tests/src/Functional/LocaleExportTest.php
index 1b0d67e88af8..9869fb70a222 100644
--- a/core/modules/locale/tests/src/Functional/LocaleExportTest.php
+++ b/core/modules/locale/tests/src/Functional/LocaleExportTest.php
@@ -19,6 +19,11 @@ class LocaleExportTest extends BrowserTestBase {
    */
   public static $modules = ['locale'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user able to create languages and export translations.
    */
diff --git a/core/modules/locale/tests/src/Functional/LocaleFileSystemFormTest.php b/core/modules/locale/tests/src/Functional/LocaleFileSystemFormTest.php
index c38da43d77fc..6a866af5115a 100644
--- a/core/modules/locale/tests/src/Functional/LocaleFileSystemFormTest.php
+++ b/core/modules/locale/tests/src/Functional/LocaleFileSystemFormTest.php
@@ -18,6 +18,11 @@ class LocaleFileSystemFormTest extends BrowserTestBase {
    */
   public static $modules = ['system'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/locale/tests/src/Functional/LocaleImportFunctionalTest.php b/core/modules/locale/tests/src/Functional/LocaleImportFunctionalTest.php
index 1005c5c2342c..11906f3893f1 100644
--- a/core/modules/locale/tests/src/Functional/LocaleImportFunctionalTest.php
+++ b/core/modules/locale/tests/src/Functional/LocaleImportFunctionalTest.php
@@ -23,6 +23,11 @@ class LocaleImportFunctionalTest extends BrowserTestBase {
    */
   public static $modules = ['locale', 'dblog'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user able to create languages and import translations.
    *
diff --git a/core/modules/locale/tests/src/Functional/LocaleJavascriptTranslationTest.php b/core/modules/locale/tests/src/Functional/LocaleJavascriptTranslationTest.php
index 2219fa46640a..62036cd8bbdc 100644
--- a/core/modules/locale/tests/src/Functional/LocaleJavascriptTranslationTest.php
+++ b/core/modules/locale/tests/src/Functional/LocaleJavascriptTranslationTest.php
@@ -21,6 +21,11 @@ class LocaleJavascriptTranslationTest extends BrowserTestBase {
    */
   public static $modules = ['locale', 'locale_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   public function testFileParsing() {
 
     // This test is for ensuring that the regular expression in
diff --git a/core/modules/locale/tests/src/Functional/LocaleLocaleLookupTest.php b/core/modules/locale/tests/src/Functional/LocaleLocaleLookupTest.php
index 3dd4eadb58da..02edcb7676e0 100644
--- a/core/modules/locale/tests/src/Functional/LocaleLocaleLookupTest.php
+++ b/core/modules/locale/tests/src/Functional/LocaleLocaleLookupTest.php
@@ -20,6 +20,11 @@ class LocaleLocaleLookupTest extends BrowserTestBase {
    */
   public static $modules = ['locale', 'locale_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/locale/tests/src/Functional/LocaleNonInteractiveDevInstallTest.php b/core/modules/locale/tests/src/Functional/LocaleNonInteractiveDevInstallTest.php
index 080616af91ca..6798f5a9aa19 100644
--- a/core/modules/locale/tests/src/Functional/LocaleNonInteractiveDevInstallTest.php
+++ b/core/modules/locale/tests/src/Functional/LocaleNonInteractiveDevInstallTest.php
@@ -9,6 +9,11 @@
  */
 class LocaleNonInteractiveDevInstallTest extends LocaleNonInteractiveInstallTest {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/locale/tests/src/Functional/LocaleNonInteractiveInstallTest.php b/core/modules/locale/tests/src/Functional/LocaleNonInteractiveInstallTest.php
index ee12a6713ae3..ea3c1b5aba1f 100644
--- a/core/modules/locale/tests/src/Functional/LocaleNonInteractiveInstallTest.php
+++ b/core/modules/locale/tests/src/Functional/LocaleNonInteractiveInstallTest.php
@@ -11,6 +11,11 @@
  */
 class LocaleNonInteractiveInstallTest extends BrowserTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Gets the version string to use in the translation file.
    *
diff --git a/core/modules/locale/tests/src/Functional/LocalePathTest.php b/core/modules/locale/tests/src/Functional/LocalePathTest.php
index 588488eb0b2e..9b1584e44682 100644
--- a/core/modules/locale/tests/src/Functional/LocalePathTest.php
+++ b/core/modules/locale/tests/src/Functional/LocalePathTest.php
@@ -24,6 +24,11 @@ class LocalePathTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'locale', 'path', 'views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/locale/tests/src/Functional/LocalePluralFormatTest.php b/core/modules/locale/tests/src/Functional/LocalePluralFormatTest.php
index 0b2a88caed25..b85e737a06bb 100644
--- a/core/modules/locale/tests/src/Functional/LocalePluralFormatTest.php
+++ b/core/modules/locale/tests/src/Functional/LocalePluralFormatTest.php
@@ -28,6 +28,11 @@ class LocalePluralFormatTest extends BrowserTestBase {
    */
   public static $modules = ['locale'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/locale/tests/src/Functional/LocaleTranslateStringTourTest.php b/core/modules/locale/tests/src/Functional/LocaleTranslateStringTourTest.php
index ffd5bc7b02f2..19db1b38ed2b 100644
--- a/core/modules/locale/tests/src/Functional/LocaleTranslateStringTourTest.php
+++ b/core/modules/locale/tests/src/Functional/LocaleTranslateStringTourTest.php
@@ -25,6 +25,11 @@ class LocaleTranslateStringTourTest extends TourTestBase {
    */
   public static $modules = ['locale', 'tour'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/locale/tests/src/Functional/LocaleTranslatedSchemaDefinitionTest.php b/core/modules/locale/tests/src/Functional/LocaleTranslatedSchemaDefinitionTest.php
index 6f292693f828..71186fa0c3e9 100644
--- a/core/modules/locale/tests/src/Functional/LocaleTranslatedSchemaDefinitionTest.php
+++ b/core/modules/locale/tests/src/Functional/LocaleTranslatedSchemaDefinitionTest.php
@@ -22,6 +22,11 @@ class LocaleTranslatedSchemaDefinitionTest extends BrowserTestBase {
    */
   public static $modules = ['language', 'locale', 'node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/locale/tests/src/Functional/LocaleTranslationDownloadTest.php b/core/modules/locale/tests/src/Functional/LocaleTranslationDownloadTest.php
index f97a8d607cfd..7b727518a84a 100644
--- a/core/modules/locale/tests/src/Functional/LocaleTranslationDownloadTest.php
+++ b/core/modules/locale/tests/src/Functional/LocaleTranslationDownloadTest.php
@@ -20,6 +20,11 @@ class LocaleTranslationDownloadTest extends LocaleUpdateBase {
    */
   protected $translationsStream;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/locale/tests/src/Functional/LocaleTranslationUiTest.php b/core/modules/locale/tests/src/Functional/LocaleTranslationUiTest.php
index d9aa561d6b37..f8fe9c6db1c3 100644
--- a/core/modules/locale/tests/src/Functional/LocaleTranslationUiTest.php
+++ b/core/modules/locale/tests/src/Functional/LocaleTranslationUiTest.php
@@ -24,6 +24,11 @@ class LocaleTranslationUiTest extends BrowserTestBase {
    */
   public static $modules = ['locale'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Enable interface translation to English.
    */
diff --git a/core/modules/locale/tests/src/Functional/LocaleUpdateCronTest.php b/core/modules/locale/tests/src/Functional/LocaleUpdateCronTest.php
index dd167439fa40..34ee9dc36a8a 100644
--- a/core/modules/locale/tests/src/Functional/LocaleUpdateCronTest.php
+++ b/core/modules/locale/tests/src/Functional/LocaleUpdateCronTest.php
@@ -16,6 +16,11 @@ class LocaleUpdateCronTest extends LocaleUpdateBase {
 
   protected $batchOutput = [];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/locale/tests/src/Functional/LocaleUpdateDevelopmentReleaseTest.php b/core/modules/locale/tests/src/Functional/LocaleUpdateDevelopmentReleaseTest.php
index 5c972d1ef377..592119840793 100644
--- a/core/modules/locale/tests/src/Functional/LocaleUpdateDevelopmentReleaseTest.php
+++ b/core/modules/locale/tests/src/Functional/LocaleUpdateDevelopmentReleaseTest.php
@@ -13,6 +13,11 @@ class LocaleUpdateDevelopmentReleaseTest extends BrowserTestBase {
 
   public static $modules = ['locale', 'locale_test_development_release'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     module_load_include('compare.inc', 'locale');
diff --git a/core/modules/locale/tests/src/Functional/LocaleUpdateInterfaceTest.php b/core/modules/locale/tests/src/Functional/LocaleUpdateInterfaceTest.php
index dcf1ba08c44c..5c7d698f4240 100644
--- a/core/modules/locale/tests/src/Functional/LocaleUpdateInterfaceTest.php
+++ b/core/modules/locale/tests/src/Functional/LocaleUpdateInterfaceTest.php
@@ -19,6 +19,11 @@ class LocaleUpdateInterfaceTest extends LocaleUpdateBase {
    */
   public static $modules = ['locale_test_translate'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/locale/tests/src/Functional/LocaleUpdateTest.php b/core/modules/locale/tests/src/Functional/LocaleUpdateTest.php
index e7210dc6eed2..2c25228d10ef 100644
--- a/core/modules/locale/tests/src/Functional/LocaleUpdateTest.php
+++ b/core/modules/locale/tests/src/Functional/LocaleUpdateTest.php
@@ -12,6 +12,11 @@
  */
 class LocaleUpdateTest extends LocaleUpdateBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/media/tests/src/Functional/FieldFormatter/OEmbedFormatterTest.php b/core/modules/media/tests/src/Functional/FieldFormatter/OEmbedFormatterTest.php
index 2a0a0959586d..b4e576761496 100644
--- a/core/modules/media/tests/src/Functional/FieldFormatter/OEmbedFormatterTest.php
+++ b/core/modules/media/tests/src/Functional/FieldFormatter/OEmbedFormatterTest.php
@@ -27,6 +27,11 @@ class OEmbedFormatterTest extends MediaFunctionalTestBase {
     'media_test_oembed',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/media/tests/src/Functional/Hal/MediaHalJsonAnonTest.php b/core/modules/media/tests/src/Functional/Hal/MediaHalJsonAnonTest.php
index 2b92c73be2ff..6f990b6641d1 100644
--- a/core/modules/media/tests/src/Functional/Hal/MediaHalJsonAnonTest.php
+++ b/core/modules/media/tests/src/Functional/Hal/MediaHalJsonAnonTest.php
@@ -22,6 +22,11 @@ class MediaHalJsonAnonTest extends MediaResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/media/tests/src/Functional/Hal/MediaHalJsonBasicAuthTest.php b/core/modules/media/tests/src/Functional/Hal/MediaHalJsonBasicAuthTest.php
index 73d37b377e00..92019bf75f5a 100644
--- a/core/modules/media/tests/src/Functional/Hal/MediaHalJsonBasicAuthTest.php
+++ b/core/modules/media/tests/src/Functional/Hal/MediaHalJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class MediaHalJsonBasicAuthTest extends MediaHalJsonAnonTest {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/media/tests/src/Functional/Hal/MediaHalJsonCookieTest.php b/core/modules/media/tests/src/Functional/Hal/MediaHalJsonCookieTest.php
index 798cf39a21c6..16a76ec71b2e 100644
--- a/core/modules/media/tests/src/Functional/Hal/MediaHalJsonCookieTest.php
+++ b/core/modules/media/tests/src/Functional/Hal/MediaHalJsonCookieTest.php
@@ -16,4 +16,9 @@ class MediaHalJsonCookieTest extends MediaHalJsonAnonTest {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/media/tests/src/Functional/Hal/MediaTypeHalJsonAnonTest.php b/core/modules/media/tests/src/Functional/Hal/MediaTypeHalJsonAnonTest.php
index 6a5611f9c781..4618e492c0af 100644
--- a/core/modules/media/tests/src/Functional/Hal/MediaTypeHalJsonAnonTest.php
+++ b/core/modules/media/tests/src/Functional/Hal/MediaTypeHalJsonAnonTest.php
@@ -17,6 +17,11 @@ class MediaTypeHalJsonAnonTest extends MediaTypeResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/media/tests/src/Functional/Hal/MediaTypeHalJsonBasicAuthTest.php b/core/modules/media/tests/src/Functional/Hal/MediaTypeHalJsonBasicAuthTest.php
index 0ef13e995243..3fc0aaba1337 100644
--- a/core/modules/media/tests/src/Functional/Hal/MediaTypeHalJsonBasicAuthTest.php
+++ b/core/modules/media/tests/src/Functional/Hal/MediaTypeHalJsonBasicAuthTest.php
@@ -17,6 +17,11 @@ class MediaTypeHalJsonBasicAuthTest extends MediaTypeResourceTestBase {
    */
   public static $modules = ['hal', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/media/tests/src/Functional/Hal/MediaTypeHalJsonCookieTest.php b/core/modules/media/tests/src/Functional/Hal/MediaTypeHalJsonCookieTest.php
index c66b499ef5b3..62de7a48b143 100644
--- a/core/modules/media/tests/src/Functional/Hal/MediaTypeHalJsonCookieTest.php
+++ b/core/modules/media/tests/src/Functional/Hal/MediaTypeHalJsonCookieTest.php
@@ -17,6 +17,11 @@ class MediaTypeHalJsonCookieTest extends MediaTypeResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/media/tests/src/Functional/MediaAccessTest.php b/core/modules/media/tests/src/Functional/MediaAccessTest.php
index 050c567da84a..c50f573300f5 100644
--- a/core/modules/media/tests/src/Functional/MediaAccessTest.php
+++ b/core/modules/media/tests/src/Functional/MediaAccessTest.php
@@ -26,6 +26,11 @@ class MediaAccessTest extends MediaFunctionalTestBase {
     'media_test_source',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/media/tests/src/Functional/MediaBulkFormTest.php b/core/modules/media/tests/src/Functional/MediaBulkFormTest.php
index fb9caf1fdd79..5bb70a2a82a0 100644
--- a/core/modules/media/tests/src/Functional/MediaBulkFormTest.php
+++ b/core/modules/media/tests/src/Functional/MediaBulkFormTest.php
@@ -19,6 +19,11 @@ class MediaBulkFormTest extends MediaFunctionalTestBase {
    */
   public static $modules = ['media_test_views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The test media type.
    *
diff --git a/core/modules/media/tests/src/Functional/MediaCacheTagsTest.php b/core/modules/media/tests/src/Functional/MediaCacheTagsTest.php
index a2c3530abcc1..eb3402fc88cd 100644
--- a/core/modules/media/tests/src/Functional/MediaCacheTagsTest.php
+++ b/core/modules/media/tests/src/Functional/MediaCacheTagsTest.php
@@ -24,6 +24,11 @@ class MediaCacheTagsTest extends EntityWithUriCacheTagsTestBase {
     'media_test_source',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/media/tests/src/Functional/MediaContextualLinksTest.php b/core/modules/media/tests/src/Functional/MediaContextualLinksTest.php
index 5eeaa95ce8c6..35c1224c7ed2 100644
--- a/core/modules/media/tests/src/Functional/MediaContextualLinksTest.php
+++ b/core/modules/media/tests/src/Functional/MediaContextualLinksTest.php
@@ -18,6 +18,11 @@ class MediaContextualLinksTest extends MediaFunctionalTestBase {
     'contextual',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests contextual links.
    */
diff --git a/core/modules/media/tests/src/Functional/MediaInstallTest.php b/core/modules/media/tests/src/Functional/MediaInstallTest.php
index 010f07698a94..0811322fb9df 100644
--- a/core/modules/media/tests/src/Functional/MediaInstallTest.php
+++ b/core/modules/media/tests/src/Functional/MediaInstallTest.php
@@ -16,6 +16,11 @@ class MediaInstallTest extends BrowserTestBase {
    */
   public static $modules = ['media'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/media/tests/src/Functional/MediaOverviewPageTest.php b/core/modules/media/tests/src/Functional/MediaOverviewPageTest.php
index f1d574a17ac8..d4f82eaea023 100644
--- a/core/modules/media/tests/src/Functional/MediaOverviewPageTest.php
+++ b/core/modules/media/tests/src/Functional/MediaOverviewPageTest.php
@@ -13,6 +13,11 @@
  */
 class MediaOverviewPageTest extends MediaFunctionalTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/media/tests/src/Functional/MediaRevisionTest.php b/core/modules/media/tests/src/Functional/MediaRevisionTest.php
index 75638aeec0a6..6ec57bea2cb9 100644
--- a/core/modules/media/tests/src/Functional/MediaRevisionTest.php
+++ b/core/modules/media/tests/src/Functional/MediaRevisionTest.php
@@ -15,6 +15,11 @@
  */
 class MediaRevisionTest extends MediaFunctionalTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Checks media revision operations.
    */
diff --git a/core/modules/media/tests/src/Functional/MediaSettingsTest.php b/core/modules/media/tests/src/Functional/MediaSettingsTest.php
index ba25392f5c6b..0a5a00b2f436 100644
--- a/core/modules/media/tests/src/Functional/MediaSettingsTest.php
+++ b/core/modules/media/tests/src/Functional/MediaSettingsTest.php
@@ -9,6 +9,11 @@
  */
 class MediaSettingsTest extends MediaFunctionalTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/media/tests/src/Functional/MediaSourceFileTest.php b/core/modules/media/tests/src/Functional/MediaSourceFileTest.php
index fad13dc81f04..55fb9276f321 100644
--- a/core/modules/media/tests/src/Functional/MediaSourceFileTest.php
+++ b/core/modules/media/tests/src/Functional/MediaSourceFileTest.php
@@ -11,6 +11,11 @@
  */
 class MediaSourceFileTest extends MediaFunctionalTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test that it's possible to change the allowed file extensions.
    */
diff --git a/core/modules/media/tests/src/Functional/MediaTemplateSuggestionsTest.php b/core/modules/media/tests/src/Functional/MediaTemplateSuggestionsTest.php
index 916eb7cfc207..eef7ae34cd63 100644
--- a/core/modules/media/tests/src/Functional/MediaTemplateSuggestionsTest.php
+++ b/core/modules/media/tests/src/Functional/MediaTemplateSuggestionsTest.php
@@ -18,6 +18,11 @@ class MediaTemplateSuggestionsTest extends MediaFunctionalTestBase {
    */
   public static $modules = ['media'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests template suggestions from media_theme_suggestions_media().
    */
diff --git a/core/modules/media/tests/src/Functional/MediaTranslationUITest.php b/core/modules/media/tests/src/Functional/MediaTranslationUITest.php
index 167d76a30ba1..9ac587a5d045 100644
--- a/core/modules/media/tests/src/Functional/MediaTranslationUITest.php
+++ b/core/modules/media/tests/src/Functional/MediaTranslationUITest.php
@@ -14,6 +14,11 @@ class MediaTranslationUITest extends ContentTranslationUITestBase {
 
   use MediaTypeCreationTrait;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {inheritdoc}
    */
diff --git a/core/modules/media/tests/src/Functional/MediaTypeCreationTest.php b/core/modules/media/tests/src/Functional/MediaTypeCreationTest.php
index 7de1cd8276d9..2ced87cf459f 100644
--- a/core/modules/media/tests/src/Functional/MediaTypeCreationTest.php
+++ b/core/modules/media/tests/src/Functional/MediaTypeCreationTest.php
@@ -18,6 +18,11 @@ class MediaTypeCreationTest extends MediaFunctionalTestBase {
     'media_test_source',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the media type creation form with only the mandatory options.
    */
diff --git a/core/modules/media/tests/src/Functional/MediaUiFunctionalTest.php b/core/modules/media/tests/src/Functional/MediaUiFunctionalTest.php
index 130baa41626c..dacd9e9fe8d5 100644
--- a/core/modules/media/tests/src/Functional/MediaUiFunctionalTest.php
+++ b/core/modules/media/tests/src/Functional/MediaUiFunctionalTest.php
@@ -25,6 +25,11 @@ class MediaUiFunctionalTest extends MediaFunctionalTestBase {
     'media_test_source',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/media/tests/src/Functional/ProviderRepositoryTest.php b/core/modules/media/tests/src/Functional/ProviderRepositoryTest.php
index d04d46f91c69..8c583e4ba5a6 100644
--- a/core/modules/media/tests/src/Functional/ProviderRepositoryTest.php
+++ b/core/modules/media/tests/src/Functional/ProviderRepositoryTest.php
@@ -13,6 +13,11 @@
  */
 class ProviderRepositoryTest extends MediaFunctionalTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that provider discovery fails if the provider database is empty.
    *
diff --git a/core/modules/media/tests/src/Functional/ResourceFetcherTest.php b/core/modules/media/tests/src/Functional/ResourceFetcherTest.php
index e10ef2e20939..7aed9b062d34 100644
--- a/core/modules/media/tests/src/Functional/ResourceFetcherTest.php
+++ b/core/modules/media/tests/src/Functional/ResourceFetcherTest.php
@@ -16,6 +16,11 @@ class ResourceFetcherTest extends MediaFunctionalTestBase {
 
   use OEmbedTestTrait;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/media/tests/src/Functional/Rest/MediaJsonAnonTest.php b/core/modules/media/tests/src/Functional/Rest/MediaJsonAnonTest.php
index 0aae16a00d7e..2576c5551d57 100644
--- a/core/modules/media/tests/src/Functional/Rest/MediaJsonAnonTest.php
+++ b/core/modules/media/tests/src/Functional/Rest/MediaJsonAnonTest.php
@@ -21,4 +21,9 @@ class MediaJsonAnonTest extends MediaResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/media/tests/src/Functional/Rest/MediaJsonBasicAuthTest.php b/core/modules/media/tests/src/Functional/Rest/MediaJsonBasicAuthTest.php
index b124487d4277..c65a3b2fd6f3 100644
--- a/core/modules/media/tests/src/Functional/Rest/MediaJsonBasicAuthTest.php
+++ b/core/modules/media/tests/src/Functional/Rest/MediaJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class MediaJsonBasicAuthTest extends MediaResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/media/tests/src/Functional/Rest/MediaJsonCookieTest.php b/core/modules/media/tests/src/Functional/Rest/MediaJsonCookieTest.php
index 9c6786f1340a..09dd245027b4 100644
--- a/core/modules/media/tests/src/Functional/Rest/MediaJsonCookieTest.php
+++ b/core/modules/media/tests/src/Functional/Rest/MediaJsonCookieTest.php
@@ -26,4 +26,9 @@ class MediaJsonCookieTest extends MediaResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/media/tests/src/Functional/Rest/MediaTypeJsonAnonTest.php b/core/modules/media/tests/src/Functional/Rest/MediaTypeJsonAnonTest.php
index 6ee494de5296..0f5066898143 100644
--- a/core/modules/media/tests/src/Functional/Rest/MediaTypeJsonAnonTest.php
+++ b/core/modules/media/tests/src/Functional/Rest/MediaTypeJsonAnonTest.php
@@ -21,4 +21,9 @@ class MediaTypeJsonAnonTest extends MediaTypeResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/media/tests/src/Functional/Rest/MediaTypeJsonBasicAuthTest.php b/core/modules/media/tests/src/Functional/Rest/MediaTypeJsonBasicAuthTest.php
index 84b1a01c87ad..640ad42ef00d 100644
--- a/core/modules/media/tests/src/Functional/Rest/MediaTypeJsonBasicAuthTest.php
+++ b/core/modules/media/tests/src/Functional/Rest/MediaTypeJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class MediaTypeJsonBasicAuthTest extends MediaTypeResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/media/tests/src/Functional/Rest/MediaTypeJsonCookieTest.php b/core/modules/media/tests/src/Functional/Rest/MediaTypeJsonCookieTest.php
index 90c27b2d519e..9a3d459dec27 100644
--- a/core/modules/media/tests/src/Functional/Rest/MediaTypeJsonCookieTest.php
+++ b/core/modules/media/tests/src/Functional/Rest/MediaTypeJsonCookieTest.php
@@ -26,4 +26,9 @@ class MediaTypeJsonCookieTest extends MediaTypeResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/media/tests/src/Functional/Rest/MediaTypeXmlAnonTest.php b/core/modules/media/tests/src/Functional/Rest/MediaTypeXmlAnonTest.php
index 083d80a1c1e1..cd6bc82c45be 100644
--- a/core/modules/media/tests/src/Functional/Rest/MediaTypeXmlAnonTest.php
+++ b/core/modules/media/tests/src/Functional/Rest/MediaTypeXmlAnonTest.php
@@ -23,4 +23,9 @@ class MediaTypeXmlAnonTest extends MediaTypeResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/media/tests/src/Functional/Rest/MediaTypeXmlBasicAuthTest.php b/core/modules/media/tests/src/Functional/Rest/MediaTypeXmlBasicAuthTest.php
index 95de21197dc8..6bd780977235 100644
--- a/core/modules/media/tests/src/Functional/Rest/MediaTypeXmlBasicAuthTest.php
+++ b/core/modules/media/tests/src/Functional/Rest/MediaTypeXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class MediaTypeXmlBasicAuthTest extends MediaTypeResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/media/tests/src/Functional/Rest/MediaTypeXmlCookieTest.php b/core/modules/media/tests/src/Functional/Rest/MediaTypeXmlCookieTest.php
index 3b6a53d96ff0..c28c72311a52 100644
--- a/core/modules/media/tests/src/Functional/Rest/MediaTypeXmlCookieTest.php
+++ b/core/modules/media/tests/src/Functional/Rest/MediaTypeXmlCookieTest.php
@@ -28,4 +28,9 @@ class MediaTypeXmlCookieTest extends MediaTypeResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/media/tests/src/Functional/Rest/MediaXmlAnonTest.php b/core/modules/media/tests/src/Functional/Rest/MediaXmlAnonTest.php
index 787794996ace..baafbcb3d262 100644
--- a/core/modules/media/tests/src/Functional/Rest/MediaXmlAnonTest.php
+++ b/core/modules/media/tests/src/Functional/Rest/MediaXmlAnonTest.php
@@ -23,4 +23,9 @@ class MediaXmlAnonTest extends MediaResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/media/tests/src/Functional/Rest/MediaXmlBasicAuthTest.php b/core/modules/media/tests/src/Functional/Rest/MediaXmlBasicAuthTest.php
index 971e75f42cad..9d41af515f92 100644
--- a/core/modules/media/tests/src/Functional/Rest/MediaXmlBasicAuthTest.php
+++ b/core/modules/media/tests/src/Functional/Rest/MediaXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class MediaXmlBasicAuthTest extends MediaResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/media/tests/src/Functional/Rest/MediaXmlCookieTest.php b/core/modules/media/tests/src/Functional/Rest/MediaXmlCookieTest.php
index f67f7b4f8c01..16a36458a942 100644
--- a/core/modules/media/tests/src/Functional/Rest/MediaXmlCookieTest.php
+++ b/core/modules/media/tests/src/Functional/Rest/MediaXmlCookieTest.php
@@ -28,4 +28,9 @@ class MediaXmlCookieTest extends MediaResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/media/tests/src/Functional/UrlResolverTest.php b/core/modules/media/tests/src/Functional/UrlResolverTest.php
index 5e4dfc35143b..5073625811c9 100644
--- a/core/modules/media/tests/src/Functional/UrlResolverTest.php
+++ b/core/modules/media/tests/src/Functional/UrlResolverTest.php
@@ -15,6 +15,11 @@ class UrlResolverTest extends MediaFunctionalTestBase {
 
   use OEmbedTestTrait;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/media/tests/src/FunctionalJavascript/CKEditorIntegrationTest.php b/core/modules/media/tests/src/FunctionalJavascript/CKEditorIntegrationTest.php
index 40e169cc6981..1a0e7201d4cd 100644
--- a/core/modules/media/tests/src/FunctionalJavascript/CKEditorIntegrationTest.php
+++ b/core/modules/media/tests/src/FunctionalJavascript/CKEditorIntegrationTest.php
@@ -75,6 +75,11 @@ class CKEditorIntegrationTest extends WebDriverTestBase {
     'media_test_ckeditor',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/media/tests/src/FunctionalJavascript/MediaDisplayTest.php b/core/modules/media/tests/src/FunctionalJavascript/MediaDisplayTest.php
index 9a150ceaea2b..9c0856670571 100644
--- a/core/modules/media/tests/src/FunctionalJavascript/MediaDisplayTest.php
+++ b/core/modules/media/tests/src/FunctionalJavascript/MediaDisplayTest.php
@@ -17,6 +17,11 @@
  */
 class MediaDisplayTest extends MediaJavascriptTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/media/tests/src/FunctionalJavascript/MediaEmbedFilterConfigurationUiTest.php b/core/modules/media/tests/src/FunctionalJavascript/MediaEmbedFilterConfigurationUiTest.php
index e3eff54025fb..46d9568848d6 100644
--- a/core/modules/media/tests/src/FunctionalJavascript/MediaEmbedFilterConfigurationUiTest.php
+++ b/core/modules/media/tests/src/FunctionalJavascript/MediaEmbedFilterConfigurationUiTest.php
@@ -10,6 +10,11 @@
  */
 class MediaEmbedFilterConfigurationUiTest extends MediaJavascriptTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/media/tests/src/FunctionalJavascript/MediaReferenceFieldHelpTest.php b/core/modules/media/tests/src/FunctionalJavascript/MediaReferenceFieldHelpTest.php
index 7c109c1db8a1..c817c790b0ad 100644
--- a/core/modules/media/tests/src/FunctionalJavascript/MediaReferenceFieldHelpTest.php
+++ b/core/modules/media/tests/src/FunctionalJavascript/MediaReferenceFieldHelpTest.php
@@ -11,6 +11,11 @@
  */
 class MediaReferenceFieldHelpTest extends MediaJavascriptTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test our custom help texts when creating a field.
    *
diff --git a/core/modules/media/tests/src/FunctionalJavascript/MediaSourceAudioVideoTest.php b/core/modules/media/tests/src/FunctionalJavascript/MediaSourceAudioVideoTest.php
index 2195f74b3443..a3223c7484d4 100644
--- a/core/modules/media/tests/src/FunctionalJavascript/MediaSourceAudioVideoTest.php
+++ b/core/modules/media/tests/src/FunctionalJavascript/MediaSourceAudioVideoTest.php
@@ -14,6 +14,11 @@
  */
 class MediaSourceAudioVideoTest extends MediaSourceTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Check the Audio source functionality.
    */
diff --git a/core/modules/media/tests/src/FunctionalJavascript/MediaSourceFileTest.php b/core/modules/media/tests/src/FunctionalJavascript/MediaSourceFileTest.php
index e77c5203cd9c..6d9c1f44bd31 100644
--- a/core/modules/media/tests/src/FunctionalJavascript/MediaSourceFileTest.php
+++ b/core/modules/media/tests/src/FunctionalJavascript/MediaSourceFileTest.php
@@ -12,6 +12,11 @@
  */
 class MediaSourceFileTest extends MediaSourceTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Tests the file media source.
    */
diff --git a/core/modules/media/tests/src/FunctionalJavascript/MediaSourceImageTest.php b/core/modules/media/tests/src/FunctionalJavascript/MediaSourceImageTest.php
index 3b485757e27f..19233736cced 100644
--- a/core/modules/media/tests/src/FunctionalJavascript/MediaSourceImageTest.php
+++ b/core/modules/media/tests/src/FunctionalJavascript/MediaSourceImageTest.php
@@ -18,6 +18,11 @@
  */
 class MediaSourceImageTest extends MediaSourceTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Tests the image media source.
    */
diff --git a/core/modules/media/tests/src/FunctionalJavascript/MediaSourceOEmbedVideoTest.php b/core/modules/media/tests/src/FunctionalJavascript/MediaSourceOEmbedVideoTest.php
index 91f47ca74dc4..423727136629 100644
--- a/core/modules/media/tests/src/FunctionalJavascript/MediaSourceOEmbedVideoTest.php
+++ b/core/modules/media/tests/src/FunctionalJavascript/MediaSourceOEmbedVideoTest.php
@@ -21,6 +21,11 @@ class MediaSourceOEmbedVideoTest extends MediaSourceTestBase {
    */
   public static $modules = ['media_test_oembed'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   use OEmbedTestTrait;
 
   /**
diff --git a/core/modules/media/tests/src/FunctionalJavascript/MediaStandardProfileTest.php b/core/modules/media/tests/src/FunctionalJavascript/MediaStandardProfileTest.php
index b7ddb9ed7e47..0453460ba517 100644
--- a/core/modules/media/tests/src/FunctionalJavascript/MediaStandardProfileTest.php
+++ b/core/modules/media/tests/src/FunctionalJavascript/MediaStandardProfileTest.php
@@ -28,6 +28,11 @@ class MediaStandardProfileTest extends MediaJavascriptTestBase {
    */
   public static $modules = ['media_test_oembed'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/media/tests/src/FunctionalJavascript/MediaTypeCreationTest.php b/core/modules/media/tests/src/FunctionalJavascript/MediaTypeCreationTest.php
index 42e3511f315b..a36d263a78b0 100644
--- a/core/modules/media/tests/src/FunctionalJavascript/MediaTypeCreationTest.php
+++ b/core/modules/media/tests/src/FunctionalJavascript/MediaTypeCreationTest.php
@@ -11,6 +11,11 @@
  */
 class MediaTypeCreationTest extends MediaJavascriptTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the source field behavior on the add media type form.
    */
diff --git a/core/modules/media/tests/src/FunctionalJavascript/MediaUiJavascriptTest.php b/core/modules/media/tests/src/FunctionalJavascript/MediaUiJavascriptTest.php
index a00a3c20100c..0bf76924205c 100644
--- a/core/modules/media/tests/src/FunctionalJavascript/MediaUiJavascriptTest.php
+++ b/core/modules/media/tests/src/FunctionalJavascript/MediaUiJavascriptTest.php
@@ -24,6 +24,11 @@ class MediaUiJavascriptTest extends MediaJavascriptTestBase {
     'media_test_source',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The test media type.
    *
diff --git a/core/modules/media/tests/src/FunctionalJavascript/MediaViewsWizardTest.php b/core/modules/media/tests/src/FunctionalJavascript/MediaViewsWizardTest.php
index b602137e7d94..aafa2884e4bb 100644
--- a/core/modules/media/tests/src/FunctionalJavascript/MediaViewsWizardTest.php
+++ b/core/modules/media/tests/src/FunctionalJavascript/MediaViewsWizardTest.php
@@ -14,6 +14,11 @@
  */
 class MediaViewsWizardTest extends MediaJavascriptTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests adding a view of media.
    */
diff --git a/core/modules/media_library/tests/src/Functional/MediaLibraryDisplayModeTest.php b/core/modules/media_library/tests/src/Functional/MediaLibraryDisplayModeTest.php
index 705a1d0aef97..7ebc2bb1b1a7 100644
--- a/core/modules/media_library/tests/src/Functional/MediaLibraryDisplayModeTest.php
+++ b/core/modules/media_library/tests/src/Functional/MediaLibraryDisplayModeTest.php
@@ -29,6 +29,11 @@ class MediaLibraryDisplayModeTest extends BrowserTestBase {
     'system',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/media_library/tests/src/Functional/SettingsFormTest.php b/core/modules/media_library/tests/src/Functional/SettingsFormTest.php
index 35166eade66f..28cc3e0c153c 100644
--- a/core/modules/media_library/tests/src/Functional/SettingsFormTest.php
+++ b/core/modules/media_library/tests/src/Functional/SettingsFormTest.php
@@ -20,6 +20,11 @@ class SettingsFormTest extends BrowserTestBase {
    */
   protected static $modules = ['media_library'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the Media Library settings form.
    */
diff --git a/core/modules/media_library/tests/src/FunctionalJavascript/CKEditorIntegrationTest.php b/core/modules/media_library/tests/src/FunctionalJavascript/CKEditorIntegrationTest.php
index 7c43a4eb89c1..57a556fde645 100644
--- a/core/modules/media_library/tests/src/FunctionalJavascript/CKEditorIntegrationTest.php
+++ b/core/modules/media_library/tests/src/FunctionalJavascript/CKEditorIntegrationTest.php
@@ -24,6 +24,11 @@ class CKEditorIntegrationTest extends WebDriverTestBase {
   use MediaTypeCreationTrait;
   use TestFileCreationTrait;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * The user to use during testing.
    *
diff --git a/core/modules/media_library/tests/src/FunctionalJavascript/ContentModerationTest.php b/core/modules/media_library/tests/src/FunctionalJavascript/ContentModerationTest.php
index dbedfcd620e2..f785235184dc 100644
--- a/core/modules/media_library/tests/src/FunctionalJavascript/ContentModerationTest.php
+++ b/core/modules/media_library/tests/src/FunctionalJavascript/ContentModerationTest.php
@@ -35,6 +35,11 @@ class ContentModerationTest extends WebDriverTestBase {
     'views',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * User with the 'administer media' permission.
    *
diff --git a/core/modules/media_library/tests/src/FunctionalJavascript/EmbeddedFormWidgetTest.php b/core/modules/media_library/tests/src/FunctionalJavascript/EmbeddedFormWidgetTest.php
index 9ac5d0e3c80b..3eacc698ff23 100644
--- a/core/modules/media_library/tests/src/FunctionalJavascript/EmbeddedFormWidgetTest.php
+++ b/core/modules/media_library/tests/src/FunctionalJavascript/EmbeddedFormWidgetTest.php
@@ -25,6 +25,11 @@ class EmbeddedFormWidgetTest extends WebDriverTestBase {
     'media_library_test_widget',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/media_library/tests/src/FunctionalJavascript/MediaLibraryTest.php b/core/modules/media_library/tests/src/FunctionalJavascript/MediaLibraryTest.php
index 5604fa22d20c..87b593f99c3e 100644
--- a/core/modules/media_library/tests/src/FunctionalJavascript/MediaLibraryTest.php
+++ b/core/modules/media_library/tests/src/FunctionalJavascript/MediaLibraryTest.php
@@ -36,6 +36,11 @@ class MediaLibraryTest extends WebDriverTestBase {
     'media_test_oembed',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/media_library/tests/src/FunctionalJavascript/TranslationsTest.php b/core/modules/media_library/tests/src/FunctionalJavascript/TranslationsTest.php
index ff38ef2a3550..0a659b5d8d31 100644
--- a/core/modules/media_library/tests/src/FunctionalJavascript/TranslationsTest.php
+++ b/core/modules/media_library/tests/src/FunctionalJavascript/TranslationsTest.php
@@ -34,6 +34,11 @@ class TranslationsTest extends WebDriverTestBase {
     'views',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/menu_link_content/tests/src/Functional/Hal/MenuLinkContentHalJsonAnonTest.php b/core/modules/menu_link_content/tests/src/Functional/Hal/MenuLinkContentHalJsonAnonTest.php
index d374d2b5a1f9..1438c0cba214 100644
--- a/core/modules/menu_link_content/tests/src/Functional/Hal/MenuLinkContentHalJsonAnonTest.php
+++ b/core/modules/menu_link_content/tests/src/Functional/Hal/MenuLinkContentHalJsonAnonTest.php
@@ -20,6 +20,11 @@ class MenuLinkContentHalJsonAnonTest extends MenuLinkContentResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/menu_link_content/tests/src/Functional/Hal/MenuLinkContentHalJsonBasicAuthTest.php b/core/modules/menu_link_content/tests/src/Functional/Hal/MenuLinkContentHalJsonBasicAuthTest.php
index 40e93a0c7b56..d94f3e98a53f 100644
--- a/core/modules/menu_link_content/tests/src/Functional/Hal/MenuLinkContentHalJsonBasicAuthTest.php
+++ b/core/modules/menu_link_content/tests/src/Functional/Hal/MenuLinkContentHalJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class MenuLinkContentHalJsonBasicAuthTest extends MenuLinkContentHalJsonAnonTest
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/menu_link_content/tests/src/Functional/Hal/MenuLinkContentHalJsonCookieTest.php b/core/modules/menu_link_content/tests/src/Functional/Hal/MenuLinkContentHalJsonCookieTest.php
index 32cba4ac8cd5..aeb7d858e8a3 100644
--- a/core/modules/menu_link_content/tests/src/Functional/Hal/MenuLinkContentHalJsonCookieTest.php
+++ b/core/modules/menu_link_content/tests/src/Functional/Hal/MenuLinkContentHalJsonCookieTest.php
@@ -16,4 +16,9 @@ class MenuLinkContentHalJsonCookieTest extends MenuLinkContentHalJsonAnonTest {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/menu_link_content/tests/src/Functional/MenuLinkContentDeleteFormTest.php b/core/modules/menu_link_content/tests/src/Functional/MenuLinkContentDeleteFormTest.php
index ff829659e3f3..942703ae533d 100644
--- a/core/modules/menu_link_content/tests/src/Functional/MenuLinkContentDeleteFormTest.php
+++ b/core/modules/menu_link_content/tests/src/Functional/MenuLinkContentDeleteFormTest.php
@@ -20,6 +20,11 @@ class MenuLinkContentDeleteFormTest extends BrowserTestBase {
    */
   public static $modules = ['menu_link_content'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/menu_link_content/tests/src/Functional/MenuLinkContentFormTest.php b/core/modules/menu_link_content/tests/src/Functional/MenuLinkContentFormTest.php
index b857667793c8..f205ed794f76 100644
--- a/core/modules/menu_link_content/tests/src/Functional/MenuLinkContentFormTest.php
+++ b/core/modules/menu_link_content/tests/src/Functional/MenuLinkContentFormTest.php
@@ -21,6 +21,11 @@ class MenuLinkContentFormTest extends BrowserTestBase {
     'menu_link_content',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * User with 'administer menu' and 'link to any page' permission.
    *
diff --git a/core/modules/menu_link_content/tests/src/Functional/MenuLinkContentTranslationUITest.php b/core/modules/menu_link_content/tests/src/Functional/MenuLinkContentTranslationUITest.php
index 06d9deb050fd..badeb9cc002f 100644
--- a/core/modules/menu_link_content/tests/src/Functional/MenuLinkContentTranslationUITest.php
+++ b/core/modules/menu_link_content/tests/src/Functional/MenuLinkContentTranslationUITest.php
@@ -29,6 +29,11 @@ class MenuLinkContentTranslationUITest extends ContentTranslationUITestBase {
     'menu_ui',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/menu_link_content/tests/src/Functional/Rest/MenuLinkContentJsonAnonTest.php b/core/modules/menu_link_content/tests/src/Functional/Rest/MenuLinkContentJsonAnonTest.php
index fefd6b1d513c..27ee2909cf71 100644
--- a/core/modules/menu_link_content/tests/src/Functional/Rest/MenuLinkContentJsonAnonTest.php
+++ b/core/modules/menu_link_content/tests/src/Functional/Rest/MenuLinkContentJsonAnonTest.php
@@ -21,4 +21,9 @@ class MenuLinkContentJsonAnonTest extends MenuLinkContentResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/menu_link_content/tests/src/Functional/Rest/MenuLinkContentJsonBasicAuthTest.php b/core/modules/menu_link_content/tests/src/Functional/Rest/MenuLinkContentJsonBasicAuthTest.php
index 269e94991e14..620da15da241 100644
--- a/core/modules/menu_link_content/tests/src/Functional/Rest/MenuLinkContentJsonBasicAuthTest.php
+++ b/core/modules/menu_link_content/tests/src/Functional/Rest/MenuLinkContentJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class MenuLinkContentJsonBasicAuthTest extends MenuLinkContentResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/menu_link_content/tests/src/Functional/Rest/MenuLinkContentJsonCookieTest.php b/core/modules/menu_link_content/tests/src/Functional/Rest/MenuLinkContentJsonCookieTest.php
index 05679525e781..85deeeb6aeec 100644
--- a/core/modules/menu_link_content/tests/src/Functional/Rest/MenuLinkContentJsonCookieTest.php
+++ b/core/modules/menu_link_content/tests/src/Functional/Rest/MenuLinkContentJsonCookieTest.php
@@ -26,4 +26,9 @@ class MenuLinkContentJsonCookieTest extends MenuLinkContentResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/menu_link_content/tests/src/Functional/Rest/MenuLinkContentXmlAnonTest.php b/core/modules/menu_link_content/tests/src/Functional/Rest/MenuLinkContentXmlAnonTest.php
index 7c39dae81dbd..a1c1ed25a1e8 100644
--- a/core/modules/menu_link_content/tests/src/Functional/Rest/MenuLinkContentXmlAnonTest.php
+++ b/core/modules/menu_link_content/tests/src/Functional/Rest/MenuLinkContentXmlAnonTest.php
@@ -23,4 +23,9 @@ class MenuLinkContentXmlAnonTest extends MenuLinkContentResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/menu_link_content/tests/src/Functional/Rest/MenuLinkContentXmlBasicAuthTest.php b/core/modules/menu_link_content/tests/src/Functional/Rest/MenuLinkContentXmlBasicAuthTest.php
index 7bbf966170a1..1e4999e6dea5 100644
--- a/core/modules/menu_link_content/tests/src/Functional/Rest/MenuLinkContentXmlBasicAuthTest.php
+++ b/core/modules/menu_link_content/tests/src/Functional/Rest/MenuLinkContentXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class MenuLinkContentXmlBasicAuthTest extends MenuLinkContentResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/menu_link_content/tests/src/Functional/Rest/MenuLinkContentXmlCookieTest.php b/core/modules/menu_link_content/tests/src/Functional/Rest/MenuLinkContentXmlCookieTest.php
index 8b56dde815c3..310e27c18b03 100644
--- a/core/modules/menu_link_content/tests/src/Functional/Rest/MenuLinkContentXmlCookieTest.php
+++ b/core/modules/menu_link_content/tests/src/Functional/Rest/MenuLinkContentXmlCookieTest.php
@@ -28,4 +28,9 @@ class MenuLinkContentXmlCookieTest extends MenuLinkContentResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/menu_ui/tests/src/Functional/MenuCacheTagsTest.php b/core/modules/menu_ui/tests/src/Functional/MenuCacheTagsTest.php
index c0d36690bcab..4adf2a2e3060 100644
--- a/core/modules/menu_ui/tests/src/Functional/MenuCacheTagsTest.php
+++ b/core/modules/menu_ui/tests/src/Functional/MenuCacheTagsTest.php
@@ -19,6 +19,11 @@ class MenuCacheTagsTest extends PageCacheTagsTestBase {
    */
   public static $modules = ['menu_ui', 'block', 'test_page_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests cache tags presence and invalidation of the Menu entity.
    *
diff --git a/core/modules/menu_ui/tests/src/Functional/MenuLinkReorderTest.php b/core/modules/menu_ui/tests/src/Functional/MenuLinkReorderTest.php
index 4d2bba60d055..88e515857f15 100644
--- a/core/modules/menu_ui/tests/src/Functional/MenuLinkReorderTest.php
+++ b/core/modules/menu_ui/tests/src/Functional/MenuLinkReorderTest.php
@@ -25,6 +25,11 @@ class MenuLinkReorderTest extends BrowserTestBase {
    */
   public static $modules = ['menu_ui', 'test_page_test', 'node', 'block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test creating, editing, deleting menu links via node form widget.
    */
diff --git a/core/modules/menu_ui/tests/src/Functional/MenuUiContentModerationTest.php b/core/modules/menu_ui/tests/src/Functional/MenuUiContentModerationTest.php
index cc86eeff80f9..6aadd290809f 100644
--- a/core/modules/menu_ui/tests/src/Functional/MenuUiContentModerationTest.php
+++ b/core/modules/menu_ui/tests/src/Functional/MenuUiContentModerationTest.php
@@ -21,6 +21,11 @@ class MenuUiContentModerationTest extends BrowserTestBase {
    */
   public static $modules = ['block', 'content_moderation', 'node', 'menu_ui', 'test_page_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/menu_ui/tests/src/Functional/MenuUiLanguageTest.php b/core/modules/menu_ui/tests/src/Functional/MenuUiLanguageTest.php
index 63ebb40215a8..dcdb3277b611 100644
--- a/core/modules/menu_ui/tests/src/Functional/MenuUiLanguageTest.php
+++ b/core/modules/menu_ui/tests/src/Functional/MenuUiLanguageTest.php
@@ -30,6 +30,11 @@ class MenuUiLanguageTest extends BrowserTestBase {
     'menu_ui',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/menu_ui/tests/src/Functional/MenuUiNodeTest.php b/core/modules/menu_ui/tests/src/Functional/MenuUiNodeTest.php
index 57a100a5e18b..df6a47951dfc 100644
--- a/core/modules/menu_ui/tests/src/Functional/MenuUiNodeTest.php
+++ b/core/modules/menu_ui/tests/src/Functional/MenuUiNodeTest.php
@@ -28,6 +28,11 @@ class MenuUiNodeTest extends BrowserTestBase {
    */
   public static $modules = ['menu_ui', 'test_page_test', 'node', 'block', 'locale', 'language', 'content_translation'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/menu_ui/tests/src/Functional/MenuUiTest.php b/core/modules/menu_ui/tests/src/Functional/MenuUiTest.php
index 862f1ccb4831..69114430f293 100644
--- a/core/modules/menu_ui/tests/src/Functional/MenuUiTest.php
+++ b/core/modules/menu_ui/tests/src/Functional/MenuUiTest.php
@@ -39,6 +39,11 @@ class MenuUiTest extends BrowserTestBase {
     'test_page_test',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with administration rights.
    *
diff --git a/core/modules/menu_ui/tests/src/Functional/MenuUninstallTest.php b/core/modules/menu_ui/tests/src/Functional/MenuUninstallTest.php
index b2d64cece5c8..0415ac9a5043 100644
--- a/core/modules/menu_ui/tests/src/Functional/MenuUninstallTest.php
+++ b/core/modules/menu_ui/tests/src/Functional/MenuUninstallTest.php
@@ -19,6 +19,11 @@ class MenuUninstallTest extends BrowserTestBase {
    */
   public static $modules = ['menu_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests Menu uninstall.
    */
diff --git a/core/modules/menu_ui/tests/src/FunctionalJavascript/MenuUiJavascriptTest.php b/core/modules/menu_ui/tests/src/FunctionalJavascript/MenuUiJavascriptTest.php
index 22959326dca9..fea04e60bddf 100644
--- a/core/modules/menu_ui/tests/src/FunctionalJavascript/MenuUiJavascriptTest.php
+++ b/core/modules/menu_ui/tests/src/FunctionalJavascript/MenuUiJavascriptTest.php
@@ -28,6 +28,11 @@ class MenuUiJavascriptTest extends WebDriverTestBase {
     'test_page_test',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the contextual links on a menu block.
    */
diff --git a/core/modules/migrate/tests/src/Functional/process/DownloadFunctionalTest.php b/core/modules/migrate/tests/src/Functional/process/DownloadFunctionalTest.php
index 28824fb094cd..bf6da018c3a5 100644
--- a/core/modules/migrate/tests/src/Functional/process/DownloadFunctionalTest.php
+++ b/core/modules/migrate/tests/src/Functional/process/DownloadFunctionalTest.php
@@ -19,6 +19,11 @@ class DownloadFunctionalTest extends BrowserTestBase {
    */
   public static $modules = ['migrate', 'file'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that an exception is thrown bu migration continues with the next row.
    */
diff --git a/core/modules/migrate_drupal_ui/tests/src/Functional/MigrateAccessTest.php b/core/modules/migrate_drupal_ui/tests/src/Functional/MigrateAccessTest.php
index 3c475e20688f..5a568aec0f56 100644
--- a/core/modules/migrate_drupal_ui/tests/src/Functional/MigrateAccessTest.php
+++ b/core/modules/migrate_drupal_ui/tests/src/Functional/MigrateAccessTest.php
@@ -18,6 +18,11 @@ class MigrateAccessTest extends BrowserTestBase {
    */
   public static $modules = ['migrate_drupal_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that only user 1 can access the migrate UI.
    */
diff --git a/core/modules/migrate_drupal_ui/tests/src/Functional/MigrateUpgradeFormStepsTest.php b/core/modules/migrate_drupal_ui/tests/src/Functional/MigrateUpgradeFormStepsTest.php
index caa60c343839..4ef2738351fb 100644
--- a/core/modules/migrate_drupal_ui/tests/src/Functional/MigrateUpgradeFormStepsTest.php
+++ b/core/modules/migrate_drupal_ui/tests/src/Functional/MigrateUpgradeFormStepsTest.php
@@ -22,6 +22,11 @@ class MigrateUpgradeFormStepsTest extends BrowserTestBase {
    */
   public static $modules = ['migrate_drupal_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/node/tests/src/Functional/Hal/NodeHalJsonAnonTest.php b/core/modules/node/tests/src/Functional/Hal/NodeHalJsonAnonTest.php
index f474c54f7cd1..10f101eb3ffa 100644
--- a/core/modules/node/tests/src/Functional/Hal/NodeHalJsonAnonTest.php
+++ b/core/modules/node/tests/src/Functional/Hal/NodeHalJsonAnonTest.php
@@ -20,6 +20,11 @@ class NodeHalJsonAnonTest extends NodeResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/node/tests/src/Functional/Hal/NodeHalJsonBasicAuthTest.php b/core/modules/node/tests/src/Functional/Hal/NodeHalJsonBasicAuthTest.php
index 0c973a168ef0..fd238757c888 100644
--- a/core/modules/node/tests/src/Functional/Hal/NodeHalJsonBasicAuthTest.php
+++ b/core/modules/node/tests/src/Functional/Hal/NodeHalJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class NodeHalJsonBasicAuthTest extends NodeHalJsonAnonTest {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/node/tests/src/Functional/Hal/NodeHalJsonCookieTest.php b/core/modules/node/tests/src/Functional/Hal/NodeHalJsonCookieTest.php
index e29a58786f75..1c49e78c7d4f 100644
--- a/core/modules/node/tests/src/Functional/Hal/NodeHalJsonCookieTest.php
+++ b/core/modules/node/tests/src/Functional/Hal/NodeHalJsonCookieTest.php
@@ -16,4 +16,9 @@ class NodeHalJsonCookieTest extends NodeHalJsonAnonTest {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/node/tests/src/Functional/Hal/NodeTypeHalJsonAnonTest.php b/core/modules/node/tests/src/Functional/Hal/NodeTypeHalJsonAnonTest.php
index 68f531c89e75..8a7e8d9b6ba5 100644
--- a/core/modules/node/tests/src/Functional/Hal/NodeTypeHalJsonAnonTest.php
+++ b/core/modules/node/tests/src/Functional/Hal/NodeTypeHalJsonAnonTest.php
@@ -17,6 +17,11 @@ class NodeTypeHalJsonAnonTest extends NodeTypeResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/node/tests/src/Functional/Hal/NodeTypeHalJsonBasicAuthTest.php b/core/modules/node/tests/src/Functional/Hal/NodeTypeHalJsonBasicAuthTest.php
index fb7098bdc440..2c8760ba71a8 100644
--- a/core/modules/node/tests/src/Functional/Hal/NodeTypeHalJsonBasicAuthTest.php
+++ b/core/modules/node/tests/src/Functional/Hal/NodeTypeHalJsonBasicAuthTest.php
@@ -17,6 +17,11 @@ class NodeTypeHalJsonBasicAuthTest extends NodeTypeResourceTestBase {
    */
   public static $modules = ['hal', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/node/tests/src/Functional/Hal/NodeTypeHalJsonCookieTest.php b/core/modules/node/tests/src/Functional/Hal/NodeTypeHalJsonCookieTest.php
index 9d7f5a9a32e1..96c7046d0f2e 100644
--- a/core/modules/node/tests/src/Functional/Hal/NodeTypeHalJsonCookieTest.php
+++ b/core/modules/node/tests/src/Functional/Hal/NodeTypeHalJsonCookieTest.php
@@ -17,6 +17,11 @@ class NodeTypeHalJsonCookieTest extends NodeTypeResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/node/tests/src/Functional/MultiStepNodeFormBasicOptionsTest.php b/core/modules/node/tests/src/Functional/MultiStepNodeFormBasicOptionsTest.php
index 7bc1775f4ae3..837d96ce31b4 100644
--- a/core/modules/node/tests/src/Functional/MultiStepNodeFormBasicOptionsTest.php
+++ b/core/modules/node/tests/src/Functional/MultiStepNodeFormBasicOptionsTest.php
@@ -12,6 +12,11 @@
  */
 class MultiStepNodeFormBasicOptionsTest extends NodeTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The field name to create.
    *
diff --git a/core/modules/node/tests/src/Functional/NodeAccessBaseTableTest.php b/core/modules/node/tests/src/Functional/NodeAccessBaseTableTest.php
index f53465051852..4434b0dfe285 100644
--- a/core/modules/node/tests/src/Functional/NodeAccessBaseTableTest.php
+++ b/core/modules/node/tests/src/Functional/NodeAccessBaseTableTest.php
@@ -19,6 +19,11 @@ class NodeAccessBaseTableTest extends NodeTestBase {
    */
   public static $modules = ['node_access_test', 'views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The installation profile to use with this test.
    *
diff --git a/core/modules/node/tests/src/Functional/NodeAccessCacheabilityTest.php b/core/modules/node/tests/src/Functional/NodeAccessCacheabilityTest.php
index 84af1ff18a66..abaee259a1d1 100644
--- a/core/modules/node/tests/src/Functional/NodeAccessCacheabilityTest.php
+++ b/core/modules/node/tests/src/Functional/NodeAccessCacheabilityTest.php
@@ -23,6 +23,11 @@ class NodeAccessCacheabilityTest extends NodeTestBase {
    */
   public static $modules = ['node_access_test', 'node_access_test_auto_bubbling'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/node/tests/src/Functional/NodeAccessFieldTest.php b/core/modules/node/tests/src/Functional/NodeAccessFieldTest.php
index f466886f284c..d92b5ef8a814 100644
--- a/core/modules/node/tests/src/Functional/NodeAccessFieldTest.php
+++ b/core/modules/node/tests/src/Functional/NodeAccessFieldTest.php
@@ -19,6 +19,11 @@ class NodeAccessFieldTest extends NodeTestBase {
    */
   public static $modules = ['node_access_test', 'field_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with permission to bypass access content.
    *
diff --git a/core/modules/node/tests/src/Functional/NodeAccessGrantsCacheContextTest.php b/core/modules/node/tests/src/Functional/NodeAccessGrantsCacheContextTest.php
index e0a466e21dc8..ba9f2bb1547a 100644
--- a/core/modules/node/tests/src/Functional/NodeAccessGrantsCacheContextTest.php
+++ b/core/modules/node/tests/src/Functional/NodeAccessGrantsCacheContextTest.php
@@ -19,6 +19,11 @@ class NodeAccessGrantsCacheContextTest extends NodeTestBase {
    */
   public static $modules = ['node_access_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * User with permission to view content.
    */
diff --git a/core/modules/node/tests/src/Functional/NodeAccessLanguageFallbackTest.php b/core/modules/node/tests/src/Functional/NodeAccessLanguageFallbackTest.php
index 4beacc34235a..b53e36666d2f 100644
--- a/core/modules/node/tests/src/Functional/NodeAccessLanguageFallbackTest.php
+++ b/core/modules/node/tests/src/Functional/NodeAccessLanguageFallbackTest.php
@@ -18,6 +18,11 @@ class NodeAccessLanguageFallbackTest extends NodeTestBase {
    */
   public static $modules = ['language', 'node_access_test', 'content_translation'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/node/tests/src/Functional/NodeAccessMenuLinkTest.php b/core/modules/node/tests/src/Functional/NodeAccessMenuLinkTest.php
index 5d987b36a17d..54c912345dc1 100644
--- a/core/modules/node/tests/src/Functional/NodeAccessMenuLinkTest.php
+++ b/core/modules/node/tests/src/Functional/NodeAccessMenuLinkTest.php
@@ -18,6 +18,11 @@ class NodeAccessMenuLinkTest extends NodeTestBase {
    */
   public static $modules = ['menu_ui', 'block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with permission to manage menu links and create nodes.
    *
diff --git a/core/modules/node/tests/src/Functional/NodeAccessPagerTest.php b/core/modules/node/tests/src/Functional/NodeAccessPagerTest.php
index 6e7e0f216a4d..ba993d46ef20 100644
--- a/core/modules/node/tests/src/Functional/NodeAccessPagerTest.php
+++ b/core/modules/node/tests/src/Functional/NodeAccessPagerTest.php
@@ -23,6 +23,11 @@ class NodeAccessPagerTest extends BrowserTestBase {
    */
   public static $modules = ['node_access_test', 'comment', 'forum'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/node/tests/src/Functional/NodeAccessRebuildNodeGrantsTest.php b/core/modules/node/tests/src/Functional/NodeAccessRebuildNodeGrantsTest.php
index 7ed8413fc798..0e2c6e33dfb8 100644
--- a/core/modules/node/tests/src/Functional/NodeAccessRebuildNodeGrantsTest.php
+++ b/core/modules/node/tests/src/Functional/NodeAccessRebuildNodeGrantsTest.php
@@ -12,6 +12,11 @@
  */
 class NodeAccessRebuildNodeGrantsTest extends NodeTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user to create nodes that only it has access to.
    *
diff --git a/core/modules/node/tests/src/Functional/NodeActionsConfigurationTest.php b/core/modules/node/tests/src/Functional/NodeActionsConfigurationTest.php
index d026902f570f..a93ffb065942 100644
--- a/core/modules/node/tests/src/Functional/NodeActionsConfigurationTest.php
+++ b/core/modules/node/tests/src/Functional/NodeActionsConfigurationTest.php
@@ -19,6 +19,11 @@ class NodeActionsConfigurationTest extends BrowserTestBase {
    */
   public static $modules = ['action', 'node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests configuration of the node_assign_owner_action action.
    */
diff --git a/core/modules/node/tests/src/Functional/NodeAdminTest.php b/core/modules/node/tests/src/Functional/NodeAdminTest.php
index 24c62dda68b8..9cbb42d9d1fc 100644
--- a/core/modules/node/tests/src/Functional/NodeAdminTest.php
+++ b/core/modules/node/tests/src/Functional/NodeAdminTest.php
@@ -11,6 +11,12 @@
  * @group node
  */
 class NodeAdminTest extends NodeTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * A user with permission to bypass access content.
    *
diff --git a/core/modules/node/tests/src/Functional/NodeBlockFunctionalTest.php b/core/modules/node/tests/src/Functional/NodeBlockFunctionalTest.php
index cc8e5703bb76..dc0dfb2ab5f6 100644
--- a/core/modules/node/tests/src/Functional/NodeBlockFunctionalTest.php
+++ b/core/modules/node/tests/src/Functional/NodeBlockFunctionalTest.php
@@ -17,6 +17,11 @@ class NodeBlockFunctionalTest extends NodeTestBase {
 
   use AssertPageCacheContextsAndTagsTrait;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * An administrative user for testing.
    *
diff --git a/core/modules/node/tests/src/Functional/NodeCacheTagsTest.php b/core/modules/node/tests/src/Functional/NodeCacheTagsTest.php
index cae058bd5b4c..14c02669da13 100644
--- a/core/modules/node/tests/src/Functional/NodeCacheTagsTest.php
+++ b/core/modules/node/tests/src/Functional/NodeCacheTagsTest.php
@@ -19,6 +19,11 @@ class NodeCacheTagsTest extends EntityWithUriCacheTagsTestBase {
    */
   public static $modules = ['node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/node/tests/src/Functional/NodeContextualLinksTest.php b/core/modules/node/tests/src/Functional/NodeContextualLinksTest.php
index 0d4aabe6a089..a27bdc0dec63 100644
--- a/core/modules/node/tests/src/Functional/NodeContextualLinksTest.php
+++ b/core/modules/node/tests/src/Functional/NodeContextualLinksTest.php
@@ -18,6 +18,11 @@ class NodeContextualLinksTest extends NodeTestBase {
     'contextual',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests contextual links.
    */
diff --git a/core/modules/node/tests/src/Functional/NodeCreationTest.php b/core/modules/node/tests/src/Functional/NodeCreationTest.php
index b574e58925fb..fd1e2cbd6768 100644
--- a/core/modules/node/tests/src/Functional/NodeCreationTest.php
+++ b/core/modules/node/tests/src/Functional/NodeCreationTest.php
@@ -23,6 +23,11 @@ class NodeCreationTest extends NodeTestBase {
    */
   public static $modules = ['node_test_exception', 'dblog', 'test_page_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/node/tests/src/Functional/NodeDisplayConfigurableTest.php b/core/modules/node/tests/src/Functional/NodeDisplayConfigurableTest.php
index 5bac9abfa953..9193b6efc955 100644
--- a/core/modules/node/tests/src/Functional/NodeDisplayConfigurableTest.php
+++ b/core/modules/node/tests/src/Functional/NodeDisplayConfigurableTest.php
@@ -18,6 +18,11 @@ class NodeDisplayConfigurableTest extends NodeTestBase {
    */
   public static $modules = ['quickedit', 'rdf'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Sets base fields to configurable display and check settings are respected.
    */
diff --git a/core/modules/node/tests/src/Functional/NodeEditFormTest.php b/core/modules/node/tests/src/Functional/NodeEditFormTest.php
index 014f98136361..b4dcc31ba8e7 100644
--- a/core/modules/node/tests/src/Functional/NodeEditFormTest.php
+++ b/core/modules/node/tests/src/Functional/NodeEditFormTest.php
@@ -12,6 +12,11 @@
  */
 class NodeEditFormTest extends NodeTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A normal logged in user.
    *
diff --git a/core/modules/node/tests/src/Functional/NodeEntityViewModeAlterTest.php b/core/modules/node/tests/src/Functional/NodeEntityViewModeAlterTest.php
index be0f1c062305..c51af5d42c2b 100644
--- a/core/modules/node/tests/src/Functional/NodeEntityViewModeAlterTest.php
+++ b/core/modules/node/tests/src/Functional/NodeEntityViewModeAlterTest.php
@@ -19,6 +19,11 @@ class NodeEntityViewModeAlterTest extends NodeTestBase {
    */
   public static $modules = ['node_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Create a "Basic page" node and verify its consistency in the database.
    */
diff --git a/core/modules/node/tests/src/Functional/NodeFieldMultilingualTest.php b/core/modules/node/tests/src/Functional/NodeFieldMultilingualTest.php
index 771426d025a5..7b77d5c6277f 100644
--- a/core/modules/node/tests/src/Functional/NodeFieldMultilingualTest.php
+++ b/core/modules/node/tests/src/Functional/NodeFieldMultilingualTest.php
@@ -22,6 +22,11 @@ class NodeFieldMultilingualTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'language'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/node/tests/src/Functional/NodeFormSaveChangedTimeTest.php b/core/modules/node/tests/src/Functional/NodeFormSaveChangedTimeTest.php
index 607e68cf0d25..6dfd5a73c284 100644
--- a/core/modules/node/tests/src/Functional/NodeFormSaveChangedTimeTest.php
+++ b/core/modules/node/tests/src/Functional/NodeFormSaveChangedTimeTest.php
@@ -20,6 +20,11 @@ class NodeFormSaveChangedTimeTest extends BrowserTestBase {
     'node',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * An user with permissions to create and edit articles.
    *
diff --git a/core/modules/node/tests/src/Functional/NodeHelpTest.php b/core/modules/node/tests/src/Functional/NodeHelpTest.php
index 4dad41618536..971030078220 100644
--- a/core/modules/node/tests/src/Functional/NodeHelpTest.php
+++ b/core/modules/node/tests/src/Functional/NodeHelpTest.php
@@ -18,6 +18,11 @@ class NodeHelpTest extends BrowserTestBase {
    */
   public static $modules = ['block', 'node', 'help'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The name of the test node type to create.
    *
diff --git a/core/modules/node/tests/src/Functional/NodeLinksTest.php b/core/modules/node/tests/src/Functional/NodeLinksTest.php
index 730ba47729a0..31b222d5aabf 100644
--- a/core/modules/node/tests/src/Functional/NodeLinksTest.php
+++ b/core/modules/node/tests/src/Functional/NodeLinksTest.php
@@ -18,6 +18,11 @@ class NodeLinksTest extends NodeTestBase {
    */
   public static $modules = ['views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that the links can be hidden in the view display settings.
    */
diff --git a/core/modules/node/tests/src/Functional/NodeLoadMultipleTest.php b/core/modules/node/tests/src/Functional/NodeLoadMultipleTest.php
index f19d70544884..fa2b3deceb8c 100644
--- a/core/modules/node/tests/src/Functional/NodeLoadMultipleTest.php
+++ b/core/modules/node/tests/src/Functional/NodeLoadMultipleTest.php
@@ -19,6 +19,11 @@ class NodeLoadMultipleTest extends NodeTestBase {
    */
   public static $modules = ['views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     $web_user = $this->drupalCreateUser(['create article content', 'create page content']);
diff --git a/core/modules/node/tests/src/Functional/NodePostSettingsTest.php b/core/modules/node/tests/src/Functional/NodePostSettingsTest.php
index 4716b30067ff..c46558ef7fbb 100644
--- a/core/modules/node/tests/src/Functional/NodePostSettingsTest.php
+++ b/core/modules/node/tests/src/Functional/NodePostSettingsTest.php
@@ -10,6 +10,11 @@
  */
 class NodePostSettingsTest extends NodeTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/node/tests/src/Functional/NodePreviewAnonymousTest.php b/core/modules/node/tests/src/Functional/NodePreviewAnonymousTest.php
index f10d8b7389d6..ff86d237d9a3 100644
--- a/core/modules/node/tests/src/Functional/NodePreviewAnonymousTest.php
+++ b/core/modules/node/tests/src/Functional/NodePreviewAnonymousTest.php
@@ -20,6 +20,11 @@ class NodePreviewAnonymousTest extends BrowserTestBase {
    */
   public static $modules = ['node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/node/tests/src/Functional/NodeQueryAlterTest.php b/core/modules/node/tests/src/Functional/NodeQueryAlterTest.php
index 787def2767d8..d7a0054edc00 100644
--- a/core/modules/node/tests/src/Functional/NodeQueryAlterTest.php
+++ b/core/modules/node/tests/src/Functional/NodeQueryAlterTest.php
@@ -18,6 +18,11 @@ class NodeQueryAlterTest extends NodeTestBase {
    */
   public static $modules = ['node_access_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * User with permission to view content.
    */
diff --git a/core/modules/node/tests/src/Functional/NodeRSSContentTest.php b/core/modules/node/tests/src/Functional/NodeRSSContentTest.php
index 0efa336adecb..6dd1592228a9 100644
--- a/core/modules/node/tests/src/Functional/NodeRSSContentTest.php
+++ b/core/modules/node/tests/src/Functional/NodeRSSContentTest.php
@@ -22,6 +22,11 @@ class NodeRSSContentTest extends NodeTestBase {
    */
   public static $modules = ['node_test', 'views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/node/tests/src/Functional/NodeRevisionPermissionsTest.php b/core/modules/node/tests/src/Functional/NodeRevisionPermissionsTest.php
index 2257b8cfc3f8..3418bcb269ee 100644
--- a/core/modules/node/tests/src/Functional/NodeRevisionPermissionsTest.php
+++ b/core/modules/node/tests/src/Functional/NodeRevisionPermissionsTest.php
@@ -13,6 +13,11 @@ class NodeRevisionPermissionsTest extends NodeTestBase {
 
   use GeneratePermutationsTrait;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The node revisions.
    *
diff --git a/core/modules/node/tests/src/Functional/NodeRevisionsAllTest.php b/core/modules/node/tests/src/Functional/NodeRevisionsAllTest.php
index ba95a5eb3a21..85440bbfcd41 100644
--- a/core/modules/node/tests/src/Functional/NodeRevisionsAllTest.php
+++ b/core/modules/node/tests/src/Functional/NodeRevisionsAllTest.php
@@ -13,6 +13,11 @@
  */
 class NodeRevisionsAllTest extends NodeTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A list of nodes created to be used as starting point of different tests.
    *
diff --git a/core/modules/node/tests/src/Functional/NodeRevisionsTest.php b/core/modules/node/tests/src/Functional/NodeRevisionsTest.php
index 9571f79fa64c..55d6f86721c4 100644
--- a/core/modules/node/tests/src/Functional/NodeRevisionsTest.php
+++ b/core/modules/node/tests/src/Functional/NodeRevisionsTest.php
@@ -19,6 +19,11 @@
  */
 class NodeRevisionsTest extends NodeTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * An array of node revisions.
    *
diff --git a/core/modules/node/tests/src/Functional/NodeRevisionsUiBypassAccessTest.php b/core/modules/node/tests/src/Functional/NodeRevisionsUiBypassAccessTest.php
index 7d58b339277d..d63bb7dca39c 100644
--- a/core/modules/node/tests/src/Functional/NodeRevisionsUiBypassAccessTest.php
+++ b/core/modules/node/tests/src/Functional/NodeRevisionsUiBypassAccessTest.php
@@ -15,6 +15,11 @@
  */
 class NodeRevisionsUiBypassAccessTest extends NodeTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * User with bypass node access permission.
    *
diff --git a/core/modules/node/tests/src/Functional/NodeRevisionsUiTest.php b/core/modules/node/tests/src/Functional/NodeRevisionsUiTest.php
index 8d52571b95b8..861833a45dc3 100644
--- a/core/modules/node/tests/src/Functional/NodeRevisionsUiTest.php
+++ b/core/modules/node/tests/src/Functional/NodeRevisionsUiTest.php
@@ -14,6 +14,11 @@
  */
 class NodeRevisionsUiTest extends NodeTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * @var \Drupal\user\Entity\User
    */
diff --git a/core/modules/node/tests/src/Functional/NodeSaveTest.php b/core/modules/node/tests/src/Functional/NodeSaveTest.php
index 64b38610d60c..d0583b9a4be1 100644
--- a/core/modules/node/tests/src/Functional/NodeSaveTest.php
+++ b/core/modules/node/tests/src/Functional/NodeSaveTest.php
@@ -25,6 +25,11 @@ class NodeSaveTest extends NodeTestBase {
    */
   public static $modules = ['node_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/node/tests/src/Functional/NodeSyndicateBlockTest.php b/core/modules/node/tests/src/Functional/NodeSyndicateBlockTest.php
index c1daef94c91b..f39bb7845579 100644
--- a/core/modules/node/tests/src/Functional/NodeSyndicateBlockTest.php
+++ b/core/modules/node/tests/src/Functional/NodeSyndicateBlockTest.php
@@ -16,6 +16,11 @@ class NodeSyndicateBlockTest extends NodeTestBase {
    */
   public static $modules = ['block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/node/tests/src/Functional/NodeTemplateSuggestionsTest.php b/core/modules/node/tests/src/Functional/NodeTemplateSuggestionsTest.php
index 371cf1c32d6d..1e73f7a9e789 100644
--- a/core/modules/node/tests/src/Functional/NodeTemplateSuggestionsTest.php
+++ b/core/modules/node/tests/src/Functional/NodeTemplateSuggestionsTest.php
@@ -9,6 +9,11 @@
  */
 class NodeTemplateSuggestionsTest extends NodeTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests if template_preprocess_node() generates the correct suggestions.
    */
diff --git a/core/modules/node/tests/src/Functional/NodeTitleTest.php b/core/modules/node/tests/src/Functional/NodeTitleTest.php
index 7985f65ea5e4..0e490320e5fb 100644
--- a/core/modules/node/tests/src/Functional/NodeTitleTest.php
+++ b/core/modules/node/tests/src/Functional/NodeTitleTest.php
@@ -21,6 +21,11 @@ class NodeTitleTest extends NodeTestBase {
    */
   public static $modules = ['comment', 'views', 'block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * A user with permission to bypass access content.
    *
diff --git a/core/modules/node/tests/src/Functional/NodeTitleXSSTest.php b/core/modules/node/tests/src/Functional/NodeTitleXSSTest.php
index 4b750875a2c6..a5302e7042ce 100644
--- a/core/modules/node/tests/src/Functional/NodeTitleXSSTest.php
+++ b/core/modules/node/tests/src/Functional/NodeTitleXSSTest.php
@@ -12,6 +12,11 @@
  */
 class NodeTitleXSSTest extends NodeTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests XSS functionality with a node entity.
    */
diff --git a/core/modules/node/tests/src/Functional/NodeTranslationUITest.php b/core/modules/node/tests/src/Functional/NodeTranslationUITest.php
index 42ca89132223..2201d727d8d3 100644
--- a/core/modules/node/tests/src/Functional/NodeTranslationUITest.php
+++ b/core/modules/node/tests/src/Functional/NodeTranslationUITest.php
@@ -18,6 +18,11 @@
  */
 class NodeTranslationUITest extends ContentTranslationUITestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {inheritdoc}
    */
diff --git a/core/modules/node/tests/src/Functional/NodeTypeInitialLanguageTest.php b/core/modules/node/tests/src/Functional/NodeTypeInitialLanguageTest.php
index 9c442fd5dade..70141772ebde 100644
--- a/core/modules/node/tests/src/Functional/NodeTypeInitialLanguageTest.php
+++ b/core/modules/node/tests/src/Functional/NodeTypeInitialLanguageTest.php
@@ -18,6 +18,11 @@ class NodeTypeInitialLanguageTest extends NodeTestBase {
    */
   public static $modules = ['language', 'field_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/node/tests/src/Functional/NodeTypeTest.php b/core/modules/node/tests/src/Functional/NodeTypeTest.php
index 41f15c0becb3..2977c5970f1b 100644
--- a/core/modules/node/tests/src/Functional/NodeTypeTest.php
+++ b/core/modules/node/tests/src/Functional/NodeTypeTest.php
@@ -25,6 +25,11 @@ class NodeTypeTest extends NodeTestBase {
    */
   public static $modules = ['field_ui', 'block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Ensures that node type functions (node_type_get_*) work correctly.
    *
diff --git a/core/modules/node/tests/src/Functional/NodeTypeTranslationTest.php b/core/modules/node/tests/src/Functional/NodeTypeTranslationTest.php
index 973955c5dd97..925a5f5fcfc7 100644
--- a/core/modules/node/tests/src/Functional/NodeTypeTranslationTest.php
+++ b/core/modules/node/tests/src/Functional/NodeTypeTranslationTest.php
@@ -28,6 +28,11 @@ class NodeTypeTranslationTest extends BrowserTestBase {
     'node',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The default language code to use in this test.
    *
diff --git a/core/modules/node/tests/src/Functional/NodeViewLanguageTest.php b/core/modules/node/tests/src/Functional/NodeViewLanguageTest.php
index e6d466b175e3..5876175a7669 100644
--- a/core/modules/node/tests/src/Functional/NodeViewLanguageTest.php
+++ b/core/modules/node/tests/src/Functional/NodeViewLanguageTest.php
@@ -18,6 +18,11 @@ class NodeViewLanguageTest extends NodeTestBase {
    */
   public static $modules = ['node', 'datetime', 'language'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the language extra field display.
    */
diff --git a/core/modules/node/tests/src/Functional/NodeViewTest.php b/core/modules/node/tests/src/Functional/NodeViewTest.php
index 8704d71570ad..708adb59d64c 100644
--- a/core/modules/node/tests/src/Functional/NodeViewTest.php
+++ b/core/modules/node/tests/src/Functional/NodeViewTest.php
@@ -12,6 +12,11 @@
  */
 class NodeViewTest extends NodeTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Tests the html head links.
    */
diff --git a/core/modules/node/tests/src/Functional/PagePreviewTest.php b/core/modules/node/tests/src/Functional/PagePreviewTest.php
index 26fc64b17e47..428ae121aa0e 100644
--- a/core/modules/node/tests/src/Functional/PagePreviewTest.php
+++ b/core/modules/node/tests/src/Functional/PagePreviewTest.php
@@ -34,6 +34,11 @@ class PagePreviewTest extends NodeTestBase {
    */
   public static $modules = ['node', 'taxonomy', 'comment', 'image', 'file', 'text', 'node_test', 'menu_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * The name of the created field.
    *
diff --git a/core/modules/node/tests/src/Functional/PageViewTest.php b/core/modules/node/tests/src/Functional/PageViewTest.php
index 1f796d83c7cf..30a8dbdfc0b2 100644
--- a/core/modules/node/tests/src/Functional/PageViewTest.php
+++ b/core/modules/node/tests/src/Functional/PageViewTest.php
@@ -11,6 +11,11 @@
  */
 class PageViewTest extends NodeTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests an anonymous and unpermissioned user attempting to edit the node.
    */
diff --git a/core/modules/node/tests/src/Functional/Rest/NodeJsonAnonTest.php b/core/modules/node/tests/src/Functional/Rest/NodeJsonAnonTest.php
index fa44d1386fcd..f434b3b87cf0 100644
--- a/core/modules/node/tests/src/Functional/Rest/NodeJsonAnonTest.php
+++ b/core/modules/node/tests/src/Functional/Rest/NodeJsonAnonTest.php
@@ -21,4 +21,9 @@ class NodeJsonAnonTest extends NodeResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/node/tests/src/Functional/Rest/NodeJsonBasicAuthTest.php b/core/modules/node/tests/src/Functional/Rest/NodeJsonBasicAuthTest.php
index d4ce479c2166..a0bbdfef053e 100644
--- a/core/modules/node/tests/src/Functional/Rest/NodeJsonBasicAuthTest.php
+++ b/core/modules/node/tests/src/Functional/Rest/NodeJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class NodeJsonBasicAuthTest extends NodeResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/node/tests/src/Functional/Rest/NodeJsonCookieTest.php b/core/modules/node/tests/src/Functional/Rest/NodeJsonCookieTest.php
index 0e070bc4d1cd..3cb12de77652 100644
--- a/core/modules/node/tests/src/Functional/Rest/NodeJsonCookieTest.php
+++ b/core/modules/node/tests/src/Functional/Rest/NodeJsonCookieTest.php
@@ -26,4 +26,9 @@ class NodeJsonCookieTest extends NodeResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/node/tests/src/Functional/Rest/NodeTypeJsonAnonTest.php b/core/modules/node/tests/src/Functional/Rest/NodeTypeJsonAnonTest.php
index ab30b17fe5c5..1b8970820ec3 100644
--- a/core/modules/node/tests/src/Functional/Rest/NodeTypeJsonAnonTest.php
+++ b/core/modules/node/tests/src/Functional/Rest/NodeTypeJsonAnonTest.php
@@ -21,4 +21,9 @@ class NodeTypeJsonAnonTest extends NodeTypeResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/node/tests/src/Functional/Rest/NodeTypeJsonBasicAuthTest.php b/core/modules/node/tests/src/Functional/Rest/NodeTypeJsonBasicAuthTest.php
index e1874e4cc638..870f0d0be261 100644
--- a/core/modules/node/tests/src/Functional/Rest/NodeTypeJsonBasicAuthTest.php
+++ b/core/modules/node/tests/src/Functional/Rest/NodeTypeJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class NodeTypeJsonBasicAuthTest extends NodeTypeResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/node/tests/src/Functional/Rest/NodeTypeJsonCookieTest.php b/core/modules/node/tests/src/Functional/Rest/NodeTypeJsonCookieTest.php
index 26608fc7046a..a280615a5850 100644
--- a/core/modules/node/tests/src/Functional/Rest/NodeTypeJsonCookieTest.php
+++ b/core/modules/node/tests/src/Functional/Rest/NodeTypeJsonCookieTest.php
@@ -26,4 +26,9 @@ class NodeTypeJsonCookieTest extends NodeTypeResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/node/tests/src/Functional/Rest/NodeTypeXmlAnonTest.php b/core/modules/node/tests/src/Functional/Rest/NodeTypeXmlAnonTest.php
index c21a9d458bc6..24b2f66e9933 100644
--- a/core/modules/node/tests/src/Functional/Rest/NodeTypeXmlAnonTest.php
+++ b/core/modules/node/tests/src/Functional/Rest/NodeTypeXmlAnonTest.php
@@ -23,4 +23,9 @@ class NodeTypeXmlAnonTest extends NodeTypeResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/node/tests/src/Functional/Rest/NodeTypeXmlBasicAuthTest.php b/core/modules/node/tests/src/Functional/Rest/NodeTypeXmlBasicAuthTest.php
index 29413dc9c2e9..05fb962d7d47 100644
--- a/core/modules/node/tests/src/Functional/Rest/NodeTypeXmlBasicAuthTest.php
+++ b/core/modules/node/tests/src/Functional/Rest/NodeTypeXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class NodeTypeXmlBasicAuthTest extends NodeTypeResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/node/tests/src/Functional/Rest/NodeTypeXmlCookieTest.php b/core/modules/node/tests/src/Functional/Rest/NodeTypeXmlCookieTest.php
index 1326f291ffff..61b21bb98707 100644
--- a/core/modules/node/tests/src/Functional/Rest/NodeTypeXmlCookieTest.php
+++ b/core/modules/node/tests/src/Functional/Rest/NodeTypeXmlCookieTest.php
@@ -28,4 +28,9 @@ class NodeTypeXmlCookieTest extends NodeTypeResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/node/tests/src/Functional/Rest/NodeXmlAnonTest.php b/core/modules/node/tests/src/Functional/Rest/NodeXmlAnonTest.php
index 83e98a171275..5e7716436b9f 100644
--- a/core/modules/node/tests/src/Functional/Rest/NodeXmlAnonTest.php
+++ b/core/modules/node/tests/src/Functional/Rest/NodeXmlAnonTest.php
@@ -23,6 +23,11 @@ class NodeXmlAnonTest extends NodeResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/node/tests/src/Functional/Rest/NodeXmlBasicAuthTest.php b/core/modules/node/tests/src/Functional/Rest/NodeXmlBasicAuthTest.php
index ce809747aa73..9c738ee6be9c 100644
--- a/core/modules/node/tests/src/Functional/Rest/NodeXmlBasicAuthTest.php
+++ b/core/modules/node/tests/src/Functional/Rest/NodeXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class NodeXmlBasicAuthTest extends NodeResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/node/tests/src/Functional/Rest/NodeXmlCookieTest.php b/core/modules/node/tests/src/Functional/Rest/NodeXmlCookieTest.php
index 288d5a143c36..dc479c932d11 100644
--- a/core/modules/node/tests/src/Functional/Rest/NodeXmlCookieTest.php
+++ b/core/modules/node/tests/src/Functional/Rest/NodeXmlCookieTest.php
@@ -28,6 +28,11 @@ class NodeXmlCookieTest extends NodeResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/node/tests/src/Functional/Views/BulkFormAccessTest.php b/core/modules/node/tests/src/Functional/Views/BulkFormAccessTest.php
index a51fe21b7477..1b440cf2f20d 100644
--- a/core/modules/node/tests/src/Functional/Views/BulkFormAccessTest.php
+++ b/core/modules/node/tests/src/Functional/Views/BulkFormAccessTest.php
@@ -24,6 +24,11 @@ class BulkFormAccessTest extends NodeTestBase {
    */
   public static $modules = ['node_test_views', 'node_access_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/node/tests/src/Functional/Views/BulkFormTest.php b/core/modules/node/tests/src/Functional/Views/BulkFormTest.php
index 823093b90649..1ff8c65f8282 100644
--- a/core/modules/node/tests/src/Functional/Views/BulkFormTest.php
+++ b/core/modules/node/tests/src/Functional/Views/BulkFormTest.php
@@ -21,6 +21,11 @@ class BulkFormTest extends NodeTestBase {
    */
   public static $modules = ['node_test_views', 'language'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/node/tests/src/Functional/Views/FilterNodeAccessTest.php b/core/modules/node/tests/src/Functional/Views/FilterNodeAccessTest.php
index f51959062467..e5597d07baa8 100644
--- a/core/modules/node/tests/src/Functional/Views/FilterNodeAccessTest.php
+++ b/core/modules/node/tests/src/Functional/Views/FilterNodeAccessTest.php
@@ -24,6 +24,11 @@ class FilterNodeAccessTest extends NodeTestBase {
    */
   public static $modules = ['node_access_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/node/tests/src/Functional/Views/FrontPageTest.php b/core/modules/node/tests/src/Functional/Views/FrontPageTest.php
index 062bbe010fd1..b7eed1408518 100644
--- a/core/modules/node/tests/src/Functional/Views/FrontPageTest.php
+++ b/core/modules/node/tests/src/Functional/Views/FrontPageTest.php
@@ -21,6 +21,11 @@ class FrontPageTest extends ViewTestBase {
 
   use AssertViewsCacheTagsTrait;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/node/tests/src/Functional/Views/NodeContextualLinksTest.php b/core/modules/node/tests/src/Functional/Views/NodeContextualLinksTest.php
index 73ccfef7582a..9dad4459c64b 100644
--- a/core/modules/node/tests/src/Functional/Views/NodeContextualLinksTest.php
+++ b/core/modules/node/tests/src/Functional/Views/NodeContextualLinksTest.php
@@ -18,6 +18,11 @@ class NodeContextualLinksTest extends NodeTestBase {
    */
   public static $modules = ['contextual'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests if the node page works if Contextual Links is disabled.
    *
diff --git a/core/modules/node/tests/src/Functional/Views/NodeFieldFilterTest.php b/core/modules/node/tests/src/Functional/Views/NodeFieldFilterTest.php
index 154985deaace..43cf14e2257e 100644
--- a/core/modules/node/tests/src/Functional/Views/NodeFieldFilterTest.php
+++ b/core/modules/node/tests/src/Functional/Views/NodeFieldFilterTest.php
@@ -16,6 +16,11 @@ class NodeFieldFilterTest extends NodeTestBase {
    */
   public static $modules = ['language'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/node/tests/src/Functional/Views/NodeFieldTokensTest.php b/core/modules/node/tests/src/Functional/Views/NodeFieldTokensTest.php
index fc547ed370b0..4e32b723ab97 100644
--- a/core/modules/node/tests/src/Functional/Views/NodeFieldTokensTest.php
+++ b/core/modules/node/tests/src/Functional/Views/NodeFieldTokensTest.php
@@ -20,6 +20,11 @@ class NodeFieldTokensTest extends NodeTestBase {
    */
   public static $testViews = ['test_node_tokens'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests token replacement for Views tokens supplied by the Node module.
    */
diff --git a/core/modules/node/tests/src/Functional/Views/NodeIntegrationTest.php b/core/modules/node/tests/src/Functional/Views/NodeIntegrationTest.php
index 0f855d728b82..965e2b3b92b4 100644
--- a/core/modules/node/tests/src/Functional/Views/NodeIntegrationTest.php
+++ b/core/modules/node/tests/src/Functional/Views/NodeIntegrationTest.php
@@ -16,6 +16,11 @@ class NodeIntegrationTest extends NodeTestBase {
    */
   public static $testViews = ['test_node_view'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests basic node view with a node type argument.
    */
diff --git a/core/modules/node/tests/src/Functional/Views/NodeLanguageTest.php b/core/modules/node/tests/src/Functional/Views/NodeLanguageTest.php
index 31e085213cea..012f6dd57cb3 100644
--- a/core/modules/node/tests/src/Functional/Views/NodeLanguageTest.php
+++ b/core/modules/node/tests/src/Functional/Views/NodeLanguageTest.php
@@ -21,6 +21,11 @@ class NodeLanguageTest extends NodeTestBase {
    */
   public static $modules = ['language', 'node_test_views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/node/tests/src/Functional/Views/NodeRevisionWizardTest.php b/core/modules/node/tests/src/Functional/Views/NodeRevisionWizardTest.php
index 2dc97b00c33c..ba2a0c60a8f0 100644
--- a/core/modules/node/tests/src/Functional/Views/NodeRevisionWizardTest.php
+++ b/core/modules/node/tests/src/Functional/Views/NodeRevisionWizardTest.php
@@ -13,6 +13,11 @@
  */
 class NodeRevisionWizardTest extends WizardTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests creating a node revision view.
    */
diff --git a/core/modules/node/tests/src/Functional/Views/PathPluginTest.php b/core/modules/node/tests/src/Functional/Views/PathPluginTest.php
index b1da9fa4b56c..ee9b2acf671e 100644
--- a/core/modules/node/tests/src/Functional/Views/PathPluginTest.php
+++ b/core/modules/node/tests/src/Functional/Views/PathPluginTest.php
@@ -18,6 +18,11 @@ class PathPluginTest extends NodeTestBase {
    */
   public static $modules = ['node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/node/tests/src/Functional/Views/RevisionLinkTest.php b/core/modules/node/tests/src/Functional/Views/RevisionLinkTest.php
index b5a4829b09fd..34f1f7f7fa04 100644
--- a/core/modules/node/tests/src/Functional/Views/RevisionLinkTest.php
+++ b/core/modules/node/tests/src/Functional/Views/RevisionLinkTest.php
@@ -20,6 +20,11 @@ class RevisionLinkTest extends NodeTestBase {
    */
   public static $testViews = ['test_node_revision_links'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests revision links.
    */
diff --git a/core/modules/node/tests/src/Functional/Views/RowPluginTest.php b/core/modules/node/tests/src/Functional/Views/RowPluginTest.php
index fdd4d45ad209..a8627524d116 100644
--- a/core/modules/node/tests/src/Functional/Views/RowPluginTest.php
+++ b/core/modules/node/tests/src/Functional/Views/RowPluginTest.php
@@ -19,6 +19,11 @@ class RowPluginTest extends NodeTestBase {
    */
   public static $modules = ['node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/node/tests/src/Functional/Views/StatusExtraTest.php b/core/modules/node/tests/src/Functional/Views/StatusExtraTest.php
index bce9046d6482..0347038d36fd 100644
--- a/core/modules/node/tests/src/Functional/Views/StatusExtraTest.php
+++ b/core/modules/node/tests/src/Functional/Views/StatusExtraTest.php
@@ -17,6 +17,11 @@ class StatusExtraTest extends NodeTestBase {
    */
   public static $modules = ['node_test_views', 'content_moderation'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/node/tests/src/FunctionalJavascript/ContextualLinksTest.php b/core/modules/node/tests/src/FunctionalJavascript/ContextualLinksTest.php
index 7e9dae071b8e..bf45eb6e1407 100644
--- a/core/modules/node/tests/src/FunctionalJavascript/ContextualLinksTest.php
+++ b/core/modules/node/tests/src/FunctionalJavascript/ContextualLinksTest.php
@@ -28,6 +28,11 @@ class ContextualLinksTest extends WebDriverTestBase {
    */
   protected static $modules = ['node', 'contextual'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/node/tests/src/FunctionalJavascript/NodePreviewLinkTest.php b/core/modules/node/tests/src/FunctionalJavascript/NodePreviewLinkTest.php
index e1c185000f95..ca2f81fe9599 100644
--- a/core/modules/node/tests/src/FunctionalJavascript/NodePreviewLinkTest.php
+++ b/core/modules/node/tests/src/FunctionalJavascript/NodePreviewLinkTest.php
@@ -17,6 +17,11 @@ class NodePreviewLinkTest extends WebDriverTestBase {
    */
   public static $modules = ['node', 'filter'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/node/tests/src/FunctionalJavascript/TestSettingSummariesContentType.php b/core/modules/node/tests/src/FunctionalJavascript/TestSettingSummariesContentType.php
index aef0c1e27d34..9aa6b8dc4047 100644
--- a/core/modules/node/tests/src/FunctionalJavascript/TestSettingSummariesContentType.php
+++ b/core/modules/node/tests/src/FunctionalJavascript/TestSettingSummariesContentType.php
@@ -11,6 +11,11 @@
  */
 class TestSettingSummariesContentType extends WebDriverTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/options/tests/src/Functional/OptionsDynamicValuesApiTest.php b/core/modules/options/tests/src/Functional/OptionsDynamicValuesApiTest.php
index 4f047f97f3b0..a47bc1251fd9 100644
--- a/core/modules/options/tests/src/Functional/OptionsDynamicValuesApiTest.php
+++ b/core/modules/options/tests/src/Functional/OptionsDynamicValuesApiTest.php
@@ -9,6 +9,11 @@
 */
 class OptionsDynamicValuesApiTest extends OptionsDynamicValuesTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests options_allowed_values().
    *
diff --git a/core/modules/options/tests/src/Functional/OptionsDynamicValuesValidationTest.php b/core/modules/options/tests/src/Functional/OptionsDynamicValuesValidationTest.php
index 7ef535c96c16..d44ec3941159 100644
--- a/core/modules/options/tests/src/Functional/OptionsDynamicValuesValidationTest.php
+++ b/core/modules/options/tests/src/Functional/OptionsDynamicValuesValidationTest.php
@@ -9,6 +9,11 @@
  */
 class OptionsDynamicValuesValidationTest extends OptionsDynamicValuesTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test that allowed values function gets the entity.
    */
diff --git a/core/modules/options/tests/src/Functional/OptionsFieldUITest.php b/core/modules/options/tests/src/Functional/OptionsFieldUITest.php
index 7f42998767a0..97e150407f8a 100644
--- a/core/modules/options/tests/src/Functional/OptionsFieldUITest.php
+++ b/core/modules/options/tests/src/Functional/OptionsFieldUITest.php
@@ -21,6 +21,11 @@ class OptionsFieldUITest extends FieldTestBase {
    */
   public static $modules = ['node', 'options', 'field_test', 'taxonomy', 'field_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The name of the created content type.
    *
diff --git a/core/modules/options/tests/src/Functional/OptionsFloatFieldImportTest.php b/core/modules/options/tests/src/Functional/OptionsFloatFieldImportTest.php
index d4d6afff9537..556bc9ba2f32 100644
--- a/core/modules/options/tests/src/Functional/OptionsFloatFieldImportTest.php
+++ b/core/modules/options/tests/src/Functional/OptionsFloatFieldImportTest.php
@@ -20,6 +20,11 @@ class OptionsFloatFieldImportTest extends FieldTestBase {
    */
   public static $modules = ['node', 'options', 'field_ui', 'config', 'options_config_install_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/options/tests/src/Functional/OptionsSelectDynamicValuesTest.php b/core/modules/options/tests/src/Functional/OptionsSelectDynamicValuesTest.php
index 0fb357be04b7..02082cb1d680 100644
--- a/core/modules/options/tests/src/Functional/OptionsSelectDynamicValuesTest.php
+++ b/core/modules/options/tests/src/Functional/OptionsSelectDynamicValuesTest.php
@@ -9,6 +9,11 @@
  */
 class OptionsSelectDynamicValuesTest extends OptionsDynamicValuesTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the 'options_select' widget (single select).
    */
diff --git a/core/modules/options/tests/src/Functional/OptionsWidgetsTest.php b/core/modules/options/tests/src/Functional/OptionsWidgetsTest.php
index b75aacaa7293..ff48c684c2ed 100644
--- a/core/modules/options/tests/src/Functional/OptionsWidgetsTest.php
+++ b/core/modules/options/tests/src/Functional/OptionsWidgetsTest.php
@@ -21,6 +21,11 @@ class OptionsWidgetsTest extends FieldTestBase {
    */
   public static $modules = ['node', 'options', 'entity_test', 'options_test', 'taxonomy', 'field_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A field storage with cardinality 1 to use in this test class.
    *
diff --git a/core/modules/page_cache/tests/src/Functional/PageCacheTest.php b/core/modules/page_cache/tests/src/Functional/PageCacheTest.php
index 88c5311fddf3..553864e7b9c2 100644
--- a/core/modules/page_cache/tests/src/Functional/PageCacheTest.php
+++ b/core/modules/page_cache/tests/src/Functional/PageCacheTest.php
@@ -29,6 +29,11 @@ class PageCacheTest extends BrowserTestBase {
    */
   public static $modules = ['test_page_test', 'system_test', 'entity_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/path/tests/src/Functional/PathAdminTest.php b/core/modules/path/tests/src/Functional/PathAdminTest.php
index 02a9762ffd02..2ac11efa6a3d 100644
--- a/core/modules/path/tests/src/Functional/PathAdminTest.php
+++ b/core/modules/path/tests/src/Functional/PathAdminTest.php
@@ -16,6 +16,11 @@ class PathAdminTest extends PathTestBase {
    */
   public static $modules = ['path'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/path/tests/src/Functional/PathAliasTest.php b/core/modules/path/tests/src/Functional/PathAliasTest.php
index 295430480cd5..4cf25f6d625a 100644
--- a/core/modules/path/tests/src/Functional/PathAliasTest.php
+++ b/core/modules/path/tests/src/Functional/PathAliasTest.php
@@ -21,6 +21,11 @@ class PathAliasTest extends PathTestBase {
    */
   public static $modules = ['path'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/path/tests/src/Functional/PathContentModerationTest.php b/core/modules/path/tests/src/Functional/PathContentModerationTest.php
index b69a5dbe5b5d..cae1928bb825 100644
--- a/core/modules/path/tests/src/Functional/PathContentModerationTest.php
+++ b/core/modules/path/tests/src/Functional/PathContentModerationTest.php
@@ -28,6 +28,11 @@ class PathContentModerationTest extends BrowserTestBase {
     'content_translation',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/path/tests/src/Functional/PathLanguageTest.php b/core/modules/path/tests/src/Functional/PathLanguageTest.php
index ddb512fd799b..18a51749e441 100644
--- a/core/modules/path/tests/src/Functional/PathLanguageTest.php
+++ b/core/modules/path/tests/src/Functional/PathLanguageTest.php
@@ -16,6 +16,11 @@ class PathLanguageTest extends PathTestBase {
    */
   public static $modules = ['path', 'locale', 'locale_test', 'content_translation'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * An user with permissions to administer content types.
    *
diff --git a/core/modules/path/tests/src/Functional/PathLanguageUiTest.php b/core/modules/path/tests/src/Functional/PathLanguageUiTest.php
index b2dc2b0759c9..6ab6e2c22ca6 100644
--- a/core/modules/path/tests/src/Functional/PathLanguageUiTest.php
+++ b/core/modules/path/tests/src/Functional/PathLanguageUiTest.php
@@ -18,6 +18,11 @@ class PathLanguageUiTest extends PathTestBase {
    */
   public static $modules = ['path', 'locale', 'locale_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/path/tests/src/Functional/PathMediaFormTest.php b/core/modules/path/tests/src/Functional/PathMediaFormTest.php
index 7fd3a745bef9..9f34cd85a711 100644
--- a/core/modules/path/tests/src/Functional/PathMediaFormTest.php
+++ b/core/modules/path/tests/src/Functional/PathMediaFormTest.php
@@ -16,6 +16,11 @@ class PathMediaFormTest extends PathTestBase {
    */
   public static $modules = ['media', 'media_test_source'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/path/tests/src/Functional/PathNodeFormTest.php b/core/modules/path/tests/src/Functional/PathNodeFormTest.php
index 9070cc753098..66c6198cc925 100644
--- a/core/modules/path/tests/src/Functional/PathNodeFormTest.php
+++ b/core/modules/path/tests/src/Functional/PathNodeFormTest.php
@@ -16,6 +16,11 @@ class PathNodeFormTest extends PathTestBase {
    */
   public static $modules = ['node', 'path'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/path/tests/src/Functional/PathTaxonomyTermTest.php b/core/modules/path/tests/src/Functional/PathTaxonomyTermTest.php
index ebf3205ae7ae..1db6bb1885d7 100644
--- a/core/modules/path/tests/src/Functional/PathTaxonomyTermTest.php
+++ b/core/modules/path/tests/src/Functional/PathTaxonomyTermTest.php
@@ -19,6 +19,11 @@ class PathTaxonomyTermTest extends PathTestBase {
    */
   public static $modules = ['taxonomy'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/path_alias/tests/src/Functional/Hal/PathAliasHalJsonAnonTest.php b/core/modules/path_alias/tests/src/Functional/Hal/PathAliasHalJsonAnonTest.php
index 22e3f441af25..60917af353cf 100644
--- a/core/modules/path_alias/tests/src/Functional/Hal/PathAliasHalJsonAnonTest.php
+++ b/core/modules/path_alias/tests/src/Functional/Hal/PathAliasHalJsonAnonTest.php
@@ -17,6 +17,11 @@ class PathAliasHalJsonAnonTest extends PathAliasHalJsonTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/path_alias/tests/src/Functional/Hal/PathAliasHalJsonBasicAuthTest.php b/core/modules/path_alias/tests/src/Functional/Hal/PathAliasHalJsonBasicAuthTest.php
index 634c78970bf0..3007a157e0de 100644
--- a/core/modules/path_alias/tests/src/Functional/Hal/PathAliasHalJsonBasicAuthTest.php
+++ b/core/modules/path_alias/tests/src/Functional/Hal/PathAliasHalJsonBasicAuthTest.php
@@ -17,6 +17,11 @@ class PathAliasHalJsonBasicAuthTest extends PathAliasHalJsonTestBase {
    */
   public static $modules = ['hal', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/path_alias/tests/src/Functional/Hal/PathAliasHalJsonCookieTest.php b/core/modules/path_alias/tests/src/Functional/Hal/PathAliasHalJsonCookieTest.php
index 746daaeb4b40..62f39885a364 100644
--- a/core/modules/path_alias/tests/src/Functional/Hal/PathAliasHalJsonCookieTest.php
+++ b/core/modules/path_alias/tests/src/Functional/Hal/PathAliasHalJsonCookieTest.php
@@ -17,6 +17,11 @@ class PathAliasHalJsonCookieTest extends PathAliasHalJsonTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/path_alias/tests/src/Functional/Rest/PathAliasJsonAnonTest.php b/core/modules/path_alias/tests/src/Functional/Rest/PathAliasJsonAnonTest.php
index 8a5c3a79f91a..1e1b4aa21401 100644
--- a/core/modules/path_alias/tests/src/Functional/Rest/PathAliasJsonAnonTest.php
+++ b/core/modules/path_alias/tests/src/Functional/Rest/PathAliasJsonAnonTest.php
@@ -23,4 +23,9 @@ class PathAliasJsonAnonTest extends PathAliasResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/path_alias/tests/src/Functional/Rest/PathAliasJsonBasicAuthTest.php b/core/modules/path_alias/tests/src/Functional/Rest/PathAliasJsonBasicAuthTest.php
index b00359e0cd8f..17cd95e8961f 100644
--- a/core/modules/path_alias/tests/src/Functional/Rest/PathAliasJsonBasicAuthTest.php
+++ b/core/modules/path_alias/tests/src/Functional/Rest/PathAliasJsonBasicAuthTest.php
@@ -18,6 +18,11 @@ class PathAliasJsonBasicAuthTest extends PathAliasResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/path_alias/tests/src/Functional/Rest/PathAliasJsonCookieTest.php b/core/modules/path_alias/tests/src/Functional/Rest/PathAliasJsonCookieTest.php
index a93723d72f30..f620781ed0ad 100644
--- a/core/modules/path_alias/tests/src/Functional/Rest/PathAliasJsonCookieTest.php
+++ b/core/modules/path_alias/tests/src/Functional/Rest/PathAliasJsonCookieTest.php
@@ -28,4 +28,9 @@ class PathAliasJsonCookieTest extends PathAliasResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/path_alias/tests/src/Functional/Rest/PathAliasXmlAnonTest.php b/core/modules/path_alias/tests/src/Functional/Rest/PathAliasXmlAnonTest.php
index 0ab6712f1d65..a987e0dba61d 100644
--- a/core/modules/path_alias/tests/src/Functional/Rest/PathAliasXmlAnonTest.php
+++ b/core/modules/path_alias/tests/src/Functional/Rest/PathAliasXmlAnonTest.php
@@ -25,4 +25,9 @@ class PathAliasXmlAnonTest extends PathAliasResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/path_alias/tests/src/Functional/Rest/PathAliasXmlBasicAuthTest.php b/core/modules/path_alias/tests/src/Functional/Rest/PathAliasXmlBasicAuthTest.php
index 677b5f4d2541..eda55d9f0329 100644
--- a/core/modules/path_alias/tests/src/Functional/Rest/PathAliasXmlBasicAuthTest.php
+++ b/core/modules/path_alias/tests/src/Functional/Rest/PathAliasXmlBasicAuthTest.php
@@ -20,6 +20,11 @@ class PathAliasXmlBasicAuthTest extends PathAliasResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/path_alias/tests/src/Functional/Rest/PathAliasXmlCookieTest.php b/core/modules/path_alias/tests/src/Functional/Rest/PathAliasXmlCookieTest.php
index c5fea144785e..e3695cef3221 100644
--- a/core/modules/path_alias/tests/src/Functional/Rest/PathAliasXmlCookieTest.php
+++ b/core/modules/path_alias/tests/src/Functional/Rest/PathAliasXmlCookieTest.php
@@ -30,4 +30,9 @@ class PathAliasXmlCookieTest extends PathAliasResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/path_alias/tests/src/Functional/UrlAlterFunctionalTest.php b/core/modules/path_alias/tests/src/Functional/UrlAlterFunctionalTest.php
index 58d7079987ae..800c8e86c980 100644
--- a/core/modules/path_alias/tests/src/Functional/UrlAlterFunctionalTest.php
+++ b/core/modules/path_alias/tests/src/Functional/UrlAlterFunctionalTest.php
@@ -25,6 +25,11 @@ class UrlAlterFunctionalTest extends BrowserTestBase {
    */
   public static $modules = ['path', 'forum', 'url_alter_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test that URL altering works and that it occurs in the correct order.
    */
diff --git a/core/modules/quickedit/tests/src/Functional/QuickEditCustomPipelineTest.php b/core/modules/quickedit/tests/src/Functional/QuickEditCustomPipelineTest.php
index 8921a9cf6590..bde1252427fe 100644
--- a/core/modules/quickedit/tests/src/Functional/QuickEditCustomPipelineTest.php
+++ b/core/modules/quickedit/tests/src/Functional/QuickEditCustomPipelineTest.php
@@ -22,6 +22,11 @@ class QuickEditCustomPipelineTest extends BrowserTestBase {
     'node',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that Quick Edit works with custom render pipelines.
    */
diff --git a/core/modules/quickedit/tests/src/Functional/QuickEditEndPointAccessTest.php b/core/modules/quickedit/tests/src/Functional/QuickEditEndPointAccessTest.php
index 8d30a9c94dd0..461b0a7a1af1 100644
--- a/core/modules/quickedit/tests/src/Functional/QuickEditEndPointAccessTest.php
+++ b/core/modules/quickedit/tests/src/Functional/QuickEditEndPointAccessTest.php
@@ -22,6 +22,11 @@ class QuickEditEndPointAccessTest extends BrowserTestBase {
     'node',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/quickedit/tests/src/Functional/QuickEditMinimalTest.php b/core/modules/quickedit/tests/src/Functional/QuickEditMinimalTest.php
index b61dc5ab78ca..2242e97a2611 100644
--- a/core/modules/quickedit/tests/src/Functional/QuickEditMinimalTest.php
+++ b/core/modules/quickedit/tests/src/Functional/QuickEditMinimalTest.php
@@ -24,6 +24,11 @@ class QuickEditMinimalTest extends BrowserTestBase {
     'quickedit_test',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that Quick Edit works with no admin theme.
    *
diff --git a/core/modules/quickedit/tests/src/FunctionalJavascript/FieldTest.php b/core/modules/quickedit/tests/src/FunctionalJavascript/FieldTest.php
index 56d303d659de..0b6505bd40db 100644
--- a/core/modules/quickedit/tests/src/FunctionalJavascript/FieldTest.php
+++ b/core/modules/quickedit/tests/src/FunctionalJavascript/FieldTest.php
@@ -28,6 +28,11 @@ class FieldTest extends WebDriverTestBase {
     'quickedit',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/quickedit/tests/src/FunctionalJavascript/QuickEditAutocompleteTermTest.php b/core/modules/quickedit/tests/src/FunctionalJavascript/QuickEditAutocompleteTermTest.php
index d58f0e7bb5d9..f08ea2d46b1f 100644
--- a/core/modules/quickedit/tests/src/FunctionalJavascript/QuickEditAutocompleteTermTest.php
+++ b/core/modules/quickedit/tests/src/FunctionalJavascript/QuickEditAutocompleteTermTest.php
@@ -31,6 +31,11 @@ class QuickEditAutocompleteTermTest extends WebDriverTestBase {
     'ckeditor',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Stores the node used for the tests.
    *
diff --git a/core/modules/quickedit/tests/src/FunctionalJavascript/QuickEditFileTest.php b/core/modules/quickedit/tests/src/FunctionalJavascript/QuickEditFileTest.php
index a1de95c01bf7..f21ba6d7ab54 100644
--- a/core/modules/quickedit/tests/src/FunctionalJavascript/QuickEditFileTest.php
+++ b/core/modules/quickedit/tests/src/FunctionalJavascript/QuickEditFileTest.php
@@ -23,6 +23,11 @@ class QuickEditFileTest extends QuickEditJavascriptTestBase {
     'file',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/quickedit/tests/src/FunctionalJavascript/QuickEditIntegrationTest.php b/core/modules/quickedit/tests/src/FunctionalJavascript/QuickEditIntegrationTest.php
index 52d645f0f8c1..24f36d440eca 100644
--- a/core/modules/quickedit/tests/src/FunctionalJavascript/QuickEditIntegrationTest.php
+++ b/core/modules/quickedit/tests/src/FunctionalJavascript/QuickEditIntegrationTest.php
@@ -31,6 +31,11 @@ class QuickEditIntegrationTest extends QuickEditJavascriptTestBase {
     'hold_test',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * A user with permissions to edit Articles and use Quick Edit.
    *
diff --git a/core/modules/quickedit/tests/src/FunctionalJavascript/QuickEditLoadingTest.php b/core/modules/quickedit/tests/src/FunctionalJavascript/QuickEditLoadingTest.php
index 2424374570bd..4f52c00efa41 100644
--- a/core/modules/quickedit/tests/src/FunctionalJavascript/QuickEditLoadingTest.php
+++ b/core/modules/quickedit/tests/src/FunctionalJavascript/QuickEditLoadingTest.php
@@ -41,6 +41,11 @@ class QuickEditLoadingTest extends WebDriverTestBase {
     'image',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * An user with permissions to create and edit articles.
    *
diff --git a/core/modules/rdf/tests/src/Functional/CommentAttributesTest.php b/core/modules/rdf/tests/src/Functional/CommentAttributesTest.php
index 6daec72fdc9a..2be1e85cc226 100644
--- a/core/modules/rdf/tests/src/Functional/CommentAttributesTest.php
+++ b/core/modules/rdf/tests/src/Functional/CommentAttributesTest.php
@@ -23,6 +23,11 @@ class CommentAttributesTest extends CommentTestBase {
    */
   public static $modules = ['views', 'node', 'comment', 'rdf'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * URI of the front page of the Drupal site.
    *
diff --git a/core/modules/rdf/tests/src/Functional/EntityReferenceFieldAttributesTest.php b/core/modules/rdf/tests/src/Functional/EntityReferenceFieldAttributesTest.php
index 23468c4fcc63..8c577c1e12bf 100644
--- a/core/modules/rdf/tests/src/Functional/EntityReferenceFieldAttributesTest.php
+++ b/core/modules/rdf/tests/src/Functional/EntityReferenceFieldAttributesTest.php
@@ -20,6 +20,11 @@ class EntityReferenceFieldAttributesTest extends TaxonomyTestBase {
    */
   public static $modules = ['rdf', 'field_test', 'file', 'image'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The name of the taxonomy term reference field used in the test.
    *
diff --git a/core/modules/rdf/tests/src/Functional/FileFieldAttributesTest.php b/core/modules/rdf/tests/src/Functional/FileFieldAttributesTest.php
index f756c9e28db0..fb8eb96c7e09 100644
--- a/core/modules/rdf/tests/src/Functional/FileFieldAttributesTest.php
+++ b/core/modules/rdf/tests/src/Functional/FileFieldAttributesTest.php
@@ -20,6 +20,11 @@ class FileFieldAttributesTest extends FileFieldTestBase {
    */
   public static $modules = ['rdf', 'file'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The name of the file field used in the test.
    *
diff --git a/core/modules/rdf/tests/src/Functional/GetRdfNamespacesTest.php b/core/modules/rdf/tests/src/Functional/GetRdfNamespacesTest.php
index 0b162a4a9055..aade6bc622a6 100644
--- a/core/modules/rdf/tests/src/Functional/GetRdfNamespacesTest.php
+++ b/core/modules/rdf/tests/src/Functional/GetRdfNamespacesTest.php
@@ -18,6 +18,11 @@ class GetRdfNamespacesTest extends BrowserTestBase {
    */
   public static $modules = ['rdf', 'rdf_test_namespaces'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests getting RDF namespaces.
    */
diff --git a/core/modules/rdf/tests/src/Functional/Hal/RdfMappingHalJsonAnonTest.php b/core/modules/rdf/tests/src/Functional/Hal/RdfMappingHalJsonAnonTest.php
index 2d241e99677a..17917981a270 100644
--- a/core/modules/rdf/tests/src/Functional/Hal/RdfMappingHalJsonAnonTest.php
+++ b/core/modules/rdf/tests/src/Functional/Hal/RdfMappingHalJsonAnonTest.php
@@ -17,6 +17,11 @@ class RdfMappingHalJsonAnonTest extends RdfMappingResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/rdf/tests/src/Functional/Hal/RdfMappingHalJsonBasicAuthTest.php b/core/modules/rdf/tests/src/Functional/Hal/RdfMappingHalJsonBasicAuthTest.php
index 346ad229e026..3c9969900a86 100644
--- a/core/modules/rdf/tests/src/Functional/Hal/RdfMappingHalJsonBasicAuthTest.php
+++ b/core/modules/rdf/tests/src/Functional/Hal/RdfMappingHalJsonBasicAuthTest.php
@@ -17,6 +17,11 @@ class RdfMappingHalJsonBasicAuthTest extends RdfMappingResourceTestBase {
    */
   public static $modules = ['hal', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/rdf/tests/src/Functional/Hal/RdfMappingHalJsonCookieTest.php b/core/modules/rdf/tests/src/Functional/Hal/RdfMappingHalJsonCookieTest.php
index ff90d902a1df..8c5c47c0fd03 100644
--- a/core/modules/rdf/tests/src/Functional/Hal/RdfMappingHalJsonCookieTest.php
+++ b/core/modules/rdf/tests/src/Functional/Hal/RdfMappingHalJsonCookieTest.php
@@ -17,6 +17,11 @@ class RdfMappingHalJsonCookieTest extends RdfMappingResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/rdf/tests/src/Functional/ImageFieldAttributesTest.php b/core/modules/rdf/tests/src/Functional/ImageFieldAttributesTest.php
index 9c66230e8009..bd7eab7d7e37 100644
--- a/core/modules/rdf/tests/src/Functional/ImageFieldAttributesTest.php
+++ b/core/modules/rdf/tests/src/Functional/ImageFieldAttributesTest.php
@@ -27,6 +27,11 @@ class ImageFieldAttributesTest extends ImageFieldTestBase {
    */
   public static $modules = ['rdf', 'image'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The name of the image field used in the test.
    *
diff --git a/core/modules/rdf/tests/src/Functional/NodeAttributesTest.php b/core/modules/rdf/tests/src/Functional/NodeAttributesTest.php
index 7811b976b090..00a4a405c485 100644
--- a/core/modules/rdf/tests/src/Functional/NodeAttributesTest.php
+++ b/core/modules/rdf/tests/src/Functional/NodeAttributesTest.php
@@ -19,6 +19,11 @@ class NodeAttributesTest extends NodeTestBase {
    */
   public static $modules = ['rdf'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/rdf/tests/src/Functional/Rest/RdfMappingJsonAnonTest.php b/core/modules/rdf/tests/src/Functional/Rest/RdfMappingJsonAnonTest.php
index bb53cc762259..faed795066f1 100644
--- a/core/modules/rdf/tests/src/Functional/Rest/RdfMappingJsonAnonTest.php
+++ b/core/modules/rdf/tests/src/Functional/Rest/RdfMappingJsonAnonTest.php
@@ -21,4 +21,9 @@ class RdfMappingJsonAnonTest extends RdfMappingResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/rdf/tests/src/Functional/Rest/RdfMappingJsonBasicAuthTest.php b/core/modules/rdf/tests/src/Functional/Rest/RdfMappingJsonBasicAuthTest.php
index 9537336780fd..7727fedfaf25 100644
--- a/core/modules/rdf/tests/src/Functional/Rest/RdfMappingJsonBasicAuthTest.php
+++ b/core/modules/rdf/tests/src/Functional/Rest/RdfMappingJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class RdfMappingJsonBasicAuthTest extends RdfMappingResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/rdf/tests/src/Functional/Rest/RdfMappingJsonCookieTest.php b/core/modules/rdf/tests/src/Functional/Rest/RdfMappingJsonCookieTest.php
index 392d45e9b1ae..768aab6b9dfa 100644
--- a/core/modules/rdf/tests/src/Functional/Rest/RdfMappingJsonCookieTest.php
+++ b/core/modules/rdf/tests/src/Functional/Rest/RdfMappingJsonCookieTest.php
@@ -26,4 +26,9 @@ class RdfMappingJsonCookieTest extends RdfMappingResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/rdf/tests/src/Functional/Rest/RdfMappingXmlAnonTest.php b/core/modules/rdf/tests/src/Functional/Rest/RdfMappingXmlAnonTest.php
index ab6922b8e7aa..a1970f6bd5f7 100644
--- a/core/modules/rdf/tests/src/Functional/Rest/RdfMappingXmlAnonTest.php
+++ b/core/modules/rdf/tests/src/Functional/Rest/RdfMappingXmlAnonTest.php
@@ -23,4 +23,9 @@ class RdfMappingXmlAnonTest extends RdfMappingResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/rdf/tests/src/Functional/Rest/RdfMappingXmlBasicAuthTest.php b/core/modules/rdf/tests/src/Functional/Rest/RdfMappingXmlBasicAuthTest.php
index 9cf6b97d5177..d7a8c1918dc1 100644
--- a/core/modules/rdf/tests/src/Functional/Rest/RdfMappingXmlBasicAuthTest.php
+++ b/core/modules/rdf/tests/src/Functional/Rest/RdfMappingXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class RdfMappingXmlBasicAuthTest extends RdfMappingResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/rdf/tests/src/Functional/Rest/RdfMappingXmlCookieTest.php b/core/modules/rdf/tests/src/Functional/Rest/RdfMappingXmlCookieTest.php
index 1519e5ac725b..c84fdc075555 100644
--- a/core/modules/rdf/tests/src/Functional/Rest/RdfMappingXmlCookieTest.php
+++ b/core/modules/rdf/tests/src/Functional/Rest/RdfMappingXmlCookieTest.php
@@ -28,4 +28,9 @@ class RdfMappingXmlCookieTest extends RdfMappingResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/rdf/tests/src/Functional/StandardProfileTest.php b/core/modules/rdf/tests/src/Functional/StandardProfileTest.php
index a137fb8a8acc..93d78a93a4bf 100644
--- a/core/modules/rdf/tests/src/Functional/StandardProfileTest.php
+++ b/core/modules/rdf/tests/src/Functional/StandardProfileTest.php
@@ -18,6 +18,11 @@
  */
 class StandardProfileTest extends BrowserTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * The profile used during tests.
    *
@@ -105,10 +110,6 @@ class StandardProfileTest extends BrowserTestBase {
   protected function setUp() {
     parent::setUp();
 
-    // Use Classy theme for testing markup output.
-    \Drupal::service('theme_installer')->install(['classy']);
-    $this->config('system.theme')->set('default', 'classy')->save();
-
     $this->baseUri = Url::fromRoute('<front>', [], ['absolute' => TRUE])->toString();
 
     // Create two test users.
diff --git a/core/modules/rdf/tests/src/Functional/TaxonomyAttributesTest.php b/core/modules/rdf/tests/src/Functional/TaxonomyAttributesTest.php
index 7b0720dfad72..529c99b35a3c 100644
--- a/core/modules/rdf/tests/src/Functional/TaxonomyAttributesTest.php
+++ b/core/modules/rdf/tests/src/Functional/TaxonomyAttributesTest.php
@@ -19,6 +19,11 @@ class TaxonomyAttributesTest extends TaxonomyTestBase {
    */
   public static $modules = ['rdf', 'views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Vocabulary created for testing purposes.
    *
diff --git a/core/modules/rdf/tests/src/Functional/UserAttributesTest.php b/core/modules/rdf/tests/src/Functional/UserAttributesTest.php
index 0373e1b49b07..4a38c57f9d07 100644
--- a/core/modules/rdf/tests/src/Functional/UserAttributesTest.php
+++ b/core/modules/rdf/tests/src/Functional/UserAttributesTest.php
@@ -19,6 +19,11 @@ class UserAttributesTest extends BrowserTestBase {
    */
   public static $modules = ['rdf', 'node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     rdf_get_mapping('user', 'user')
diff --git a/core/modules/responsive_image/tests/src/Functional/Hal/ResponsiveImageStyleHalJsonAnonTest.php b/core/modules/responsive_image/tests/src/Functional/Hal/ResponsiveImageStyleHalJsonAnonTest.php
index 50dc1970dfa9..cff45272e384 100644
--- a/core/modules/responsive_image/tests/src/Functional/Hal/ResponsiveImageStyleHalJsonAnonTest.php
+++ b/core/modules/responsive_image/tests/src/Functional/Hal/ResponsiveImageStyleHalJsonAnonTest.php
@@ -17,6 +17,11 @@ class ResponsiveImageStyleHalJsonAnonTest extends ResponsiveImageStyleResourceTe
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/responsive_image/tests/src/Functional/Hal/ResponsiveImageStyleHalJsonBasicAuthTest.php b/core/modules/responsive_image/tests/src/Functional/Hal/ResponsiveImageStyleHalJsonBasicAuthTest.php
index 1f45a2d74367..17e896ee20bc 100644
--- a/core/modules/responsive_image/tests/src/Functional/Hal/ResponsiveImageStyleHalJsonBasicAuthTest.php
+++ b/core/modules/responsive_image/tests/src/Functional/Hal/ResponsiveImageStyleHalJsonBasicAuthTest.php
@@ -22,6 +22,11 @@ class ResponsiveImageStyleHalJsonBasicAuthTest extends ResponsiveImageStyleResou
    */
   protected static $format = 'hal_json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/responsive_image/tests/src/Functional/Hal/ResponsiveImageStyleHalJsonCookieTest.php b/core/modules/responsive_image/tests/src/Functional/Hal/ResponsiveImageStyleHalJsonCookieTest.php
index 85d95431f58d..3d32819dbc15 100644
--- a/core/modules/responsive_image/tests/src/Functional/Hal/ResponsiveImageStyleHalJsonCookieTest.php
+++ b/core/modules/responsive_image/tests/src/Functional/Hal/ResponsiveImageStyleHalJsonCookieTest.php
@@ -17,6 +17,11 @@ class ResponsiveImageStyleHalJsonCookieTest extends ResponsiveImageStyleResource
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/responsive_image/tests/src/Functional/ResponsiveImageAdminUITest.php b/core/modules/responsive_image/tests/src/Functional/ResponsiveImageAdminUITest.php
index 8dc5e24d3a41..72de87c886f5 100644
--- a/core/modules/responsive_image/tests/src/Functional/ResponsiveImageAdminUITest.php
+++ b/core/modules/responsive_image/tests/src/Functional/ResponsiveImageAdminUITest.php
@@ -19,6 +19,11 @@ class ResponsiveImageAdminUITest extends BrowserTestBase {
    */
   public static $modules = ['responsive_image', 'responsive_image_test_module'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Drupal\simpletest\WebTestBase\setUp().
    */
diff --git a/core/modules/responsive_image/tests/src/Functional/ResponsiveImageFieldDisplayTest.php b/core/modules/responsive_image/tests/src/Functional/ResponsiveImageFieldDisplayTest.php
index ae9f7be86dd8..9b805d6e625f 100644
--- a/core/modules/responsive_image/tests/src/Functional/ResponsiveImageFieldDisplayTest.php
+++ b/core/modules/responsive_image/tests/src/Functional/ResponsiveImageFieldDisplayTest.php
@@ -21,6 +21,11 @@ class ResponsiveImageFieldDisplayTest extends ImageFieldTestBase {
 
   use TestFileCreationTrait;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected $dumpHeaders = TRUE;
 
   /**
diff --git a/core/modules/responsive_image/tests/src/Functional/Rest/ResponsiveImageStyleJsonAnonTest.php b/core/modules/responsive_image/tests/src/Functional/Rest/ResponsiveImageStyleJsonAnonTest.php
index 42b3098dd5a6..2b35fd2b5704 100644
--- a/core/modules/responsive_image/tests/src/Functional/Rest/ResponsiveImageStyleJsonAnonTest.php
+++ b/core/modules/responsive_image/tests/src/Functional/Rest/ResponsiveImageStyleJsonAnonTest.php
@@ -21,4 +21,9 @@ class ResponsiveImageStyleJsonAnonTest extends ResponsiveImageStyleResourceTestB
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/responsive_image/tests/src/Functional/Rest/ResponsiveImageStyleJsonBasicAuthTest.php b/core/modules/responsive_image/tests/src/Functional/Rest/ResponsiveImageStyleJsonBasicAuthTest.php
index b3c9127da412..76eadc341eec 100644
--- a/core/modules/responsive_image/tests/src/Functional/Rest/ResponsiveImageStyleJsonBasicAuthTest.php
+++ b/core/modules/responsive_image/tests/src/Functional/Rest/ResponsiveImageStyleJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class ResponsiveImageStyleJsonBasicAuthTest extends ResponsiveImageStyleResource
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/responsive_image/tests/src/Functional/Rest/ResponsiveImageStyleJsonCookieTest.php b/core/modules/responsive_image/tests/src/Functional/Rest/ResponsiveImageStyleJsonCookieTest.php
index e89122eab66d..4e78c8aa31f8 100644
--- a/core/modules/responsive_image/tests/src/Functional/Rest/ResponsiveImageStyleJsonCookieTest.php
+++ b/core/modules/responsive_image/tests/src/Functional/Rest/ResponsiveImageStyleJsonCookieTest.php
@@ -26,4 +26,9 @@ class ResponsiveImageStyleJsonCookieTest extends ResponsiveImageStyleResourceTes
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/responsive_image/tests/src/Functional/Rest/ResponsiveImageStyleXmlAnonTest.php b/core/modules/responsive_image/tests/src/Functional/Rest/ResponsiveImageStyleXmlAnonTest.php
index 8493eddabee8..b07b2b06b5d7 100644
--- a/core/modules/responsive_image/tests/src/Functional/Rest/ResponsiveImageStyleXmlAnonTest.php
+++ b/core/modules/responsive_image/tests/src/Functional/Rest/ResponsiveImageStyleXmlAnonTest.php
@@ -23,4 +23,9 @@ class ResponsiveImageStyleXmlAnonTest extends ResponsiveImageStyleResourceTestBa
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/responsive_image/tests/src/Functional/Rest/ResponsiveImageStyleXmlBasicAuthTest.php b/core/modules/responsive_image/tests/src/Functional/Rest/ResponsiveImageStyleXmlBasicAuthTest.php
index e850e99d57ba..75b6ead6be61 100644
--- a/core/modules/responsive_image/tests/src/Functional/Rest/ResponsiveImageStyleXmlBasicAuthTest.php
+++ b/core/modules/responsive_image/tests/src/Functional/Rest/ResponsiveImageStyleXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class ResponsiveImageStyleXmlBasicAuthTest extends ResponsiveImageStyleResourceT
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/responsive_image/tests/src/Functional/Rest/ResponsiveImageStyleXmlCookieTest.php b/core/modules/responsive_image/tests/src/Functional/Rest/ResponsiveImageStyleXmlCookieTest.php
index f63f91cd5425..f71632b757d1 100644
--- a/core/modules/responsive_image/tests/src/Functional/Rest/ResponsiveImageStyleXmlCookieTest.php
+++ b/core/modules/responsive_image/tests/src/Functional/Rest/ResponsiveImageStyleXmlCookieTest.php
@@ -28,4 +28,9 @@ class ResponsiveImageStyleXmlCookieTest extends ResponsiveImageStyleResourceTest
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/responsive_image/tests/src/Functional/ViewsIntegrationTest.php b/core/modules/responsive_image/tests/src/Functional/ViewsIntegrationTest.php
index 33f19a5be564..4a926dffdf6d 100644
--- a/core/modules/responsive_image/tests/src/Functional/ViewsIntegrationTest.php
+++ b/core/modules/responsive_image/tests/src/Functional/ViewsIntegrationTest.php
@@ -34,6 +34,11 @@ class ViewsIntegrationTest extends ViewTestBase {
     'responsive_image_test_module',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The test views to enable.
    */
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceRestTestCoverageTest.php b/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceRestTestCoverageTest.php
index 82d47b95a7f5..8be771f31c26 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceRestTestCoverageTest.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceRestTestCoverageTest.php
@@ -23,6 +23,11 @@ class EntityResourceRestTestCoverageTest extends BrowserTestBase {
    */
   protected $definitions;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/ModeratedNode/ModeratedNodeJsonAnonTest.php b/core/modules/rest/tests/src/Functional/EntityResource/ModeratedNode/ModeratedNodeJsonAnonTest.php
index f28788ac8018..c5b18daa94b1 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/ModeratedNode/ModeratedNodeJsonAnonTest.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/ModeratedNode/ModeratedNodeJsonAnonTest.php
@@ -21,4 +21,9 @@ class ModeratedNodeJsonAnonTest extends ModeratedNodeResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/ModeratedNode/ModeratedNodeJsonBasicAuthTest.php b/core/modules/rest/tests/src/Functional/EntityResource/ModeratedNode/ModeratedNodeJsonBasicAuthTest.php
index b47a86f65ffb..e1051e94144b 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/ModeratedNode/ModeratedNodeJsonBasicAuthTest.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/ModeratedNode/ModeratedNodeJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class ModeratedNodeJsonBasicAuthTest extends ModeratedNodeResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/ModeratedNode/ModeratedNodeJsonCookieTest.php b/core/modules/rest/tests/src/Functional/EntityResource/ModeratedNode/ModeratedNodeJsonCookieTest.php
index 08fc4b5f4fb0..ffcb5e094767 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/ModeratedNode/ModeratedNodeJsonCookieTest.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/ModeratedNode/ModeratedNodeJsonCookieTest.php
@@ -26,4 +26,9 @@ class ModeratedNodeJsonCookieTest extends ModeratedNodeResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/ModeratedNode/ModeratedNodeXmlAnonTest.php b/core/modules/rest/tests/src/Functional/EntityResource/ModeratedNode/ModeratedNodeXmlAnonTest.php
index 4b91d766c6f4..3cc3853df1be 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/ModeratedNode/ModeratedNodeXmlAnonTest.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/ModeratedNode/ModeratedNodeXmlAnonTest.php
@@ -23,6 +23,11 @@ class ModeratedNodeXmlAnonTest extends ModeratedNodeResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/ModeratedNode/ModeratedNodeXmlBasicAuthTest.php b/core/modules/rest/tests/src/Functional/EntityResource/ModeratedNode/ModeratedNodeXmlBasicAuthTest.php
index a321e03cb25f..9977177b7cd4 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/ModeratedNode/ModeratedNodeXmlBasicAuthTest.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/ModeratedNode/ModeratedNodeXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class ModeratedNodeXmlBasicAuthTest extends ModeratedNodeResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/ModeratedNode/ModeratedNodeXmlCookieTest.php b/core/modules/rest/tests/src/Functional/EntityResource/ModeratedNode/ModeratedNodeXmlCookieTest.php
index 2014a56ff43d..8a2193fb90db 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/ModeratedNode/ModeratedNodeXmlCookieTest.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/ModeratedNode/ModeratedNodeXmlCookieTest.php
@@ -28,6 +28,11 @@ class ModeratedNodeXmlCookieTest extends ModeratedNodeResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/rest/tests/src/Functional/Hal/RestResourceConfigHalJsonAnonTest.php b/core/modules/rest/tests/src/Functional/Hal/RestResourceConfigHalJsonAnonTest.php
index 72ccd45e932a..7731048a858c 100644
--- a/core/modules/rest/tests/src/Functional/Hal/RestResourceConfigHalJsonAnonTest.php
+++ b/core/modules/rest/tests/src/Functional/Hal/RestResourceConfigHalJsonAnonTest.php
@@ -17,6 +17,11 @@ class RestResourceConfigHalJsonAnonTest extends RestResourceConfigResourceTestBa
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/rest/tests/src/Functional/Hal/RestResourceConfigHalJsonBasicAuthTest.php b/core/modules/rest/tests/src/Functional/Hal/RestResourceConfigHalJsonBasicAuthTest.php
index e5e9a7efbbff..e220693e9f5c 100644
--- a/core/modules/rest/tests/src/Functional/Hal/RestResourceConfigHalJsonBasicAuthTest.php
+++ b/core/modules/rest/tests/src/Functional/Hal/RestResourceConfigHalJsonBasicAuthTest.php
@@ -17,6 +17,11 @@ class RestResourceConfigHalJsonBasicAuthTest extends RestResourceConfigResourceT
    */
   public static $modules = ['hal', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/rest/tests/src/Functional/Hal/RestResourceConfigHalJsonCookieTest.php b/core/modules/rest/tests/src/Functional/Hal/RestResourceConfigHalJsonCookieTest.php
index 606d3fd64132..d224369f6af8 100644
--- a/core/modules/rest/tests/src/Functional/Hal/RestResourceConfigHalJsonCookieTest.php
+++ b/core/modules/rest/tests/src/Functional/Hal/RestResourceConfigHalJsonCookieTest.php
@@ -17,6 +17,11 @@ class RestResourceConfigHalJsonCookieTest extends RestResourceConfigResourceTest
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/rest/tests/src/Functional/ResourceTest.php b/core/modules/rest/tests/src/Functional/ResourceTest.php
index 5a569106910d..57a6840bff31 100644
--- a/core/modules/rest/tests/src/Functional/ResourceTest.php
+++ b/core/modules/rest/tests/src/Functional/ResourceTest.php
@@ -25,6 +25,11 @@ class ResourceTest extends BrowserTestBase {
    */
   public static $modules = ['hal', 'rest', 'entity_test', 'rest_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The entity.
    *
diff --git a/core/modules/rest/tests/src/Functional/Rest/RestResourceConfigJsonAnonTest.php b/core/modules/rest/tests/src/Functional/Rest/RestResourceConfigJsonAnonTest.php
index ce355909d11e..0caad8c81922 100644
--- a/core/modules/rest/tests/src/Functional/Rest/RestResourceConfigJsonAnonTest.php
+++ b/core/modules/rest/tests/src/Functional/Rest/RestResourceConfigJsonAnonTest.php
@@ -21,4 +21,9 @@ class RestResourceConfigJsonAnonTest extends RestResourceConfigResourceTestBase
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/rest/tests/src/Functional/Rest/RestResourceConfigJsonBasicAuthTest.php b/core/modules/rest/tests/src/Functional/Rest/RestResourceConfigJsonBasicAuthTest.php
index 8ac84636ec31..7a1f9c0a5848 100644
--- a/core/modules/rest/tests/src/Functional/Rest/RestResourceConfigJsonBasicAuthTest.php
+++ b/core/modules/rest/tests/src/Functional/Rest/RestResourceConfigJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class RestResourceConfigJsonBasicAuthTest extends RestResourceConfigResourceTest
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/rest/tests/src/Functional/Rest/RestResourceConfigJsonCookieTest.php b/core/modules/rest/tests/src/Functional/Rest/RestResourceConfigJsonCookieTest.php
index 4971f59a44eb..0fee7a1c4f69 100644
--- a/core/modules/rest/tests/src/Functional/Rest/RestResourceConfigJsonCookieTest.php
+++ b/core/modules/rest/tests/src/Functional/Rest/RestResourceConfigJsonCookieTest.php
@@ -26,4 +26,9 @@ class RestResourceConfigJsonCookieTest extends RestResourceConfigResourceTestBas
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/rest/tests/src/Functional/Rest/RestResourceConfigXmlAnonTest.php b/core/modules/rest/tests/src/Functional/Rest/RestResourceConfigXmlAnonTest.php
index a508b55409d7..5c0c24e47a7d 100644
--- a/core/modules/rest/tests/src/Functional/Rest/RestResourceConfigXmlAnonTest.php
+++ b/core/modules/rest/tests/src/Functional/Rest/RestResourceConfigXmlAnonTest.php
@@ -23,4 +23,9 @@ class RestResourceConfigXmlAnonTest extends RestResourceConfigResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/rest/tests/src/Functional/Rest/RestResourceConfigXmlBasicAuthTest.php b/core/modules/rest/tests/src/Functional/Rest/RestResourceConfigXmlBasicAuthTest.php
index c5034b4ee5cc..df9e46e251ce 100644
--- a/core/modules/rest/tests/src/Functional/Rest/RestResourceConfigXmlBasicAuthTest.php
+++ b/core/modules/rest/tests/src/Functional/Rest/RestResourceConfigXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class RestResourceConfigXmlBasicAuthTest extends RestResourceConfigResourceTestB
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/rest/tests/src/Functional/Rest/RestResourceConfigXmlCookieTest.php b/core/modules/rest/tests/src/Functional/Rest/RestResourceConfigXmlCookieTest.php
index 377a4497e971..796d5424f848 100644
--- a/core/modules/rest/tests/src/Functional/Rest/RestResourceConfigXmlCookieTest.php
+++ b/core/modules/rest/tests/src/Functional/Rest/RestResourceConfigXmlCookieTest.php
@@ -28,4 +28,9 @@ class RestResourceConfigXmlCookieTest extends RestResourceConfigResourceTestBase
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/rest/tests/src/Functional/Views/ExcludedFieldTokenTest.php b/core/modules/rest/tests/src/Functional/Views/ExcludedFieldTokenTest.php
index cf9913d85a43..22d583fde6b9 100644
--- a/core/modules/rest/tests/src/Functional/Views/ExcludedFieldTokenTest.php
+++ b/core/modules/rest/tests/src/Functional/Views/ExcludedFieldTokenTest.php
@@ -28,6 +28,11 @@ class ExcludedFieldTokenTest extends ViewTestBase {
    */
   public static $testViews = ['test_excluded_field_token_display'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The modules that need to be installed for this test.
    *
diff --git a/core/modules/rest/tests/src/Functional/Views/FieldCounterTest.php b/core/modules/rest/tests/src/Functional/Views/FieldCounterTest.php
index 8d3e4f755041..ef8d0a034b2c 100644
--- a/core/modules/rest/tests/src/Functional/Views/FieldCounterTest.php
+++ b/core/modules/rest/tests/src/Functional/Views/FieldCounterTest.php
@@ -28,6 +28,11 @@ class FieldCounterTest extends ViewTestBase {
    */
   public static $testViews = ['test_field_counter_display'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The modules that need to be installed for this test.
    *
diff --git a/core/modules/rest/tests/src/Functional/Views/RestExportAuthTest.php b/core/modules/rest/tests/src/Functional/Views/RestExportAuthTest.php
index 24546089cd54..4b692260114c 100644
--- a/core/modules/rest/tests/src/Functional/Views/RestExportAuthTest.php
+++ b/core/modules/rest/tests/src/Functional/Views/RestExportAuthTest.php
@@ -17,6 +17,11 @@ class RestExportAuthTest extends ViewTestBase {
    */
   public static $modules = ['rest', 'views_ui', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/rest/tests/src/Functional/Views/StyleSerializerTest.php b/core/modules/rest/tests/src/Functional/Views/StyleSerializerTest.php
index e307c77bc48f..c0de5c8578da 100644
--- a/core/modules/rest/tests/src/Functional/Views/StyleSerializerTest.php
+++ b/core/modules/rest/tests/src/Functional/Views/StyleSerializerTest.php
@@ -38,6 +38,11 @@ class StyleSerializerTest extends ViewTestBase {
    */
   public static $modules = ['views_ui', 'entity_test', 'hal', 'rest_test_views', 'node', 'text', 'field', 'language', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/search/tests/src/Functional/Hal/SearchPageHalJsonAnonTest.php b/core/modules/search/tests/src/Functional/Hal/SearchPageHalJsonAnonTest.php
index cd0079803ce7..833c59beed1b 100644
--- a/core/modules/search/tests/src/Functional/Hal/SearchPageHalJsonAnonTest.php
+++ b/core/modules/search/tests/src/Functional/Hal/SearchPageHalJsonAnonTest.php
@@ -17,6 +17,11 @@ class SearchPageHalJsonAnonTest extends SearchPageResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/search/tests/src/Functional/Hal/SearchPageHalJsonBasicAuthTest.php b/core/modules/search/tests/src/Functional/Hal/SearchPageHalJsonBasicAuthTest.php
index d1ff293ba369..d7e8a619bffe 100644
--- a/core/modules/search/tests/src/Functional/Hal/SearchPageHalJsonBasicAuthTest.php
+++ b/core/modules/search/tests/src/Functional/Hal/SearchPageHalJsonBasicAuthTest.php
@@ -17,6 +17,11 @@ class SearchPageHalJsonBasicAuthTest extends SearchPageResourceTestBase {
    */
   public static $modules = ['hal', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/search/tests/src/Functional/Hal/SearchPageHalJsonCookieTest.php b/core/modules/search/tests/src/Functional/Hal/SearchPageHalJsonCookieTest.php
index a09fa5f9b123..47ab4dd46b74 100644
--- a/core/modules/search/tests/src/Functional/Hal/SearchPageHalJsonCookieTest.php
+++ b/core/modules/search/tests/src/Functional/Hal/SearchPageHalJsonCookieTest.php
@@ -17,6 +17,11 @@ class SearchPageHalJsonCookieTest extends SearchPageResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/search/tests/src/Functional/Rest/SearchPageJsonAnonTest.php b/core/modules/search/tests/src/Functional/Rest/SearchPageJsonAnonTest.php
index 9708192642d5..b58490208f0d 100644
--- a/core/modules/search/tests/src/Functional/Rest/SearchPageJsonAnonTest.php
+++ b/core/modules/search/tests/src/Functional/Rest/SearchPageJsonAnonTest.php
@@ -21,4 +21,9 @@ class SearchPageJsonAnonTest extends SearchPageResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/search/tests/src/Functional/Rest/SearchPageJsonBasicAuthTest.php b/core/modules/search/tests/src/Functional/Rest/SearchPageJsonBasicAuthTest.php
index f311ce9b4d50..615393be6fba 100644
--- a/core/modules/search/tests/src/Functional/Rest/SearchPageJsonBasicAuthTest.php
+++ b/core/modules/search/tests/src/Functional/Rest/SearchPageJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class SearchPageJsonBasicAuthTest extends SearchPageResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/search/tests/src/Functional/Rest/SearchPageJsonCookieTest.php b/core/modules/search/tests/src/Functional/Rest/SearchPageJsonCookieTest.php
index 8e7c8899d473..ca6c6a386242 100644
--- a/core/modules/search/tests/src/Functional/Rest/SearchPageJsonCookieTest.php
+++ b/core/modules/search/tests/src/Functional/Rest/SearchPageJsonCookieTest.php
@@ -26,4 +26,9 @@ class SearchPageJsonCookieTest extends SearchPageResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/search/tests/src/Functional/Rest/SearchPageXmlAnonTest.php b/core/modules/search/tests/src/Functional/Rest/SearchPageXmlAnonTest.php
index 5f4698ec1bfb..3ed7990aa546 100644
--- a/core/modules/search/tests/src/Functional/Rest/SearchPageXmlAnonTest.php
+++ b/core/modules/search/tests/src/Functional/Rest/SearchPageXmlAnonTest.php
@@ -23,4 +23,9 @@ class SearchPageXmlAnonTest extends SearchPageResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/search/tests/src/Functional/Rest/SearchPageXmlBasicAuthTest.php b/core/modules/search/tests/src/Functional/Rest/SearchPageXmlBasicAuthTest.php
index 7a2c3c8804c9..5381043bee93 100644
--- a/core/modules/search/tests/src/Functional/Rest/SearchPageXmlBasicAuthTest.php
+++ b/core/modules/search/tests/src/Functional/Rest/SearchPageXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class SearchPageXmlBasicAuthTest extends SearchPageResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/search/tests/src/Functional/Rest/SearchPageXmlCookieTest.php b/core/modules/search/tests/src/Functional/Rest/SearchPageXmlCookieTest.php
index 3ad901d6ef1a..860981f09f66 100644
--- a/core/modules/search/tests/src/Functional/Rest/SearchPageXmlCookieTest.php
+++ b/core/modules/search/tests/src/Functional/Rest/SearchPageXmlCookieTest.php
@@ -28,4 +28,9 @@ class SearchPageXmlCookieTest extends SearchPageResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/search/tests/src/Functional/SearchAdvancedSearchFormTest.php b/core/modules/search/tests/src/Functional/SearchAdvancedSearchFormTest.php
index 7933dfd9b965..099663ed59d0 100644
--- a/core/modules/search/tests/src/Functional/SearchAdvancedSearchFormTest.php
+++ b/core/modules/search/tests/src/Functional/SearchAdvancedSearchFormTest.php
@@ -16,6 +16,11 @@ class SearchAdvancedSearchFormTest extends BrowserTestBase {
    */
   protected static $modules = ['node', 'search', 'dblog'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A node to use for testing.
    *
diff --git a/core/modules/search/tests/src/Functional/SearchBlockTest.php b/core/modules/search/tests/src/Functional/SearchBlockTest.php
index 31e16b13b993..07791269c5a7 100644
--- a/core/modules/search/tests/src/Functional/SearchBlockTest.php
+++ b/core/modules/search/tests/src/Functional/SearchBlockTest.php
@@ -17,6 +17,11 @@ class SearchBlockTest extends BrowserTestBase {
    */
   protected static $modules = ['block', 'node', 'search', 'dblog', 'user'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * The administrative user.
    *
diff --git a/core/modules/search/tests/src/Functional/SearchCommentCountToggleTest.php b/core/modules/search/tests/src/Functional/SearchCommentCountToggleTest.php
index 43f2a311343d..03520359ad50 100644
--- a/core/modules/search/tests/src/Functional/SearchCommentCountToggleTest.php
+++ b/core/modules/search/tests/src/Functional/SearchCommentCountToggleTest.php
@@ -27,6 +27,11 @@ class SearchCommentCountToggleTest extends BrowserTestBase {
    */
   protected static $modules = ['node', 'comment', 'search', 'dblog'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with permission to search and post comments.
    *
diff --git a/core/modules/search/tests/src/Functional/SearchCommentTest.php b/core/modules/search/tests/src/Functional/SearchCommentTest.php
index 3c57db0d06c5..c513be8d5379 100644
--- a/core/modules/search/tests/src/Functional/SearchCommentTest.php
+++ b/core/modules/search/tests/src/Functional/SearchCommentTest.php
@@ -26,6 +26,11 @@ class SearchCommentTest extends BrowserTestBase {
    */
   protected static $modules = ['filter', 'node', 'comment', 'search'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test subject for comments.
    *
diff --git a/core/modules/search/tests/src/Functional/SearchConfigSettingsFormTest.php b/core/modules/search/tests/src/Functional/SearchConfigSettingsFormTest.php
index f0c9422d6a80..fa334854870e 100644
--- a/core/modules/search/tests/src/Functional/SearchConfigSettingsFormTest.php
+++ b/core/modules/search/tests/src/Functional/SearchConfigSettingsFormTest.php
@@ -20,6 +20,11 @@ class SearchConfigSettingsFormTest extends BrowserTestBase {
    */
   protected static $modules = ['block', 'dblog', 'node', 'search', 'search_extra_type', 'test_page_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * User who can search and administer search.
    *
diff --git a/core/modules/search/tests/src/Functional/SearchDateIntervalTest.php b/core/modules/search/tests/src/Functional/SearchDateIntervalTest.php
index 84c2d38f00c9..22c19b9fd898 100644
--- a/core/modules/search/tests/src/Functional/SearchDateIntervalTest.php
+++ b/core/modules/search/tests/src/Functional/SearchDateIntervalTest.php
@@ -17,6 +17,11 @@ class SearchDateIntervalTest extends BrowserTestBase {
    */
   protected static $modules = ['language', 'search_date_query_alter', 'node', 'search'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/search/tests/src/Functional/SearchEmbedFormTest.php b/core/modules/search/tests/src/Functional/SearchEmbedFormTest.php
index c134093df6f2..80033b4de78b 100644
--- a/core/modules/search/tests/src/Functional/SearchEmbedFormTest.php
+++ b/core/modules/search/tests/src/Functional/SearchEmbedFormTest.php
@@ -16,6 +16,11 @@ class SearchEmbedFormTest extends BrowserTestBase {
    */
   protected static $modules = ['node', 'search', 'search_embedded_form'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Node used for testing.
    *
diff --git a/core/modules/search/tests/src/Functional/SearchExactTest.php b/core/modules/search/tests/src/Functional/SearchExactTest.php
index 05ad58cff976..1b77e703c2a8 100644
--- a/core/modules/search/tests/src/Functional/SearchExactTest.php
+++ b/core/modules/search/tests/src/Functional/SearchExactTest.php
@@ -16,6 +16,11 @@ class SearchExactTest extends BrowserTestBase {
    */
   protected static $modules = ['node', 'search'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that the correct number of pager links are found for both keywords and phrases.
    */
diff --git a/core/modules/search/tests/src/Functional/SearchKeywordsConditionsTest.php b/core/modules/search/tests/src/Functional/SearchKeywordsConditionsTest.php
index 4c946894d6d8..38faa34e55b5 100644
--- a/core/modules/search/tests/src/Functional/SearchKeywordsConditionsTest.php
+++ b/core/modules/search/tests/src/Functional/SearchKeywordsConditionsTest.php
@@ -21,6 +21,11 @@ class SearchKeywordsConditionsTest extends BrowserTestBase {
    */
   protected static $modules = ['comment', 'search', 'search_extra_type', 'test_page_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with permission to search and post comments.
    *
diff --git a/core/modules/search/tests/src/Functional/SearchLanguageTest.php b/core/modules/search/tests/src/Functional/SearchLanguageTest.php
index d884a4bbc4b1..539fac67ff3b 100644
--- a/core/modules/search/tests/src/Functional/SearchLanguageTest.php
+++ b/core/modules/search/tests/src/Functional/SearchLanguageTest.php
@@ -19,6 +19,11 @@ class SearchLanguageTest extends BrowserTestBase {
    */
   protected static $modules = ['language', 'node', 'search'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Array of nodes available to search.
    *
diff --git a/core/modules/search/tests/src/Functional/SearchMultilingualEntityTest.php b/core/modules/search/tests/src/Functional/SearchMultilingualEntityTest.php
index d823b2e63279..4377ef0b7551 100644
--- a/core/modules/search/tests/src/Functional/SearchMultilingualEntityTest.php
+++ b/core/modules/search/tests/src/Functional/SearchMultilingualEntityTest.php
@@ -34,6 +34,11 @@ class SearchMultilingualEntityTest extends BrowserTestBase {
    */
   protected static $modules = ['language', 'locale', 'comment', 'node', 'search'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/search/tests/src/Functional/SearchNodeDiacriticsTest.php b/core/modules/search/tests/src/Functional/SearchNodeDiacriticsTest.php
index e83d84b4ad72..2e7150d8d2d1 100644
--- a/core/modules/search/tests/src/Functional/SearchNodeDiacriticsTest.php
+++ b/core/modules/search/tests/src/Functional/SearchNodeDiacriticsTest.php
@@ -16,6 +16,11 @@ class SearchNodeDiacriticsTest extends BrowserTestBase {
    */
   protected static $modules = ['node', 'search'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with permission to use advanced search.
    *
diff --git a/core/modules/search/tests/src/Functional/SearchNodePunctuationTest.php b/core/modules/search/tests/src/Functional/SearchNodePunctuationTest.php
index c0c597ecc5f2..02945562a7d7 100644
--- a/core/modules/search/tests/src/Functional/SearchNodePunctuationTest.php
+++ b/core/modules/search/tests/src/Functional/SearchNodePunctuationTest.php
@@ -16,6 +16,11 @@ class SearchNodePunctuationTest extends BrowserTestBase {
    */
   protected static $modules = ['node', 'search'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with permission to use advanced search.
    *
diff --git a/core/modules/search/tests/src/Functional/SearchNodeUpdateAndDeletionTest.php b/core/modules/search/tests/src/Functional/SearchNodeUpdateAndDeletionTest.php
index 54095bd63625..6f2a4941ccee 100644
--- a/core/modules/search/tests/src/Functional/SearchNodeUpdateAndDeletionTest.php
+++ b/core/modules/search/tests/src/Functional/SearchNodeUpdateAndDeletionTest.php
@@ -18,6 +18,11 @@ class SearchNodeUpdateAndDeletionTest extends BrowserTestBase {
    */
   protected static $modules = ['node', 'search'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with permission to access and search content.
    *
diff --git a/core/modules/search/tests/src/Functional/SearchNumberMatchingTest.php b/core/modules/search/tests/src/Functional/SearchNumberMatchingTest.php
index 94eec22daa7a..8888b4ddc521 100644
--- a/core/modules/search/tests/src/Functional/SearchNumberMatchingTest.php
+++ b/core/modules/search/tests/src/Functional/SearchNumberMatchingTest.php
@@ -21,6 +21,11 @@ class SearchNumberMatchingTest extends BrowserTestBase {
    */
   protected static $modules = ['dblog', 'node', 'search'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with permission to administer nodes.
    *
diff --git a/core/modules/search/tests/src/Functional/SearchNumbersTest.php b/core/modules/search/tests/src/Functional/SearchNumbersTest.php
index 60c67394563b..43dd788d1776 100644
--- a/core/modules/search/tests/src/Functional/SearchNumbersTest.php
+++ b/core/modules/search/tests/src/Functional/SearchNumbersTest.php
@@ -21,6 +21,11 @@ class SearchNumbersTest extends BrowserTestBase {
    */
   protected static $modules = ['dblog', 'node', 'search'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with permission to administer nodes.
    *
diff --git a/core/modules/search/tests/src/Functional/SearchPageCacheTagsTest.php b/core/modules/search/tests/src/Functional/SearchPageCacheTagsTest.php
index 320833e51fa6..daa55efaee56 100644
--- a/core/modules/search/tests/src/Functional/SearchPageCacheTagsTest.php
+++ b/core/modules/search/tests/src/Functional/SearchPageCacheTagsTest.php
@@ -20,6 +20,11 @@ class SearchPageCacheTagsTest extends BrowserTestBase {
    */
   protected static $modules = ['node', 'search'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/search/tests/src/Functional/SearchPageOverrideTest.php b/core/modules/search/tests/src/Functional/SearchPageOverrideTest.php
index 5a614e30383b..2faac41a5a84 100644
--- a/core/modules/search/tests/src/Functional/SearchPageOverrideTest.php
+++ b/core/modules/search/tests/src/Functional/SearchPageOverrideTest.php
@@ -19,6 +19,11 @@ class SearchPageOverrideTest extends BrowserTestBase {
    */
   protected static $modules = ['search', 'search_extra_type'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with permission to administer search.
    *
diff --git a/core/modules/search/tests/src/Functional/SearchPageTextTest.php b/core/modules/search/tests/src/Functional/SearchPageTextTest.php
index d126bf92711a..148b4372ce76 100644
--- a/core/modules/search/tests/src/Functional/SearchPageTextTest.php
+++ b/core/modules/search/tests/src/Functional/SearchPageTextTest.php
@@ -18,6 +18,11 @@ class SearchPageTextTest extends BrowserTestBase {
    */
   protected static $modules = ['block', 'node', 'search'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with permission to use advanced search.
    *
diff --git a/core/modules/search/tests/src/Functional/SearchPreprocessLangcodeTest.php b/core/modules/search/tests/src/Functional/SearchPreprocessLangcodeTest.php
index 9f0b991484e0..cdbfb2f65270 100644
--- a/core/modules/search/tests/src/Functional/SearchPreprocessLangcodeTest.php
+++ b/core/modules/search/tests/src/Functional/SearchPreprocessLangcodeTest.php
@@ -16,6 +16,11 @@ class SearchPreprocessLangcodeTest extends BrowserTestBase {
    */
   protected static $modules = ['node', 'search', 'search_langcode_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test node for searching.
    *
diff --git a/core/modules/search/tests/src/Functional/SearchQueryAlterTest.php b/core/modules/search/tests/src/Functional/SearchQueryAlterTest.php
index e28d63d4aff8..bcfd7e2692de 100644
--- a/core/modules/search/tests/src/Functional/SearchQueryAlterTest.php
+++ b/core/modules/search/tests/src/Functional/SearchQueryAlterTest.php
@@ -16,6 +16,11 @@ class SearchQueryAlterTest extends BrowserTestBase {
    */
   protected static $modules = ['node', 'search', 'search_query_alter'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that the query alter works.
    */
diff --git a/core/modules/search/tests/src/Functional/SearchRankingTest.php b/core/modules/search/tests/src/Functional/SearchRankingTest.php
index 86c5ff656807..64eb1b776a00 100644
--- a/core/modules/search/tests/src/Functional/SearchRankingTest.php
+++ b/core/modules/search/tests/src/Functional/SearchRankingTest.php
@@ -35,6 +35,11 @@ class SearchRankingTest extends BrowserTestBase {
    */
   protected static $modules = ['node', 'search', 'statistics', 'comment'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/search/tests/src/Functional/SearchSetLocaleTest.php b/core/modules/search/tests/src/Functional/SearchSetLocaleTest.php
index 5dee65879f12..c0faabccef4a 100644
--- a/core/modules/search/tests/src/Functional/SearchSetLocaleTest.php
+++ b/core/modules/search/tests/src/Functional/SearchSetLocaleTest.php
@@ -16,6 +16,11 @@ class SearchSetLocaleTest extends BrowserTestBase {
    */
   protected static $modules = ['comment', 'node', 'search'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A node search plugin instance.
    *
diff --git a/core/modules/search/tests/src/Functional/SearchSimplifyTest.php b/core/modules/search/tests/src/Functional/SearchSimplifyTest.php
index a451063e0a74..127539ef742a 100644
--- a/core/modules/search/tests/src/Functional/SearchSimplifyTest.php
+++ b/core/modules/search/tests/src/Functional/SearchSimplifyTest.php
@@ -16,6 +16,11 @@ class SearchSimplifyTest extends BrowserTestBase {
    */
   protected static $modules = ['search'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that all Unicode characters simplify correctly.
    */
diff --git a/core/modules/search/tests/src/Functional/SearchTokenizerTest.php b/core/modules/search/tests/src/Functional/SearchTokenizerTest.php
index 2e608fc05633..8b906a72451b 100644
--- a/core/modules/search/tests/src/Functional/SearchTokenizerTest.php
+++ b/core/modules/search/tests/src/Functional/SearchTokenizerTest.php
@@ -16,6 +16,11 @@ class SearchTokenizerTest extends BrowserTestBase {
    */
   protected static $modules = ['search'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Verifies that strings of CJK characters are tokenized.
    *
diff --git a/core/modules/settings_tray/tests/src/Functional/SettingsTrayTest.php b/core/modules/settings_tray/tests/src/Functional/SettingsTrayTest.php
index aec0392de1de..2aa98363c632 100644
--- a/core/modules/settings_tray/tests/src/Functional/SettingsTrayTest.php
+++ b/core/modules/settings_tray/tests/src/Functional/SettingsTrayTest.php
@@ -20,6 +20,11 @@ class SettingsTrayTest extends BrowserTestBase {
     'settings_tray_test',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Gets the block CSS selector.
    *
diff --git a/core/modules/settings_tray/tests/src/FunctionalJavascript/ConfigAccessTest.php b/core/modules/settings_tray/tests/src/FunctionalJavascript/ConfigAccessTest.php
index 6b15be9425eb..c3e604a29f48 100644
--- a/core/modules/settings_tray/tests/src/FunctionalJavascript/ConfigAccessTest.php
+++ b/core/modules/settings_tray/tests/src/FunctionalJavascript/ConfigAccessTest.php
@@ -20,6 +20,11 @@ class ConfigAccessTest extends SettingsTrayTestBase {
     'menu_ui',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/settings_tray/tests/src/FunctionalJavascript/OverriddenConfigurationTest.php b/core/modules/settings_tray/tests/src/FunctionalJavascript/OverriddenConfigurationTest.php
index 97cd4db18f43..ec8afac59cf9 100644
--- a/core/modules/settings_tray/tests/src/FunctionalJavascript/OverriddenConfigurationTest.php
+++ b/core/modules/settings_tray/tests/src/FunctionalJavascript/OverriddenConfigurationTest.php
@@ -22,6 +22,11 @@ class OverriddenConfigurationTest extends SettingsTrayTestBase {
     'menu_link_content',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/settings_tray/tests/src/FunctionalJavascript/QuickEditIntegrationTest.php b/core/modules/settings_tray/tests/src/FunctionalJavascript/QuickEditIntegrationTest.php
index a543baf1262e..6ee2e51fd9af 100644
--- a/core/modules/settings_tray/tests/src/FunctionalJavascript/QuickEditIntegrationTest.php
+++ b/core/modules/settings_tray/tests/src/FunctionalJavascript/QuickEditIntegrationTest.php
@@ -22,6 +22,11 @@ class QuickEditIntegrationTest extends SettingsTrayTestBase {
     'quickedit',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/settings_tray/tests/src/FunctionalJavascript/SettingsTrayBlockFormTest.php b/core/modules/settings_tray/tests/src/FunctionalJavascript/SettingsTrayBlockFormTest.php
index be89b7c576d4..bad7a75d672a 100644
--- a/core/modules/settings_tray/tests/src/FunctionalJavascript/SettingsTrayBlockFormTest.php
+++ b/core/modules/settings_tray/tests/src/FunctionalJavascript/SettingsTrayBlockFormTest.php
@@ -23,6 +23,11 @@ class SettingsTrayBlockFormTest extends SettingsTrayTestBase {
     'settings_tray_test',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/shortcut/tests/src/Functional/Hal/ShortcutHalJsonAnonTest.php b/core/modules/shortcut/tests/src/Functional/Hal/ShortcutHalJsonAnonTest.php
index ba6c8a798d6a..6dd633b7e0d6 100644
--- a/core/modules/shortcut/tests/src/Functional/Hal/ShortcutHalJsonAnonTest.php
+++ b/core/modules/shortcut/tests/src/Functional/Hal/ShortcutHalJsonAnonTest.php
@@ -20,6 +20,11 @@ class ShortcutHalJsonAnonTest extends ShortcutResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/shortcut/tests/src/Functional/Hal/ShortcutHalJsonBasicAuthTest.php b/core/modules/shortcut/tests/src/Functional/Hal/ShortcutHalJsonBasicAuthTest.php
index 784c3ebc44eb..65923fdee342 100644
--- a/core/modules/shortcut/tests/src/Functional/Hal/ShortcutHalJsonBasicAuthTest.php
+++ b/core/modules/shortcut/tests/src/Functional/Hal/ShortcutHalJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class ShortcutHalJsonBasicAuthTest extends ShortcutHalJsonAnonTest {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/shortcut/tests/src/Functional/Hal/ShortcutHalJsonCookieTest.php b/core/modules/shortcut/tests/src/Functional/Hal/ShortcutHalJsonCookieTest.php
index 7b3b8348d944..01f152dd493b 100644
--- a/core/modules/shortcut/tests/src/Functional/Hal/ShortcutHalJsonCookieTest.php
+++ b/core/modules/shortcut/tests/src/Functional/Hal/ShortcutHalJsonCookieTest.php
@@ -15,4 +15,9 @@ class ShortcutHalJsonCookieTest extends ShortcutHalJsonAnonTest {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/shortcut/tests/src/Functional/Hal/ShortcutSetHalJsonAnonTest.php b/core/modules/shortcut/tests/src/Functional/Hal/ShortcutSetHalJsonAnonTest.php
index b3faae7fbaeb..4f1948059523 100644
--- a/core/modules/shortcut/tests/src/Functional/Hal/ShortcutSetHalJsonAnonTest.php
+++ b/core/modules/shortcut/tests/src/Functional/Hal/ShortcutSetHalJsonAnonTest.php
@@ -17,6 +17,11 @@ class ShortcutSetHalJsonAnonTest extends ShortcutSetResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/shortcut/tests/src/Functional/Hal/ShortcutSetHalJsonBasicAuthTest.php b/core/modules/shortcut/tests/src/Functional/Hal/ShortcutSetHalJsonBasicAuthTest.php
index d3a70574117a..5d7b70148925 100644
--- a/core/modules/shortcut/tests/src/Functional/Hal/ShortcutSetHalJsonBasicAuthTest.php
+++ b/core/modules/shortcut/tests/src/Functional/Hal/ShortcutSetHalJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class ShortcutSetHalJsonBasicAuthTest extends ShortcutSetHalJsonAnonTest {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/shortcut/tests/src/Functional/Hal/ShortcutSetHalJsonCookieTest.php b/core/modules/shortcut/tests/src/Functional/Hal/ShortcutSetHalJsonCookieTest.php
index 786936ef0887..9c8189965e24 100644
--- a/core/modules/shortcut/tests/src/Functional/Hal/ShortcutSetHalJsonCookieTest.php
+++ b/core/modules/shortcut/tests/src/Functional/Hal/ShortcutSetHalJsonCookieTest.php
@@ -16,4 +16,9 @@ class ShortcutSetHalJsonCookieTest extends ShortcutSetHalJsonAnonTest {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/shortcut/tests/src/Functional/Rest/ShortcutJsonAnonTest.php b/core/modules/shortcut/tests/src/Functional/Rest/ShortcutJsonAnonTest.php
index 04456fac29f1..114dc60d1d02 100644
--- a/core/modules/shortcut/tests/src/Functional/Rest/ShortcutJsonAnonTest.php
+++ b/core/modules/shortcut/tests/src/Functional/Rest/ShortcutJsonAnonTest.php
@@ -21,4 +21,9 @@ class ShortcutJsonAnonTest extends ShortcutResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/shortcut/tests/src/Functional/Rest/ShortcutJsonBasicAuthTest.php b/core/modules/shortcut/tests/src/Functional/Rest/ShortcutJsonBasicAuthTest.php
index e0859e3aa3fe..c36716e58c24 100644
--- a/core/modules/shortcut/tests/src/Functional/Rest/ShortcutJsonBasicAuthTest.php
+++ b/core/modules/shortcut/tests/src/Functional/Rest/ShortcutJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class ShortcutJsonBasicAuthTest extends ShortcutResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/shortcut/tests/src/Functional/Rest/ShortcutJsonCookieTest.php b/core/modules/shortcut/tests/src/Functional/Rest/ShortcutJsonCookieTest.php
index 7bf210225be5..fed029af8aa7 100644
--- a/core/modules/shortcut/tests/src/Functional/Rest/ShortcutJsonCookieTest.php
+++ b/core/modules/shortcut/tests/src/Functional/Rest/ShortcutJsonCookieTest.php
@@ -26,4 +26,9 @@ class ShortcutJsonCookieTest extends ShortcutResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/shortcut/tests/src/Functional/Rest/ShortcutSetJsonAnonTest.php b/core/modules/shortcut/tests/src/Functional/Rest/ShortcutSetJsonAnonTest.php
index 96750b57b19a..ce5f270a21c5 100644
--- a/core/modules/shortcut/tests/src/Functional/Rest/ShortcutSetJsonAnonTest.php
+++ b/core/modules/shortcut/tests/src/Functional/Rest/ShortcutSetJsonAnonTest.php
@@ -21,4 +21,9 @@ class ShortcutSetJsonAnonTest extends ShortcutSetResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/shortcut/tests/src/Functional/Rest/ShortcutSetJsonBasicAuthTest.php b/core/modules/shortcut/tests/src/Functional/Rest/ShortcutSetJsonBasicAuthTest.php
index 6ddaf54b0d9f..620f1f722066 100644
--- a/core/modules/shortcut/tests/src/Functional/Rest/ShortcutSetJsonBasicAuthTest.php
+++ b/core/modules/shortcut/tests/src/Functional/Rest/ShortcutSetJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class ShortcutSetJsonBasicAuthTest extends ShortcutSetResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/shortcut/tests/src/Functional/Rest/ShortcutSetJsonCookieTest.php b/core/modules/shortcut/tests/src/Functional/Rest/ShortcutSetJsonCookieTest.php
index 60fe84060642..11676fe190a6 100644
--- a/core/modules/shortcut/tests/src/Functional/Rest/ShortcutSetJsonCookieTest.php
+++ b/core/modules/shortcut/tests/src/Functional/Rest/ShortcutSetJsonCookieTest.php
@@ -26,4 +26,9 @@ class ShortcutSetJsonCookieTest extends ShortcutSetResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/shortcut/tests/src/Functional/Rest/ShortcutSetXmlAnonTest.php b/core/modules/shortcut/tests/src/Functional/Rest/ShortcutSetXmlAnonTest.php
index 75ad14efd47f..5dc659538fdf 100644
--- a/core/modules/shortcut/tests/src/Functional/Rest/ShortcutSetXmlAnonTest.php
+++ b/core/modules/shortcut/tests/src/Functional/Rest/ShortcutSetXmlAnonTest.php
@@ -23,4 +23,9 @@ class ShortcutSetXmlAnonTest extends ShortcutSetResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/shortcut/tests/src/Functional/Rest/ShortcutSetXmlBasicAuthTest.php b/core/modules/shortcut/tests/src/Functional/Rest/ShortcutSetXmlBasicAuthTest.php
index 50c6e71c23f8..67b32991d55e 100644
--- a/core/modules/shortcut/tests/src/Functional/Rest/ShortcutSetXmlBasicAuthTest.php
+++ b/core/modules/shortcut/tests/src/Functional/Rest/ShortcutSetXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class ShortcutSetXmlBasicAuthTest extends ShortcutSetResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/shortcut/tests/src/Functional/Rest/ShortcutSetXmlCookieTest.php b/core/modules/shortcut/tests/src/Functional/Rest/ShortcutSetXmlCookieTest.php
index 71dccd16c369..969fefbaa6db 100644
--- a/core/modules/shortcut/tests/src/Functional/Rest/ShortcutSetXmlCookieTest.php
+++ b/core/modules/shortcut/tests/src/Functional/Rest/ShortcutSetXmlCookieTest.php
@@ -28,4 +28,9 @@ class ShortcutSetXmlCookieTest extends ShortcutSetResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/shortcut/tests/src/Functional/Rest/ShortcutXmlAnonTest.php b/core/modules/shortcut/tests/src/Functional/Rest/ShortcutXmlAnonTest.php
index 56c5c681a3b8..ca58e8bfad97 100644
--- a/core/modules/shortcut/tests/src/Functional/Rest/ShortcutXmlAnonTest.php
+++ b/core/modules/shortcut/tests/src/Functional/Rest/ShortcutXmlAnonTest.php
@@ -23,4 +23,9 @@ class ShortcutXmlAnonTest extends ShortcutResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/shortcut/tests/src/Functional/Rest/ShortcutXmlBasicAuthTest.php b/core/modules/shortcut/tests/src/Functional/Rest/ShortcutXmlBasicAuthTest.php
index 9645aedaeaea..209de30ae70e 100644
--- a/core/modules/shortcut/tests/src/Functional/Rest/ShortcutXmlBasicAuthTest.php
+++ b/core/modules/shortcut/tests/src/Functional/Rest/ShortcutXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class ShortcutXmlBasicAuthTest extends ShortcutResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/shortcut/tests/src/Functional/Rest/ShortcutXmlCookieTest.php b/core/modules/shortcut/tests/src/Functional/Rest/ShortcutXmlCookieTest.php
index 899b51d88a03..d2c4af202110 100644
--- a/core/modules/shortcut/tests/src/Functional/Rest/ShortcutXmlCookieTest.php
+++ b/core/modules/shortcut/tests/src/Functional/Rest/ShortcutXmlCookieTest.php
@@ -28,4 +28,9 @@ class ShortcutXmlCookieTest extends ShortcutResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/shortcut/tests/src/Functional/ShortcutCacheTagsTest.php b/core/modules/shortcut/tests/src/Functional/ShortcutCacheTagsTest.php
index a2282b1ddfc8..71720d4442e4 100644
--- a/core/modules/shortcut/tests/src/Functional/ShortcutCacheTagsTest.php
+++ b/core/modules/shortcut/tests/src/Functional/ShortcutCacheTagsTest.php
@@ -20,6 +20,11 @@ class ShortcutCacheTagsTest extends EntityCacheTagsTestBase {
    */
   public static $modules = ['shortcut'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/shortcut/tests/src/Functional/ShortcutLinksTest.php b/core/modules/shortcut/tests/src/Functional/ShortcutLinksTest.php
index aa6a5432b1ef..8f7bf0aa1bc7 100644
--- a/core/modules/shortcut/tests/src/Functional/ShortcutLinksTest.php
+++ b/core/modules/shortcut/tests/src/Functional/ShortcutLinksTest.php
@@ -28,6 +28,11 @@ class ShortcutLinksTest extends ShortcutTestBase {
    */
   public static $modules = ['router_test', 'views', 'block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/shortcut/tests/src/Functional/ShortcutSetsTest.php b/core/modules/shortcut/tests/src/Functional/ShortcutSetsTest.php
index 5db2f939891e..7b4fcc76acdc 100644
--- a/core/modules/shortcut/tests/src/Functional/ShortcutSetsTest.php
+++ b/core/modules/shortcut/tests/src/Functional/ShortcutSetsTest.php
@@ -18,6 +18,11 @@ class ShortcutSetsTest extends ShortcutTestBase {
    */
   public static $modules = ['block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/shortcut/tests/src/Functional/ShortcutTranslationUITest.php b/core/modules/shortcut/tests/src/Functional/ShortcutTranslationUITest.php
index e3308bd874d7..252d2d0224d4 100644
--- a/core/modules/shortcut/tests/src/Functional/ShortcutTranslationUITest.php
+++ b/core/modules/shortcut/tests/src/Functional/ShortcutTranslationUITest.php
@@ -32,6 +32,11 @@ class ShortcutTranslationUITest extends ContentTranslationUITestBase {
     'toolbar',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/simpletest/tests/src/Functional/SimpletestTest.php b/core/modules/simpletest/tests/src/Functional/SimpletestTest.php
index a7f634deb0fd..781a1bae30ac 100644
--- a/core/modules/simpletest/tests/src/Functional/SimpletestTest.php
+++ b/core/modules/simpletest/tests/src/Functional/SimpletestTest.php
@@ -18,6 +18,11 @@ class SimpletestTest extends BrowserTestBase {
    */
   public static $modules = ['simpletest'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test that we can uninstall the module without mishap.
    *
diff --git a/core/modules/statistics/tests/src/Functional/StatisticsAdminTest.php b/core/modules/statistics/tests/src/Functional/StatisticsAdminTest.php
index 5efc804b8826..cafdf9bbae03 100644
--- a/core/modules/statistics/tests/src/Functional/StatisticsAdminTest.php
+++ b/core/modules/statistics/tests/src/Functional/StatisticsAdminTest.php
@@ -22,6 +22,11 @@ class StatisticsAdminTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'statistics'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user that has permission to administer statistics.
    *
diff --git a/core/modules/statistics/tests/src/Functional/StatisticsAttachedTest.php b/core/modules/statistics/tests/src/Functional/StatisticsAttachedTest.php
index 42f1a225e5a9..9a77f50e06c3 100644
--- a/core/modules/statistics/tests/src/Functional/StatisticsAttachedTest.php
+++ b/core/modules/statistics/tests/src/Functional/StatisticsAttachedTest.php
@@ -19,6 +19,11 @@ class StatisticsAttachedTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'statistics'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/statistics/tests/src/Functional/StatisticsLoggingTest.php b/core/modules/statistics/tests/src/Functional/StatisticsLoggingTest.php
index cfba14e017ad..07abf5fdbcbd 100644
--- a/core/modules/statistics/tests/src/Functional/StatisticsLoggingTest.php
+++ b/core/modules/statistics/tests/src/Functional/StatisticsLoggingTest.php
@@ -23,6 +23,11 @@ class StatisticsLoggingTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'statistics', 'block', 'locale'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * User with permissions to create and edit pages.
    *
diff --git a/core/modules/statistics/tests/src/Functional/StatisticsReportsTest.php b/core/modules/statistics/tests/src/Functional/StatisticsReportsTest.php
index f0448110fd47..0b80251d6cf6 100644
--- a/core/modules/statistics/tests/src/Functional/StatisticsReportsTest.php
+++ b/core/modules/statistics/tests/src/Functional/StatisticsReportsTest.php
@@ -15,6 +15,11 @@ class StatisticsReportsTest extends StatisticsTestBase {
 
   use AssertPageCacheContextsAndTagsTrait;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the "popular content" block.
    */
diff --git a/core/modules/statistics/tests/src/Functional/StatisticsTokenReplaceTest.php b/core/modules/statistics/tests/src/Functional/StatisticsTokenReplaceTest.php
index 7e99ab3c800d..6a6709881527 100644
--- a/core/modules/statistics/tests/src/Functional/StatisticsTokenReplaceTest.php
+++ b/core/modules/statistics/tests/src/Functional/StatisticsTokenReplaceTest.php
@@ -12,6 +12,11 @@
  */
 class StatisticsTokenReplaceTest extends StatisticsTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Creates a node, then tests the statistics tokens generated from it.
    */
diff --git a/core/modules/statistics/tests/src/Functional/Views/IntegrationTest.php b/core/modules/statistics/tests/src/Functional/Views/IntegrationTest.php
index 16018206443b..ebee1ee43d2c 100644
--- a/core/modules/statistics/tests/src/Functional/Views/IntegrationTest.php
+++ b/core/modules/statistics/tests/src/Functional/Views/IntegrationTest.php
@@ -21,6 +21,11 @@ class IntegrationTest extends ViewTestBase {
    */
   public static $modules = ['statistics', 'statistics_test_views', 'node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Stores the user object that accesses the page.
    *
diff --git a/core/modules/statistics/tests/src/FunctionalJavascript/StatisticsLoggingTest.php b/core/modules/statistics/tests/src/FunctionalJavascript/StatisticsLoggingTest.php
index acd103e9f69d..c1b7bff29643 100644
--- a/core/modules/statistics/tests/src/FunctionalJavascript/StatisticsLoggingTest.php
+++ b/core/modules/statistics/tests/src/FunctionalJavascript/StatisticsLoggingTest.php
@@ -19,6 +19,11 @@ class StatisticsLoggingTest extends WebDriverTestBase {
    */
   public static $modules = ['node', 'statistics', 'language'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Node for tests.
    *
diff --git a/core/modules/syslog/tests/src/Functional/SyslogTest.php b/core/modules/syslog/tests/src/Functional/SyslogTest.php
index 11b577f2f242..8348cb1ee27a 100644
--- a/core/modules/syslog/tests/src/Functional/SyslogTest.php
+++ b/core/modules/syslog/tests/src/Functional/SyslogTest.php
@@ -18,6 +18,11 @@ class SyslogTest extends BrowserTestBase {
    */
   public static $modules = ['syslog'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the syslog settings page.
    */
diff --git a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestBundleHalJsonAnonTest.php b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestBundleHalJsonAnonTest.php
index 77988aa037a6..2802bee92850 100644
--- a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestBundleHalJsonAnonTest.php
+++ b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestBundleHalJsonAnonTest.php
@@ -19,6 +19,11 @@ class EntityTestBundleHalJsonAnonTest extends EntityTestBundleResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestBundleHalJsonBasicAuthTest.php b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestBundleHalJsonBasicAuthTest.php
index 47e44d2d1886..0557bfe74098 100644
--- a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestBundleHalJsonBasicAuthTest.php
+++ b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestBundleHalJsonBasicAuthTest.php
@@ -17,6 +17,11 @@ class EntityTestBundleHalJsonBasicAuthTest extends EntityTestBundleResourceTestB
    */
   public static $modules = ['hal', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestBundleHalJsonCookieTest.php b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestBundleHalJsonCookieTest.php
index 3e8b442de7a2..c604aa900eae 100644
--- a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestBundleHalJsonCookieTest.php
+++ b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestBundleHalJsonCookieTest.php
@@ -17,6 +17,11 @@ class EntityTestBundleHalJsonCookieTest extends EntityTestBundleResourceTestBase
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestHalJsonAnonTest.php b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestHalJsonAnonTest.php
index c272a1aa6fd6..17a65df4ca99 100644
--- a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestHalJsonAnonTest.php
+++ b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestHalJsonAnonTest.php
@@ -22,6 +22,11 @@ class EntityTestHalJsonAnonTest extends EntityTestResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestHalJsonBasicAuthTest.php b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestHalJsonBasicAuthTest.php
index 18fad4beede4..faef8d1cfc1c 100644
--- a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestHalJsonBasicAuthTest.php
+++ b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestHalJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class EntityTestHalJsonBasicAuthTest extends EntityTestHalJsonAnonTest {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestHalJsonCookieTest.php b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestHalJsonCookieTest.php
index bee58edc395e..10bf4a1ca2cc 100644
--- a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestHalJsonCookieTest.php
+++ b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestHalJsonCookieTest.php
@@ -16,4 +16,9 @@ class EntityTestHalJsonCookieTest extends EntityTestHalJsonAnonTest {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestHalJsonInternalPropertyNormalizerTest.php b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestHalJsonInternalPropertyNormalizerTest.php
index 73d70d3ff6a2..d68315ceb853 100644
--- a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestHalJsonInternalPropertyNormalizerTest.php
+++ b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestHalJsonInternalPropertyNormalizerTest.php
@@ -22,6 +22,11 @@ class EntityTestHalJsonInternalPropertyNormalizerTest extends EntityTestHalJsonA
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestLabelHalJsonAnonTest.php b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestLabelHalJsonAnonTest.php
index ca6e39535146..22c621205049 100644
--- a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestLabelHalJsonAnonTest.php
+++ b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestLabelHalJsonAnonTest.php
@@ -20,6 +20,11 @@ class EntityTestLabelHalJsonAnonTest extends EntityTestLabelResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestLabelHalJsonBasicAuthTest.php b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestLabelHalJsonBasicAuthTest.php
index dfae2e40243b..4af4063cb5fe 100644
--- a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestLabelHalJsonBasicAuthTest.php
+++ b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestLabelHalJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class EntityTestLabelHalJsonBasicAuthTest extends EntityTestLabelHalJsonAnonTest
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestLabelHalJsonCookieTest.php b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestLabelHalJsonCookieTest.php
index 3e373404e90f..f46f586a35e2 100644
--- a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestLabelHalJsonCookieTest.php
+++ b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestLabelHalJsonCookieTest.php
@@ -16,4 +16,9 @@ class EntityTestLabelHalJsonCookieTest extends EntityTestLabelHalJsonAnonTest {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestMapFieldHalJsonAnonTest.php b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestMapFieldHalJsonAnonTest.php
index af1ef4ceaa86..dfee26fbd619 100644
--- a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestMapFieldHalJsonAnonTest.php
+++ b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Hal/EntityTestMapFieldHalJsonAnonTest.php
@@ -20,6 +20,11 @@ class EntityTestMapFieldHalJsonAnonTest extends EntityTestMapFieldResourceTestBa
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestBundleJsonAnonTest.php b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestBundleJsonAnonTest.php
index 08eb70047b7c..c1abebd0b342 100644
--- a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestBundleJsonAnonTest.php
+++ b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestBundleJsonAnonTest.php
@@ -21,4 +21,9 @@ class EntityTestBundleJsonAnonTest extends EntityTestBundleResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestBundleJsonBasicAuthTest.php b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestBundleJsonBasicAuthTest.php
index d1a7adbc9e75..a6a437ada458 100644
--- a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestBundleJsonBasicAuthTest.php
+++ b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestBundleJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class EntityTestBundleJsonBasicAuthTest extends EntityTestBundleResourceTestBase
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestBundleJsonCookieTest.php b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestBundleJsonCookieTest.php
index 313c9b990804..b239f41efc82 100644
--- a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestBundleJsonCookieTest.php
+++ b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestBundleJsonCookieTest.php
@@ -26,4 +26,9 @@ class EntityTestBundleJsonCookieTest extends EntityTestBundleResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestBundleXmlAnonTest.php b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestBundleXmlAnonTest.php
index e88314b42554..8c2d234da2d7 100644
--- a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestBundleXmlAnonTest.php
+++ b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestBundleXmlAnonTest.php
@@ -23,4 +23,9 @@ class EntityTestBundleXmlAnonTest extends EntityTestBundleResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestBundleXmlBasicAuthTest.php b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestBundleXmlBasicAuthTest.php
index 701c15ba9f5b..059ca8efbd2c 100644
--- a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestBundleXmlBasicAuthTest.php
+++ b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestBundleXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class EntityTestBundleXmlBasicAuthTest extends EntityTestBundleResourceTestBase
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestBundleXmlCookieTest.php b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestBundleXmlCookieTest.php
index 2f3ee3310c8c..5252b3f35121 100644
--- a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestBundleXmlCookieTest.php
+++ b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestBundleXmlCookieTest.php
@@ -28,4 +28,9 @@ class EntityTestBundleXmlCookieTest extends EntityTestBundleResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestJsonAnonTest.php b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestJsonAnonTest.php
index 58d15b3aa2c7..ff36b51b43fa 100644
--- a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestJsonAnonTest.php
+++ b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestJsonAnonTest.php
@@ -23,4 +23,9 @@ class EntityTestJsonAnonTest extends EntityTestResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestJsonBasicAuthTest.php b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestJsonBasicAuthTest.php
index cd647e8fe3aa..b79bf3cf0393 100644
--- a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestJsonBasicAuthTest.php
+++ b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class EntityTestJsonBasicAuthTest extends EntityTestResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestJsonCookieTest.php b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestJsonCookieTest.php
index b76de42b3bf5..9ddb7a700072 100644
--- a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestJsonCookieTest.php
+++ b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestJsonCookieTest.php
@@ -26,4 +26,9 @@ class EntityTestJsonCookieTest extends EntityTestResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestJsonInternalPropertyNormalizerTest.php b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestJsonInternalPropertyNormalizerTest.php
index 7ac9d8985268..ec7868ec47c7 100644
--- a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestJsonInternalPropertyNormalizerTest.php
+++ b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestJsonInternalPropertyNormalizerTest.php
@@ -26,6 +26,11 @@ class EntityTestJsonInternalPropertyNormalizerTest extends EntityTestResourceTes
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestLabelJsonAnonTest.php b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestLabelJsonAnonTest.php
index 31a476de39ca..a122830c99f8 100644
--- a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestLabelJsonAnonTest.php
+++ b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestLabelJsonAnonTest.php
@@ -21,4 +21,9 @@ class EntityTestLabelJsonAnonTest extends EntityTestLabelResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestLabelJsonBasicAuthTest.php b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestLabelJsonBasicAuthTest.php
index 61cfea15b229..1332774b4f48 100644
--- a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestLabelJsonBasicAuthTest.php
+++ b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestLabelJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class EntityTestLabelJsonBasicAuthTest extends EntityTestLabelResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestLabelJsonCookieTest.php b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestLabelJsonCookieTest.php
index 20bb70184f43..5a6153f45c67 100644
--- a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestLabelJsonCookieTest.php
+++ b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestLabelJsonCookieTest.php
@@ -26,4 +26,9 @@ class EntityTestLabelJsonCookieTest extends EntityTestLabelResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestLabelXmlAnonTest.php b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestLabelXmlAnonTest.php
index ac1bd8685c33..dc6697698860 100644
--- a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestLabelXmlAnonTest.php
+++ b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestLabelXmlAnonTest.php
@@ -23,4 +23,9 @@ class EntityTestLabelXmlAnonTest extends EntityTestLabelResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestLabelXmlBasicAuthTest.php b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestLabelXmlBasicAuthTest.php
index e671098f2fa3..067780894f36 100644
--- a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestLabelXmlBasicAuthTest.php
+++ b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestLabelXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class EntityTestLabelXmlBasicAuthTest extends EntityTestLabelResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestLabelXmlCookieTest.php b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestLabelXmlCookieTest.php
index f859c7ff8b52..5aef8f7466ef 100644
--- a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestLabelXmlCookieTest.php
+++ b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestLabelXmlCookieTest.php
@@ -28,4 +28,9 @@ class EntityTestLabelXmlCookieTest extends EntityTestLabelResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestMapFieldJsonAnonTest.php b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestMapFieldJsonAnonTest.php
index 044068032557..5751c63f54d2 100644
--- a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestMapFieldJsonAnonTest.php
+++ b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestMapFieldJsonAnonTest.php
@@ -21,4 +21,9 @@ class EntityTestMapFieldJsonAnonTest extends EntityTestMapFieldResourceTestBase
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestTextItemNormalizerTest.php b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestTextItemNormalizerTest.php
index 3ae0044aee4c..9c3b978cc422 100644
--- a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestTextItemNormalizerTest.php
+++ b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestTextItemNormalizerTest.php
@@ -19,6 +19,11 @@ class EntityTestTextItemNormalizerTest extends EntityTestResourceTestBase {
    */
   public static $modules = ['filter_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestXmlAnonTest.php b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestXmlAnonTest.php
index a5548f9a78b1..1ddd84f81790 100644
--- a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestXmlAnonTest.php
+++ b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestXmlAnonTest.php
@@ -25,4 +25,9 @@ class EntityTestXmlAnonTest extends EntityTestResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestXmlBasicAuthTest.php b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestXmlBasicAuthTest.php
index d0501afb97b3..71f0e81fdac9 100644
--- a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestXmlBasicAuthTest.php
+++ b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class EntityTestXmlBasicAuthTest extends EntityTestResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestXmlCookieTest.php b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestXmlCookieTest.php
index 7fe4930fcb26..2fe9035233e0 100644
--- a/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestXmlCookieTest.php
+++ b/core/modules/system/tests/modules/entity_test/tests/src/Functional/Rest/EntityTestXmlCookieTest.php
@@ -28,4 +28,9 @@ class EntityTestXmlCookieTest extends EntityTestResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/system/tests/src/Functional/Ajax/FrameworkTest.php b/core/modules/system/tests/src/Functional/Ajax/FrameworkTest.php
index cc7b782d5114..077c237af56e 100644
--- a/core/modules/system/tests/src/Functional/Ajax/FrameworkTest.php
+++ b/core/modules/system/tests/src/Functional/Ajax/FrameworkTest.php
@@ -20,6 +20,11 @@
  */
 class FrameworkTest extends BrowserTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Ajax/OffCanvasDialogTest.php b/core/modules/system/tests/src/Functional/Ajax/OffCanvasDialogTest.php
index c7867221231a..919e1e7925d0 100644
--- a/core/modules/system/tests/src/Functional/Ajax/OffCanvasDialogTest.php
+++ b/core/modules/system/tests/src/Functional/Ajax/OffCanvasDialogTest.php
@@ -14,6 +14,11 @@
  */
 class OffCanvasDialogTest extends BrowserTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Modules to enable.
    *
diff --git a/core/modules/system/tests/src/Functional/Batch/PageTest.php b/core/modules/system/tests/src/Functional/Batch/PageTest.php
index b979eee4129f..239b40c515f5 100644
--- a/core/modules/system/tests/src/Functional/Batch/PageTest.php
+++ b/core/modules/system/tests/src/Functional/Batch/PageTest.php
@@ -18,6 +18,11 @@ class PageTest extends BrowserTestBase {
    */
   public static $modules = ['batch_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that the batch API progress page uses the correct theme.
    */
diff --git a/core/modules/system/tests/src/Functional/Batch/ProcessingTest.php b/core/modules/system/tests/src/Functional/Batch/ProcessingTest.php
index 97dc6e7a5f69..bba551189cd8 100644
--- a/core/modules/system/tests/src/Functional/Batch/ProcessingTest.php
+++ b/core/modules/system/tests/src/Functional/Batch/ProcessingTest.php
@@ -19,6 +19,11 @@ class ProcessingTest extends BrowserTestBase {
    */
   public static $modules = ['batch_test', 'test_page_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Tests batches triggered outside of form submission.
    */
diff --git a/core/modules/system/tests/src/Functional/Bootstrap/DrupalMessengerServiceTest.php b/core/modules/system/tests/src/Functional/Bootstrap/DrupalMessengerServiceTest.php
index 51404ef18d17..56db87601fc1 100644
--- a/core/modules/system/tests/src/Functional/Bootstrap/DrupalMessengerServiceTest.php
+++ b/core/modules/system/tests/src/Functional/Bootstrap/DrupalMessengerServiceTest.php
@@ -19,6 +19,11 @@ class DrupalMessengerServiceTest extends BrowserTestBase {
    */
   public static $modules = ['system_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests Messenger service.
    */
diff --git a/core/modules/system/tests/src/Functional/Cache/ClearTest.php b/core/modules/system/tests/src/Functional/Cache/ClearTest.php
index 905f010759e8..fe4add638868 100644
--- a/core/modules/system/tests/src/Functional/Cache/ClearTest.php
+++ b/core/modules/system/tests/src/Functional/Cache/ClearTest.php
@@ -12,6 +12,11 @@
 
 class ClearTest extends CacheTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     $this->defaultBin = 'render';
     $this->defaultValue = $this->randomMachineName(10);
diff --git a/core/modules/system/tests/src/Functional/Cache/SessionExistsCacheContextTest.php b/core/modules/system/tests/src/Functional/Cache/SessionExistsCacheContextTest.php
index 78fb983a612c..23ad7abaa18c 100644
--- a/core/modules/system/tests/src/Functional/Cache/SessionExistsCacheContextTest.php
+++ b/core/modules/system/tests/src/Functional/Cache/SessionExistsCacheContextTest.php
@@ -19,6 +19,11 @@ class SessionExistsCacheContextTest extends BrowserTestBase {
    */
   public static $modules = ['session_exists_cache_context_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests \Drupal\Core\Cache\Context\SessionExistsCacheContext::getContext().
    */
diff --git a/core/modules/system/tests/src/Functional/Common/AlterTest.php b/core/modules/system/tests/src/Functional/Common/AlterTest.php
index 00b6e5be452d..e96dd4c2da33 100644
--- a/core/modules/system/tests/src/Functional/Common/AlterTest.php
+++ b/core/modules/system/tests/src/Functional/Common/AlterTest.php
@@ -18,6 +18,11 @@ class AlterTest extends BrowserTestBase {
    */
   public static $modules = ['block', 'common_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests if the theme has been altered.
    */
diff --git a/core/modules/system/tests/src/Functional/Common/EarlyRenderingControllerTest.php b/core/modules/system/tests/src/Functional/Common/EarlyRenderingControllerTest.php
index 9d6c0af5d10b..9595abbfaf7b 100644
--- a/core/modules/system/tests/src/Functional/Common/EarlyRenderingControllerTest.php
+++ b/core/modules/system/tests/src/Functional/Common/EarlyRenderingControllerTest.php
@@ -22,6 +22,11 @@ class EarlyRenderingControllerTest extends BrowserTestBase {
    */
   public static $modules = ['system', 'early_rendering_controller_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests theme preprocess functions being able to attach assets.
    */
diff --git a/core/modules/system/tests/src/Functional/Common/FormatDateTest.php b/core/modules/system/tests/src/Functional/Common/FormatDateTest.php
index a595db77809d..b2ff7b1a00e1 100644
--- a/core/modules/system/tests/src/Functional/Common/FormatDateTest.php
+++ b/core/modules/system/tests/src/Functional/Common/FormatDateTest.php
@@ -11,6 +11,11 @@
  */
 class FormatDateTest extends BrowserTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests admin-defined formats in DateFormatterInterface::format().
    */
diff --git a/core/modules/system/tests/src/Functional/Common/RenderWebTest.php b/core/modules/system/tests/src/Functional/Common/RenderWebTest.php
index 65d260403912..5e64bfa92c29 100644
--- a/core/modules/system/tests/src/Functional/Common/RenderWebTest.php
+++ b/core/modules/system/tests/src/Functional/Common/RenderWebTest.php
@@ -23,6 +23,11 @@ class RenderWebTest extends BrowserTestBase {
    */
   public static $modules = ['common_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Asserts the cache context for the wrapper format is always present.
    */
diff --git a/core/modules/system/tests/src/Functional/Common/UrlTest.php b/core/modules/system/tests/src/Functional/Common/UrlTest.php
index bdddea572c73..d304e122e0ac 100644
--- a/core/modules/system/tests/src/Functional/Common/UrlTest.php
+++ b/core/modules/system/tests/src/Functional/Common/UrlTest.php
@@ -24,6 +24,11 @@ class UrlTest extends BrowserTestBase {
 
   public static $modules = ['common_test', 'url_alter_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Confirms that invalid URLs are filtered in link generating functions.
    */
diff --git a/core/modules/system/tests/src/Functional/Condition/ConditionFormTest.php b/core/modules/system/tests/src/Functional/Condition/ConditionFormTest.php
index adefc4392e62..2cdaabeb3ee0 100644
--- a/core/modules/system/tests/src/Functional/Condition/ConditionFormTest.php
+++ b/core/modules/system/tests/src/Functional/Condition/ConditionFormTest.php
@@ -18,6 +18,11 @@ class ConditionFormTest extends BrowserTestBase {
 
   public static $modules = ['node', 'condition_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Submit the condition_node_type_test_form to test condition forms.
    */
diff --git a/core/modules/system/tests/src/Functional/CsrfRequestHeaderTest.php b/core/modules/system/tests/src/Functional/CsrfRequestHeaderTest.php
index 0bb9016c4819..9707141734bb 100644
--- a/core/modules/system/tests/src/Functional/CsrfRequestHeaderTest.php
+++ b/core/modules/system/tests/src/Functional/CsrfRequestHeaderTest.php
@@ -19,6 +19,11 @@ class CsrfRequestHeaderTest extends BrowserTestBase {
    */
   public static $modules = ['system', 'csrf_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests access to routes protected by CSRF request header requirements.
    *
diff --git a/core/modules/system/tests/src/Functional/Database/SelectPagerDefaultTest.php b/core/modules/system/tests/src/Functional/Database/SelectPagerDefaultTest.php
index e4e83d2d9fed..a38a5f0180f3 100644
--- a/core/modules/system/tests/src/Functional/Database/SelectPagerDefaultTest.php
+++ b/core/modules/system/tests/src/Functional/Database/SelectPagerDefaultTest.php
@@ -13,6 +13,11 @@
  */
 class SelectPagerDefaultTest extends DatabaseTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Confirms that a pager query returns the correct results.
    *
diff --git a/core/modules/system/tests/src/Functional/Database/SelectTableSortDefaultTest.php b/core/modules/system/tests/src/Functional/Database/SelectTableSortDefaultTest.php
index ee69dec94589..7e2e2e9a676f 100644
--- a/core/modules/system/tests/src/Functional/Database/SelectTableSortDefaultTest.php
+++ b/core/modules/system/tests/src/Functional/Database/SelectTableSortDefaultTest.php
@@ -11,6 +11,11 @@
  */
 class SelectTableSortDefaultTest extends DatabaseTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Confirms that a tablesort query returns the correct results.
    *
diff --git a/core/modules/system/tests/src/Functional/Database/TemporaryQueryTest.php b/core/modules/system/tests/src/Functional/Database/TemporaryQueryTest.php
index f44073571a8c..c31b96bb5b98 100644
--- a/core/modules/system/tests/src/Functional/Database/TemporaryQueryTest.php
+++ b/core/modules/system/tests/src/Functional/Database/TemporaryQueryTest.php
@@ -16,6 +16,11 @@ class TemporaryQueryTest extends DatabaseTestBase {
    */
   public static $modules = ['database_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Returns the number of rows of a table.
    */
diff --git a/core/modules/system/tests/src/Functional/Datetime/DrupalDateTimeTest.php b/core/modules/system/tests/src/Functional/Datetime/DrupalDateTimeTest.php
index 6843e54f7537..cb57699c5f1e 100644
--- a/core/modules/system/tests/src/Functional/Datetime/DrupalDateTimeTest.php
+++ b/core/modules/system/tests/src/Functional/Datetime/DrupalDateTimeTest.php
@@ -18,6 +18,11 @@ class DrupalDateTimeTest extends BrowserTestBase {
    */
   public static $modules = [];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test setup.
    */
diff --git a/core/modules/system/tests/src/Functional/DrupalKernel/ContainerRebuildWebTest.php b/core/modules/system/tests/src/Functional/DrupalKernel/ContainerRebuildWebTest.php
index 828b92f28913..93deab12b8e0 100644
--- a/core/modules/system/tests/src/Functional/DrupalKernel/ContainerRebuildWebTest.php
+++ b/core/modules/system/tests/src/Functional/DrupalKernel/ContainerRebuildWebTest.php
@@ -16,6 +16,11 @@ class ContainerRebuildWebTest extends BrowserTestBase {
    */
   public static $modules = ['service_provider_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Sets a different deployment identifier.
    */
diff --git a/core/modules/system/tests/src/Functional/DrupalKernel/ContentNegotiationTest.php b/core/modules/system/tests/src/Functional/DrupalKernel/ContentNegotiationTest.php
index 58157369b3db..a57b941e2342 100644
--- a/core/modules/system/tests/src/Functional/DrupalKernel/ContentNegotiationTest.php
+++ b/core/modules/system/tests/src/Functional/DrupalKernel/ContentNegotiationTest.php
@@ -11,6 +11,11 @@
  */
 class ContentNegotiationTest extends BrowserTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Verifies HTML responses for bogus Accept headers.
    *
diff --git a/core/modules/system/tests/src/Functional/Entity/EntityAddUITest.php b/core/modules/system/tests/src/Functional/Entity/EntityAddUITest.php
index a16614f1460f..3e8d187dbe0d 100644
--- a/core/modules/system/tests/src/Functional/Entity/EntityAddUITest.php
+++ b/core/modules/system/tests/src/Functional/Entity/EntityAddUITest.php
@@ -19,6 +19,11 @@ class EntityAddUITest extends BrowserTestBase {
    */
   public static $modules = ['entity_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the add page for an entity type using bundle entities.
    */
diff --git a/core/modules/system/tests/src/Functional/Entity/EntityFormTest.php b/core/modules/system/tests/src/Functional/Entity/EntityFormTest.php
index 7b497bf417f2..f6bd340dbb19 100644
--- a/core/modules/system/tests/src/Functional/Entity/EntityFormTest.php
+++ b/core/modules/system/tests/src/Functional/Entity/EntityFormTest.php
@@ -20,6 +20,11 @@ class EntityFormTest extends BrowserTestBase {
    */
   public static $modules = ['entity_test', 'language'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     $web_user = $this->drupalCreateUser(['administer entity_test content', 'view test entity']);
diff --git a/core/modules/system/tests/src/Functional/Entity/EntityListBuilderTest.php b/core/modules/system/tests/src/Functional/Entity/EntityListBuilderTest.php
index dec8dd8c7133..5a03e80ef809 100644
--- a/core/modules/system/tests/src/Functional/Entity/EntityListBuilderTest.php
+++ b/core/modules/system/tests/src/Functional/Entity/EntityListBuilderTest.php
@@ -18,6 +18,11 @@ class EntityListBuilderTest extends BrowserTestBase {
    */
   public static $modules = ['entity_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Entity/EntityOperationsTest.php b/core/modules/system/tests/src/Functional/Entity/EntityOperationsTest.php
index f881a94bb5b7..07d58b6517da 100644
--- a/core/modules/system/tests/src/Functional/Entity/EntityOperationsTest.php
+++ b/core/modules/system/tests/src/Functional/Entity/EntityOperationsTest.php
@@ -19,6 +19,11 @@ class EntityOperationsTest extends BrowserTestBase {
    */
   public static $modules = ['entity_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/system/tests/src/Functional/Entity/EntityRevisionsTest.php b/core/modules/system/tests/src/Functional/Entity/EntityRevisionsTest.php
index efc5a82386be..18bfc1824978 100644
--- a/core/modules/system/tests/src/Functional/Entity/EntityRevisionsTest.php
+++ b/core/modules/system/tests/src/Functional/Entity/EntityRevisionsTest.php
@@ -24,6 +24,11 @@ class EntityRevisionsTest extends BrowserTestBase {
    */
   public static $modules = ['entity_test', 'language'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with permission to administer entity_test content.
    *
diff --git a/core/modules/system/tests/src/Functional/Entity/EntityTranslationFormTest.php b/core/modules/system/tests/src/Functional/Entity/EntityTranslationFormTest.php
index e008e71e1f98..a4472405e524 100644
--- a/core/modules/system/tests/src/Functional/Entity/EntityTranslationFormTest.php
+++ b/core/modules/system/tests/src/Functional/Entity/EntityTranslationFormTest.php
@@ -21,6 +21,11 @@ class EntityTranslationFormTest extends BrowserTestBase {
    */
   public static $modules = ['entity_test', 'language', 'node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected $langcodes;
 
   protected function setUp() {
diff --git a/core/modules/system/tests/src/Functional/Entity/EntityViewControllerTest.php b/core/modules/system/tests/src/Functional/Entity/EntityViewControllerTest.php
index 3bd84036864a..bdc63f2dbc79 100644
--- a/core/modules/system/tests/src/Functional/Entity/EntityViewControllerTest.php
+++ b/core/modules/system/tests/src/Functional/Entity/EntityViewControllerTest.php
@@ -19,6 +19,11 @@ class EntityViewControllerTest extends BrowserTestBase {
    */
   public static $modules = ['entity_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Array of test entities.
    *
diff --git a/core/modules/system/tests/src/Functional/Entity/Update/UpdateApiEntityDefinitionUpdateTest.php b/core/modules/system/tests/src/Functional/Entity/Update/UpdateApiEntityDefinitionUpdateTest.php
index 07352cbc07e9..7efc11b74bfb 100644
--- a/core/modules/system/tests/src/Functional/Entity/Update/UpdateApiEntityDefinitionUpdateTest.php
+++ b/core/modules/system/tests/src/Functional/Entity/Update/UpdateApiEntityDefinitionUpdateTest.php
@@ -22,6 +22,11 @@ class UpdateApiEntityDefinitionUpdateTest extends BrowserTestBase {
    */
   protected static $modules = ['entity_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/File/ConfigTest.php b/core/modules/system/tests/src/Functional/File/ConfigTest.php
index 9d0761fd16d4..f44e8a924a86 100644
--- a/core/modules/system/tests/src/Functional/File/ConfigTest.php
+++ b/core/modules/system/tests/src/Functional/File/ConfigTest.php
@@ -11,6 +11,11 @@
  */
 class ConfigTest extends BrowserTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     $this->drupalLogin($this->drupalCreateUser(['administer site configuration']));
diff --git a/core/modules/system/tests/src/Functional/File/FileSaveHtaccessLoggingTest.php b/core/modules/system/tests/src/Functional/File/FileSaveHtaccessLoggingTest.php
index 7004bc9bcf28..62a0b7a23d5b 100644
--- a/core/modules/system/tests/src/Functional/File/FileSaveHtaccessLoggingTest.php
+++ b/core/modules/system/tests/src/Functional/File/FileSaveHtaccessLoggingTest.php
@@ -14,6 +14,11 @@ class FileSaveHtaccessLoggingTest extends BrowserTestBase {
 
   protected static $modules = ['dblog'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests file_save_htaccess().
    */
diff --git a/core/modules/system/tests/src/Functional/FileTransfer/FileTransferTest.php b/core/modules/system/tests/src/Functional/FileTransfer/FileTransferTest.php
index a15a92a6dbb2..3ec2cbccd87b 100644
--- a/core/modules/system/tests/src/Functional/FileTransfer/FileTransferTest.php
+++ b/core/modules/system/tests/src/Functional/FileTransfer/FileTransferTest.php
@@ -18,6 +18,11 @@ class FileTransferTest extends BrowserTestBase {
   protected $password = 'password';
   protected $port = '42';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     $this->testConnection = TestFileTransfer::factory($this->root, ['hostname' => $this->hostname, 'username' => $this->username, 'password' => $this->password, 'port' => $this->port]);
diff --git a/core/modules/system/tests/src/Functional/Form/AlterTest.php b/core/modules/system/tests/src/Functional/Form/AlterTest.php
index 622a3d1ead10..d1f9667acbdb 100644
--- a/core/modules/system/tests/src/Functional/Form/AlterTest.php
+++ b/core/modules/system/tests/src/Functional/Form/AlterTest.php
@@ -19,6 +19,11 @@ class AlterTest extends BrowserTestBase {
    */
   public static $modules = ['block', 'form_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests execution order of hook_form_alter() and hook_form_FORM_ID_alter().
    */
diff --git a/core/modules/system/tests/src/Functional/Form/ArbitraryRebuildTest.php b/core/modules/system/tests/src/Functional/Form/ArbitraryRebuildTest.php
index 8aa36f08bd24..ce1ebbd7c36d 100644
--- a/core/modules/system/tests/src/Functional/Form/ArbitraryRebuildTest.php
+++ b/core/modules/system/tests/src/Functional/Form/ArbitraryRebuildTest.php
@@ -20,6 +20,11 @@ class ArbitraryRebuildTest extends BrowserTestBase {
    */
   public static $modules = ['text', 'form_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/system/tests/src/Functional/Form/CheckboxTest.php b/core/modules/system/tests/src/Functional/Form/CheckboxTest.php
index a4d9c0904a71..66f7eab1d1ac 100644
--- a/core/modules/system/tests/src/Functional/Form/CheckboxTest.php
+++ b/core/modules/system/tests/src/Functional/Form/CheckboxTest.php
@@ -20,6 +20,11 @@ class CheckboxTest extends BrowserTestBase {
    */
   public static $modules = ['form_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   public function testFormCheckbox() {
     // Ensure that the checked state is determined and rendered correctly for
     // tricky combinations of default and return values.
diff --git a/core/modules/system/tests/src/Functional/Form/ConfirmFormTest.php b/core/modules/system/tests/src/Functional/Form/ConfirmFormTest.php
index ad5a74b69139..421ef4196e07 100644
--- a/core/modules/system/tests/src/Functional/Form/ConfirmFormTest.php
+++ b/core/modules/system/tests/src/Functional/Form/ConfirmFormTest.php
@@ -20,6 +20,11 @@ class ConfirmFormTest extends BrowserTestBase {
    */
   public static $modules = ['form_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   public function testConfirmForm() {
     // Test the building of the form.
     $this->drupalGet('form-test/confirm-form');
diff --git a/core/modules/system/tests/src/Functional/Form/ElementTest.php b/core/modules/system/tests/src/Functional/Form/ElementTest.php
index eb167d428f7b..1ebd39e53517 100644
--- a/core/modules/system/tests/src/Functional/Form/ElementTest.php
+++ b/core/modules/system/tests/src/Functional/Form/ElementTest.php
@@ -19,6 +19,11 @@ class ElementTest extends BrowserTestBase {
    */
   public static $modules = ['form_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Tests placeholder text for elements that support placeholders.
    */
diff --git a/core/modules/system/tests/src/Functional/Form/ElementsAccessTest.php b/core/modules/system/tests/src/Functional/Form/ElementsAccessTest.php
index 1a92893c3929..2167cbb58f6b 100644
--- a/core/modules/system/tests/src/Functional/Form/ElementsAccessTest.php
+++ b/core/modules/system/tests/src/Functional/Form/ElementsAccessTest.php
@@ -18,6 +18,11 @@ class ElementsAccessTest extends BrowserTestBase {
    */
   public static $modules = ['form_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Ensures that child values are still processed when #access = FALSE.
    */
diff --git a/core/modules/system/tests/src/Functional/Form/ElementsContainerTest.php b/core/modules/system/tests/src/Functional/Form/ElementsContainerTest.php
index a7d404b86be5..874cee6dcaa7 100644
--- a/core/modules/system/tests/src/Functional/Form/ElementsContainerTest.php
+++ b/core/modules/system/tests/src/Functional/Form/ElementsContainerTest.php
@@ -18,6 +18,11 @@ class ElementsContainerTest extends BrowserTestBase {
    */
   public static $modules = ['form_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the #optional container property.
    */
diff --git a/core/modules/system/tests/src/Functional/Form/ElementsLabelsTest.php b/core/modules/system/tests/src/Functional/Form/ElementsLabelsTest.php
index 91f3ec4a59d4..0065110ee6cd 100644
--- a/core/modules/system/tests/src/Functional/Form/ElementsLabelsTest.php
+++ b/core/modules/system/tests/src/Functional/Form/ElementsLabelsTest.php
@@ -19,6 +19,11 @@ class ElementsLabelsTest extends BrowserTestBase {
    */
   public static $modules = ['form_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test form elements, labels, title attributes and required marks output
    * correctly and have the correct label option class if needed.
diff --git a/core/modules/system/tests/src/Functional/Form/ElementsTableSelectTest.php b/core/modules/system/tests/src/Functional/Form/ElementsTableSelectTest.php
index f377c0abf60a..90ded5760d22 100644
--- a/core/modules/system/tests/src/Functional/Form/ElementsTableSelectTest.php
+++ b/core/modules/system/tests/src/Functional/Form/ElementsTableSelectTest.php
@@ -19,6 +19,11 @@ class ElementsTableSelectTest extends BrowserTestBase {
    */
   public static $modules = ['form_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test the display of checkboxes when #multiple is TRUE.
    */
diff --git a/core/modules/system/tests/src/Functional/Form/ElementsVerticalTabsTest.php b/core/modules/system/tests/src/Functional/Form/ElementsVerticalTabsTest.php
index 34ca1c9cf811..e90c4dfe3d99 100644
--- a/core/modules/system/tests/src/Functional/Form/ElementsVerticalTabsTest.php
+++ b/core/modules/system/tests/src/Functional/Form/ElementsVerticalTabsTest.php
@@ -20,6 +20,11 @@ class ElementsVerticalTabsTest extends BrowserTestBase {
    */
   public static $modules = ['form_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with permission to access vertical_tab_test_tabs.
    *
diff --git a/core/modules/system/tests/src/Functional/Form/EmailTest.php b/core/modules/system/tests/src/Functional/Form/EmailTest.php
index 2fe6ebe9078f..678f081ebe16 100644
--- a/core/modules/system/tests/src/Functional/Form/EmailTest.php
+++ b/core/modules/system/tests/src/Functional/Form/EmailTest.php
@@ -19,6 +19,11 @@ class EmailTest extends BrowserTestBase {
    */
   public static $modules = ['form_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that #type 'email' fields are properly validated.
    */
diff --git a/core/modules/system/tests/src/Functional/Form/FormObjectTest.php b/core/modules/system/tests/src/Functional/Form/FormObjectTest.php
index e2c00f5d17a8..c2f89735c900 100644
--- a/core/modules/system/tests/src/Functional/Form/FormObjectTest.php
+++ b/core/modules/system/tests/src/Functional/Form/FormObjectTest.php
@@ -18,6 +18,11 @@ class FormObjectTest extends BrowserTestBase {
    */
   public static $modules = ['form_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests using an object as the form callback.
    *
diff --git a/core/modules/system/tests/src/Functional/Form/FormStoragePageCacheTest.php b/core/modules/system/tests/src/Functional/Form/FormStoragePageCacheTest.php
index 474a35b55a97..9f63ead12249 100644
--- a/core/modules/system/tests/src/Functional/Form/FormStoragePageCacheTest.php
+++ b/core/modules/system/tests/src/Functional/Form/FormStoragePageCacheTest.php
@@ -16,6 +16,11 @@ class FormStoragePageCacheTest extends BrowserTestBase {
    */
   public static $modules = ['form_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Form/FormTest.php b/core/modules/system/tests/src/Functional/Form/FormTest.php
index 0551c88322d3..5458f1ef3a96 100644
--- a/core/modules/system/tests/src/Functional/Form/FormTest.php
+++ b/core/modules/system/tests/src/Functional/Form/FormTest.php
@@ -28,6 +28,11 @@ class FormTest extends BrowserTestBase {
    */
   public static $modules = ['filter', 'form_test', 'file', 'datetime'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/system/tests/src/Functional/Form/LanguageSelectElementTest.php b/core/modules/system/tests/src/Functional/Form/LanguageSelectElementTest.php
index 1e77250b60e7..f9f10ca8b8b9 100644
--- a/core/modules/system/tests/src/Functional/Form/LanguageSelectElementTest.php
+++ b/core/modules/system/tests/src/Functional/Form/LanguageSelectElementTest.php
@@ -23,6 +23,11 @@ class LanguageSelectElementTest extends BrowserTestBase {
    */
   public static $modules = ['form_test', 'language'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that the options printed by the language select element are correct.
    */
diff --git a/core/modules/system/tests/src/Functional/Form/ModulesListFormWebTest.php b/core/modules/system/tests/src/Functional/Form/ModulesListFormWebTest.php
index 1e1b2fc579ff..0faac2821a9b 100644
--- a/core/modules/system/tests/src/Functional/Form/ModulesListFormWebTest.php
+++ b/core/modules/system/tests/src/Functional/Form/ModulesListFormWebTest.php
@@ -16,6 +16,11 @@ class ModulesListFormWebTest extends BrowserTestBase {
    */
   public static $modules = ['system_test', 'help'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Form/RebuildTest.php b/core/modules/system/tests/src/Functional/Form/RebuildTest.php
index 3e951e2e802c..6b87f6304225 100644
--- a/core/modules/system/tests/src/Functional/Form/RebuildTest.php
+++ b/core/modules/system/tests/src/Functional/Form/RebuildTest.php
@@ -18,6 +18,11 @@ class RebuildTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'form_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user for testing.
    *
diff --git a/core/modules/system/tests/src/Functional/Form/RedirectTest.php b/core/modules/system/tests/src/Functional/Form/RedirectTest.php
index baaed0d1ded0..e66cc3830873 100644
--- a/core/modules/system/tests/src/Functional/Form/RedirectTest.php
+++ b/core/modules/system/tests/src/Functional/Form/RedirectTest.php
@@ -19,6 +19,11 @@ class RedirectTest extends BrowserTestBase {
    */
   public static $modules = ['form_test', 'block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests form redirection.
    */
diff --git a/core/modules/system/tests/src/Functional/Form/ResponseTest.php b/core/modules/system/tests/src/Functional/Form/ResponseTest.php
index de5d8fd6c7a6..4707a47e501e 100644
--- a/core/modules/system/tests/src/Functional/Form/ResponseTest.php
+++ b/core/modules/system/tests/src/Functional/Form/ResponseTest.php
@@ -19,6 +19,11 @@ class ResponseTest extends BrowserTestBase {
    */
   public static $modules = ['form_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that enforced responses propagate through subscribers and middleware.
    */
diff --git a/core/modules/system/tests/src/Functional/Form/StateValuesCleanAdvancedTest.php b/core/modules/system/tests/src/Functional/Form/StateValuesCleanAdvancedTest.php
index 7341e18994de..56dab576c1ce 100644
--- a/core/modules/system/tests/src/Functional/Form/StateValuesCleanAdvancedTest.php
+++ b/core/modules/system/tests/src/Functional/Form/StateValuesCleanAdvancedTest.php
@@ -25,6 +25,11 @@ class StateValuesCleanAdvancedTest extends BrowserTestBase {
    */
   public static $modules = ['file', 'form_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * An image file path for uploading.
    *
diff --git a/core/modules/system/tests/src/Functional/Form/StateValuesCleanTest.php b/core/modules/system/tests/src/Functional/Form/StateValuesCleanTest.php
index a77b11fd7535..b5bd856de1c9 100644
--- a/core/modules/system/tests/src/Functional/Form/StateValuesCleanTest.php
+++ b/core/modules/system/tests/src/Functional/Form/StateValuesCleanTest.php
@@ -21,6 +21,11 @@ class StateValuesCleanTest extends BrowserTestBase {
    */
   public static $modules = ['form_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests \Drupal\Core\Form\FormState::cleanValues().
    */
diff --git a/core/modules/system/tests/src/Functional/Form/StorageTest.php b/core/modules/system/tests/src/Functional/Form/StorageTest.php
index 95969fde5a2c..32c915e047a6 100644
--- a/core/modules/system/tests/src/Functional/Form/StorageTest.php
+++ b/core/modules/system/tests/src/Functional/Form/StorageTest.php
@@ -27,6 +27,11 @@ class StorageTest extends BrowserTestBase {
    */
   public static $modules = ['form_test', 'dblog'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Form/SystemConfigFormTest.php b/core/modules/system/tests/src/Functional/Form/SystemConfigFormTest.php
index 09ad06ac8c26..e5c5e17ddb1c 100644
--- a/core/modules/system/tests/src/Functional/Form/SystemConfigFormTest.php
+++ b/core/modules/system/tests/src/Functional/Form/SystemConfigFormTest.php
@@ -18,6 +18,11 @@ class SystemConfigFormTest extends BrowserTestBase {
    */
   public static $modules = ['form_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the SystemConfigFormTestBase class.
    */
diff --git a/core/modules/system/tests/src/Functional/Form/UrlTest.php b/core/modules/system/tests/src/Functional/Form/UrlTest.php
index 82d227bbdf95..02197602f781 100644
--- a/core/modules/system/tests/src/Functional/Form/UrlTest.php
+++ b/core/modules/system/tests/src/Functional/Form/UrlTest.php
@@ -21,6 +21,11 @@ class UrlTest extends BrowserTestBase {
 
   protected $profile = 'testing';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that #type 'url' fields are properly validated and trimmed.
    */
diff --git a/core/modules/system/tests/src/Functional/Form/ValidationTest.php b/core/modules/system/tests/src/Functional/Form/ValidationTest.php
index ccb15ade16dd..cadf427581eb 100644
--- a/core/modules/system/tests/src/Functional/Form/ValidationTest.php
+++ b/core/modules/system/tests/src/Functional/Form/ValidationTest.php
@@ -20,6 +20,11 @@ class ValidationTest extends BrowserTestBase {
    */
   public static $modules = ['form_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests #element_validate and #validate.
    */
diff --git a/core/modules/system/tests/src/Functional/Hal/ActionHalJsonAnonTest.php b/core/modules/system/tests/src/Functional/Hal/ActionHalJsonAnonTest.php
index eb19bac6f129..6c0ad70cbcd8 100644
--- a/core/modules/system/tests/src/Functional/Hal/ActionHalJsonAnonTest.php
+++ b/core/modules/system/tests/src/Functional/Hal/ActionHalJsonAnonTest.php
@@ -17,6 +17,11 @@ class ActionHalJsonAnonTest extends ActionResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Hal/ActionHalJsonBasicAuthTest.php b/core/modules/system/tests/src/Functional/Hal/ActionHalJsonBasicAuthTest.php
index 7441f6ab4bcd..13daf5b04121 100644
--- a/core/modules/system/tests/src/Functional/Hal/ActionHalJsonBasicAuthTest.php
+++ b/core/modules/system/tests/src/Functional/Hal/ActionHalJsonBasicAuthTest.php
@@ -17,6 +17,11 @@ class ActionHalJsonBasicAuthTest extends ActionResourceTestBase {
    */
   public static $modules = ['hal', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Hal/ActionHalJsonCookieTest.php b/core/modules/system/tests/src/Functional/Hal/ActionHalJsonCookieTest.php
index f013032e8516..2a9c6178b950 100644
--- a/core/modules/system/tests/src/Functional/Hal/ActionHalJsonCookieTest.php
+++ b/core/modules/system/tests/src/Functional/Hal/ActionHalJsonCookieTest.php
@@ -17,6 +17,11 @@ class ActionHalJsonCookieTest extends ActionResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Hal/MenuHalJsonAnonTest.php b/core/modules/system/tests/src/Functional/Hal/MenuHalJsonAnonTest.php
index 0200624b162c..04dd30e6ce2d 100644
--- a/core/modules/system/tests/src/Functional/Hal/MenuHalJsonAnonTest.php
+++ b/core/modules/system/tests/src/Functional/Hal/MenuHalJsonAnonTest.php
@@ -17,6 +17,11 @@ class MenuHalJsonAnonTest extends MenuResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Hal/MenuHalJsonBasicAuthTest.php b/core/modules/system/tests/src/Functional/Hal/MenuHalJsonBasicAuthTest.php
index cce118b1186b..3aaa10a0c91c 100644
--- a/core/modules/system/tests/src/Functional/Hal/MenuHalJsonBasicAuthTest.php
+++ b/core/modules/system/tests/src/Functional/Hal/MenuHalJsonBasicAuthTest.php
@@ -17,6 +17,11 @@ class MenuHalJsonBasicAuthTest extends MenuResourceTestBase {
    */
   public static $modules = ['hal', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Hal/MenuHalJsonCookieTest.php b/core/modules/system/tests/src/Functional/Hal/MenuHalJsonCookieTest.php
index 9f7346f2592e..0d706f4585ab 100644
--- a/core/modules/system/tests/src/Functional/Hal/MenuHalJsonCookieTest.php
+++ b/core/modules/system/tests/src/Functional/Hal/MenuHalJsonCookieTest.php
@@ -17,6 +17,11 @@ class MenuHalJsonCookieTest extends MenuResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Lock/LockFunctionalTest.php b/core/modules/system/tests/src/Functional/Lock/LockFunctionalTest.php
index 0b13f18d6266..766e81f7b7ac 100644
--- a/core/modules/system/tests/src/Functional/Lock/LockFunctionalTest.php
+++ b/core/modules/system/tests/src/Functional/Lock/LockFunctionalTest.php
@@ -18,6 +18,11 @@ class LockFunctionalTest extends BrowserTestBase {
    */
   public static $modules = ['system_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Confirms that we can acquire and release locks in two parallel requests.
    */
diff --git a/core/modules/system/tests/src/Functional/Mail/HtmlToTextTest.php b/core/modules/system/tests/src/Functional/Mail/HtmlToTextTest.php
index 97092232d76e..72b1fb2dd5d9 100644
--- a/core/modules/system/tests/src/Functional/Mail/HtmlToTextTest.php
+++ b/core/modules/system/tests/src/Functional/Mail/HtmlToTextTest.php
@@ -14,6 +14,11 @@
  */
 class HtmlToTextTest extends BrowserTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Converts a string to its PHP source equivalent for display in test messages.
    *
diff --git a/core/modules/system/tests/src/Functional/Menu/BreadcrumbFrontCacheContextsTest.php b/core/modules/system/tests/src/Functional/Menu/BreadcrumbFrontCacheContextsTest.php
index 902720946723..2ede1c967398 100644
--- a/core/modules/system/tests/src/Functional/Menu/BreadcrumbFrontCacheContextsTest.php
+++ b/core/modules/system/tests/src/Functional/Menu/BreadcrumbFrontCacheContextsTest.php
@@ -25,6 +25,11 @@ class BreadcrumbFrontCacheContextsTest extends BrowserTestBase {
     'user',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * A test node with path alias.
    *
diff --git a/core/modules/system/tests/src/Functional/Menu/LocalActionTest.php b/core/modules/system/tests/src/Functional/Menu/LocalActionTest.php
index f7b9aafae40c..67875aa8d1c0 100644
--- a/core/modules/system/tests/src/Functional/Menu/LocalActionTest.php
+++ b/core/modules/system/tests/src/Functional/Menu/LocalActionTest.php
@@ -20,6 +20,11 @@ class LocalActionTest extends BrowserTestBase {
    */
   public static $modules = ['block', 'menu_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Menu/LocalTasksTest.php b/core/modules/system/tests/src/Functional/Menu/LocalTasksTest.php
index 0afc71162423..59e9becdd5f5 100644
--- a/core/modules/system/tests/src/Functional/Menu/LocalTasksTest.php
+++ b/core/modules/system/tests/src/Functional/Menu/LocalTasksTest.php
@@ -21,6 +21,11 @@ class LocalTasksTest extends BrowserTestBase {
    */
   public static $modules = ['block', 'menu_test', 'entity_test', 'node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * The local tasks block under testing.
    *
diff --git a/core/modules/system/tests/src/Functional/Menu/MenuAccessTest.php b/core/modules/system/tests/src/Functional/Menu/MenuAccessTest.php
index 7d3c0a4b3ddd..8c0b7ca49863 100644
--- a/core/modules/system/tests/src/Functional/Menu/MenuAccessTest.php
+++ b/core/modules/system/tests/src/Functional/Menu/MenuAccessTest.php
@@ -19,6 +19,11 @@ class MenuAccessTest extends BrowserTestBase {
    */
   public static $modules = ['block', 'menu_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Menu/MenuLinkSecurityTest.php b/core/modules/system/tests/src/Functional/Menu/MenuLinkSecurityTest.php
index c58bf8e504dc..d9433be31fa4 100644
--- a/core/modules/system/tests/src/Functional/Menu/MenuLinkSecurityTest.php
+++ b/core/modules/system/tests/src/Functional/Menu/MenuLinkSecurityTest.php
@@ -17,6 +17,11 @@ class MenuLinkSecurityTest extends BrowserTestBase {
    */
   public static $modules = ['menu_link_content', 'block', 'menu_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Ensures that a menu link does not cause an XSS issue.
    */
diff --git a/core/modules/system/tests/src/Functional/Menu/MenuRouterTest.php b/core/modules/system/tests/src/Functional/Menu/MenuRouterTest.php
index 882d92365af5..f13707fff08c 100644
--- a/core/modules/system/tests/src/Functional/Menu/MenuRouterTest.php
+++ b/core/modules/system/tests/src/Functional/Menu/MenuRouterTest.php
@@ -20,18 +20,16 @@ class MenuRouterTest extends BrowserTestBase {
   public static $modules = ['block', 'menu_test', 'test_page_test'];
 
   /**
-   * Name of the administrative theme to use for tests.
-   *
-   * @var string
+   * {@inheritdoc}
    */
-  protected $adminTheme;
+  protected $defaultTheme = 'stark';
 
   /**
-   * Name of the default theme to use for tests.
+   * Name of the administrative theme to use for tests.
    *
    * @var string
    */
-  protected $defaultTheme;
+  protected $adminTheme;
 
   protected function setUp() {
     // Enable dummy module that implements hook_menu.
diff --git a/core/modules/system/tests/src/Functional/Module/ClassLoaderTest.php b/core/modules/system/tests/src/Functional/Module/ClassLoaderTest.php
index 335a03a329b0..db82fe25f843 100644
--- a/core/modules/system/tests/src/Functional/Module/ClassLoaderTest.php
+++ b/core/modules/system/tests/src/Functional/Module/ClassLoaderTest.php
@@ -23,6 +23,11 @@ class ClassLoaderTest extends BrowserTestBase {
    */
   protected $apcuEnsureUniquePrefix = TRUE;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that module-provided classes can be loaded when a module is enabled.
    *
diff --git a/core/modules/system/tests/src/Functional/Module/DependencyTest.php b/core/modules/system/tests/src/Functional/Module/DependencyTest.php
index adb8da9a56bd..7d749f6020f1 100644
--- a/core/modules/system/tests/src/Functional/Module/DependencyTest.php
+++ b/core/modules/system/tests/src/Functional/Module/DependencyTest.php
@@ -11,6 +11,11 @@
  */
 class DependencyTest extends ModuleTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Checks functionality of project namespaces for dependencies.
    */
diff --git a/core/modules/system/tests/src/Functional/Module/ExperimentalModuleTest.php b/core/modules/system/tests/src/Functional/Module/ExperimentalModuleTest.php
index 177fc5ba1de8..eba632f0f9c6 100644
--- a/core/modules/system/tests/src/Functional/Module/ExperimentalModuleTest.php
+++ b/core/modules/system/tests/src/Functional/Module/ExperimentalModuleTest.php
@@ -19,6 +19,11 @@ class ExperimentalModuleTest extends BrowserTestBase {
    */
   protected $adminUser;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Module/HookRequirementsTest.php b/core/modules/system/tests/src/Functional/Module/HookRequirementsTest.php
index 2ada3a2854d9..317634b4d292 100644
--- a/core/modules/system/tests/src/Functional/Module/HookRequirementsTest.php
+++ b/core/modules/system/tests/src/Functional/Module/HookRequirementsTest.php
@@ -9,6 +9,11 @@
  */
 class HookRequirementsTest extends ModuleTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Assert that a module cannot be installed if it fails hook_requirements().
    */
diff --git a/core/modules/system/tests/src/Functional/Module/InstallTest.php b/core/modules/system/tests/src/Functional/Module/InstallTest.php
index 43b66782f3a9..08acec5b4cc2 100644
--- a/core/modules/system/tests/src/Functional/Module/InstallTest.php
+++ b/core/modules/system/tests/src/Functional/Module/InstallTest.php
@@ -21,6 +21,11 @@ class InstallTest extends BrowserTestBase {
    */
   public static $modules = ['module_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Verify that drupal_get_schema() can be used during module installation.
    */
diff --git a/core/modules/system/tests/src/Functional/Module/InstallUninstallTest.php b/core/modules/system/tests/src/Functional/Module/InstallUninstallTest.php
index fd84c4db7ec1..31fb1b793117 100644
--- a/core/modules/system/tests/src/Functional/Module/InstallUninstallTest.php
+++ b/core/modules/system/tests/src/Functional/Module/InstallUninstallTest.php
@@ -14,6 +14,11 @@
  */
 class InstallUninstallTest extends ModuleTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Module/PrepareUninstallTest.php b/core/modules/system/tests/src/Functional/Module/PrepareUninstallTest.php
index 56e888d5c5f4..fdabecdbec88 100644
--- a/core/modules/system/tests/src/Functional/Module/PrepareUninstallTest.php
+++ b/core/modules/system/tests/src/Functional/Module/PrepareUninstallTest.php
@@ -14,6 +14,11 @@ class PrepareUninstallTest extends BrowserTestBase {
 
   use TaxonomyTestTrait;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * An array of node objects.
    *
diff --git a/core/modules/system/tests/src/Functional/Module/UninstallTest.php b/core/modules/system/tests/src/Functional/Module/UninstallTest.php
index d061646f7e9a..c4202a4cdaf2 100644
--- a/core/modules/system/tests/src/Functional/Module/UninstallTest.php
+++ b/core/modules/system/tests/src/Functional/Module/UninstallTest.php
@@ -23,6 +23,11 @@ class UninstallTest extends BrowserTestBase {
    */
   public static $modules = ['module_test', 'user', 'views', 'node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the hook_modules_uninstalled() of the user module.
    */
diff --git a/core/modules/system/tests/src/Functional/Module/VersionTest.php b/core/modules/system/tests/src/Functional/Module/VersionTest.php
index 7b325fef8f03..2935edf2ac62 100644
--- a/core/modules/system/tests/src/Functional/Module/VersionTest.php
+++ b/core/modules/system/tests/src/Functional/Module/VersionTest.php
@@ -9,6 +9,11 @@
  */
 class VersionTest extends ModuleTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test version dependencies.
    */
diff --git a/core/modules/system/tests/src/Functional/Page/DefaultMetatagsTest.php b/core/modules/system/tests/src/Functional/Page/DefaultMetatagsTest.php
index d020368c525b..2493a38306df 100644
--- a/core/modules/system/tests/src/Functional/Page/DefaultMetatagsTest.php
+++ b/core/modules/system/tests/src/Functional/Page/DefaultMetatagsTest.php
@@ -11,6 +11,11 @@
  */
 class DefaultMetatagsTest extends BrowserTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests meta tags.
    */
diff --git a/core/modules/system/tests/src/Functional/Pager/PagerTest.php b/core/modules/system/tests/src/Functional/Pager/PagerTest.php
index 7edbaa07757f..7d30b145078e 100644
--- a/core/modules/system/tests/src/Functional/Pager/PagerTest.php
+++ b/core/modules/system/tests/src/Functional/Pager/PagerTest.php
@@ -22,6 +22,11 @@ class PagerTest extends BrowserTestBase {
    */
   public static $modules = ['dblog', 'image', 'pager_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with permission to access site reports.
    *
diff --git a/core/modules/system/tests/src/Functional/ParamConverter/UpcastingTest.php b/core/modules/system/tests/src/Functional/ParamConverter/UpcastingTest.php
index faafe84600ac..a0f3caff88ff 100644
--- a/core/modules/system/tests/src/Functional/ParamConverter/UpcastingTest.php
+++ b/core/modules/system/tests/src/Functional/ParamConverter/UpcastingTest.php
@@ -14,6 +14,11 @@ class UpcastingTest extends BrowserTestBase {
 
   public static $modules = ['paramconverter_test', 'node', 'language'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Confirms that all parameters are converted as expected.
    *
diff --git a/core/modules/system/tests/src/Functional/Render/AjaxPageStateTest.php b/core/modules/system/tests/src/Functional/Render/AjaxPageStateTest.php
index 415a42881abb..20c68695b857 100644
--- a/core/modules/system/tests/src/Functional/Render/AjaxPageStateTest.php
+++ b/core/modules/system/tests/src/Functional/Render/AjaxPageStateTest.php
@@ -18,6 +18,11 @@ class AjaxPageStateTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * User account with all available permissions
    *
diff --git a/core/modules/system/tests/src/Functional/Render/DisplayVariantTest.php b/core/modules/system/tests/src/Functional/Render/DisplayVariantTest.php
index 2f5415ba7c44..c10866acd16d 100644
--- a/core/modules/system/tests/src/Functional/Render/DisplayVariantTest.php
+++ b/core/modules/system/tests/src/Functional/Render/DisplayVariantTest.php
@@ -18,6 +18,11 @@ class DisplayVariantTest extends BrowserTestBase {
    */
   public static $modules = ['display_variant_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests selecting the variant and passing configuration.
    */
diff --git a/core/modules/system/tests/src/Functional/Render/HtmlResponseAttachmentsTest.php b/core/modules/system/tests/src/Functional/Render/HtmlResponseAttachmentsTest.php
index 2bd6d289c6f8..382a3442e79a 100644
--- a/core/modules/system/tests/src/Functional/Render/HtmlResponseAttachmentsTest.php
+++ b/core/modules/system/tests/src/Functional/Render/HtmlResponseAttachmentsTest.php
@@ -18,6 +18,11 @@ class HtmlResponseAttachmentsTest extends BrowserTestBase {
    */
   public static $modules = ['render_attached_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test rendering of ['#attached'].
    */
diff --git a/core/modules/system/tests/src/Functional/Render/PlaceholderMessageTest.php b/core/modules/system/tests/src/Functional/Render/PlaceholderMessageTest.php
index 185ca4985a0c..97ca6d22d2ac 100644
--- a/core/modules/system/tests/src/Functional/Render/PlaceholderMessageTest.php
+++ b/core/modules/system/tests/src/Functional/Render/PlaceholderMessageTest.php
@@ -19,6 +19,11 @@ class PlaceholderMessageTest extends BrowserTestBase {
    */
   public static $modules = ['render_placeholder_message_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test rendering of message placeholder.
    */
diff --git a/core/modules/system/tests/src/Functional/Render/RenderArrayNonHtmlSubscriberTest.php b/core/modules/system/tests/src/Functional/Render/RenderArrayNonHtmlSubscriberTest.php
index 08380dec024e..4f02d1a7c911 100644
--- a/core/modules/system/tests/src/Functional/Render/RenderArrayNonHtmlSubscriberTest.php
+++ b/core/modules/system/tests/src/Functional/Render/RenderArrayNonHtmlSubscriberTest.php
@@ -19,6 +19,11 @@ class RenderArrayNonHtmlSubscriberTest extends BrowserTestBase {
    */
   public static $modules = ['render_array_non_html_subscriber_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests handling of responses by events subscriber.
    */
diff --git a/core/modules/system/tests/src/Functional/Render/UrlBubbleableMetadataBubblingTest.php b/core/modules/system/tests/src/Functional/Render/UrlBubbleableMetadataBubblingTest.php
index 37d20ce3b83a..4c25fceeb836 100644
--- a/core/modules/system/tests/src/Functional/Render/UrlBubbleableMetadataBubblingTest.php
+++ b/core/modules/system/tests/src/Functional/Render/UrlBubbleableMetadataBubblingTest.php
@@ -22,6 +22,11 @@ class UrlBubbleableMetadataBubblingTest extends BrowserTestBase {
    */
   public static $modules = ['cache_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Rest/ActionJsonAnonTest.php b/core/modules/system/tests/src/Functional/Rest/ActionJsonAnonTest.php
index 07a7a5b3dd58..a3da1f60399d 100644
--- a/core/modules/system/tests/src/Functional/Rest/ActionJsonAnonTest.php
+++ b/core/modules/system/tests/src/Functional/Rest/ActionJsonAnonTest.php
@@ -21,4 +21,9 @@ class ActionJsonAnonTest extends ActionResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/system/tests/src/Functional/Rest/ActionJsonBasicAuthTest.php b/core/modules/system/tests/src/Functional/Rest/ActionJsonBasicAuthTest.php
index fdc516b9e4ab..98c1d9a2a857 100644
--- a/core/modules/system/tests/src/Functional/Rest/ActionJsonBasicAuthTest.php
+++ b/core/modules/system/tests/src/Functional/Rest/ActionJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class ActionJsonBasicAuthTest extends ActionResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Rest/ActionJsonCookieTest.php b/core/modules/system/tests/src/Functional/Rest/ActionJsonCookieTest.php
index 0766f03f080c..82194e8670a0 100644
--- a/core/modules/system/tests/src/Functional/Rest/ActionJsonCookieTest.php
+++ b/core/modules/system/tests/src/Functional/Rest/ActionJsonCookieTest.php
@@ -26,4 +26,9 @@ class ActionJsonCookieTest extends ActionResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/system/tests/src/Functional/Rest/ActionXmlAnonTest.php b/core/modules/system/tests/src/Functional/Rest/ActionXmlAnonTest.php
index e45af980ea12..db0e28ab0b5e 100644
--- a/core/modules/system/tests/src/Functional/Rest/ActionXmlAnonTest.php
+++ b/core/modules/system/tests/src/Functional/Rest/ActionXmlAnonTest.php
@@ -23,4 +23,9 @@ class ActionXmlAnonTest extends ActionResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/system/tests/src/Functional/Rest/ActionXmlBasicAuthTest.php b/core/modules/system/tests/src/Functional/Rest/ActionXmlBasicAuthTest.php
index f11459bc6d0e..0e90dbea3121 100644
--- a/core/modules/system/tests/src/Functional/Rest/ActionXmlBasicAuthTest.php
+++ b/core/modules/system/tests/src/Functional/Rest/ActionXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class ActionXmlBasicAuthTest extends ActionResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Rest/ActionXmlCookieTest.php b/core/modules/system/tests/src/Functional/Rest/ActionXmlCookieTest.php
index dbee6fa1af3b..71c703c27c1b 100644
--- a/core/modules/system/tests/src/Functional/Rest/ActionXmlCookieTest.php
+++ b/core/modules/system/tests/src/Functional/Rest/ActionXmlCookieTest.php
@@ -28,4 +28,9 @@ class ActionXmlCookieTest extends ActionResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/system/tests/src/Functional/Rest/MenuJsonAnonTest.php b/core/modules/system/tests/src/Functional/Rest/MenuJsonAnonTest.php
index 468deb5178e0..fbd61d7e83e7 100644
--- a/core/modules/system/tests/src/Functional/Rest/MenuJsonAnonTest.php
+++ b/core/modules/system/tests/src/Functional/Rest/MenuJsonAnonTest.php
@@ -21,4 +21,9 @@ class MenuJsonAnonTest extends MenuResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/system/tests/src/Functional/Rest/MenuJsonBasicAuthTest.php b/core/modules/system/tests/src/Functional/Rest/MenuJsonBasicAuthTest.php
index 1d35d421619d..5b9fe9e3bc06 100644
--- a/core/modules/system/tests/src/Functional/Rest/MenuJsonBasicAuthTest.php
+++ b/core/modules/system/tests/src/Functional/Rest/MenuJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class MenuJsonBasicAuthTest extends MenuResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Rest/MenuJsonCookieTest.php b/core/modules/system/tests/src/Functional/Rest/MenuJsonCookieTest.php
index d923875e1531..85c880028e2c 100644
--- a/core/modules/system/tests/src/Functional/Rest/MenuJsonCookieTest.php
+++ b/core/modules/system/tests/src/Functional/Rest/MenuJsonCookieTest.php
@@ -26,4 +26,9 @@ class MenuJsonCookieTest extends MenuResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/system/tests/src/Functional/Rest/MenuXmlAnonTest.php b/core/modules/system/tests/src/Functional/Rest/MenuXmlAnonTest.php
index e1c23b5f70f6..cf9d2101f734 100644
--- a/core/modules/system/tests/src/Functional/Rest/MenuXmlAnonTest.php
+++ b/core/modules/system/tests/src/Functional/Rest/MenuXmlAnonTest.php
@@ -23,4 +23,9 @@ class MenuXmlAnonTest extends MenuResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/system/tests/src/Functional/Rest/MenuXmlBasicAuthTest.php b/core/modules/system/tests/src/Functional/Rest/MenuXmlBasicAuthTest.php
index 091043004285..9f786dd4de4b 100644
--- a/core/modules/system/tests/src/Functional/Rest/MenuXmlBasicAuthTest.php
+++ b/core/modules/system/tests/src/Functional/Rest/MenuXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class MenuXmlBasicAuthTest extends MenuResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Rest/MenuXmlCookieTest.php b/core/modules/system/tests/src/Functional/Rest/MenuXmlCookieTest.php
index a229b6a3b278..45f6a79699ee 100644
--- a/core/modules/system/tests/src/Functional/Rest/MenuXmlCookieTest.php
+++ b/core/modules/system/tests/src/Functional/Rest/MenuXmlCookieTest.php
@@ -28,4 +28,9 @@ class MenuXmlCookieTest extends MenuResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/system/tests/src/Functional/Routing/DestinationTest.php b/core/modules/system/tests/src/Functional/Routing/DestinationTest.php
index 109d8000074d..98ec29b47312 100644
--- a/core/modules/system/tests/src/Functional/Routing/DestinationTest.php
+++ b/core/modules/system/tests/src/Functional/Routing/DestinationTest.php
@@ -22,6 +22,11 @@ class DestinationTest extends BrowserTestBase {
    */
   public static $modules = ['system_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that $_GET/$_REQUEST['destination'] only contain internal URLs.
    */
diff --git a/core/modules/system/tests/src/Functional/Routing/RouterPermissionTest.php b/core/modules/system/tests/src/Functional/Routing/RouterPermissionTest.php
index 62a511f2e438..1985725ef356 100644
--- a/core/modules/system/tests/src/Functional/Routing/RouterPermissionTest.php
+++ b/core/modules/system/tests/src/Functional/Routing/RouterPermissionTest.php
@@ -18,6 +18,11 @@ class RouterPermissionTest extends BrowserTestBase {
    */
   public static $modules = ['router_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests permission requirements on routes.
    */
diff --git a/core/modules/system/tests/src/Functional/Routing/RouterTest.php b/core/modules/system/tests/src/Functional/Routing/RouterTest.php
index 47361411b981..974afee8651c 100644
--- a/core/modules/system/tests/src/Functional/Routing/RouterTest.php
+++ b/core/modules/system/tests/src/Functional/Routing/RouterTest.php
@@ -23,6 +23,11 @@ class RouterTest extends BrowserTestBase {
    */
   public static $modules = ['router_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Confirms that our FinishResponseSubscriber logic works properly.
    */
diff --git a/core/modules/system/tests/src/Functional/ServiceProvider/ServiceProviderWebTest.php b/core/modules/system/tests/src/Functional/ServiceProvider/ServiceProviderWebTest.php
index 5e86164f6e6d..773c1795ecdf 100644
--- a/core/modules/system/tests/src/Functional/ServiceProvider/ServiceProviderWebTest.php
+++ b/core/modules/system/tests/src/Functional/ServiceProvider/ServiceProviderWebTest.php
@@ -18,6 +18,11 @@ class ServiceProviderWebTest extends BrowserTestBase {
    */
   public static $modules = ['file', 'service_provider_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that module service providers get registered to the DIC.
    *
diff --git a/core/modules/system/tests/src/Functional/Session/SessionAuthenticationTest.php b/core/modules/system/tests/src/Functional/Session/SessionAuthenticationTest.php
index 7825877686f0..702486d99e40 100644
--- a/core/modules/system/tests/src/Functional/Session/SessionAuthenticationTest.php
+++ b/core/modules/system/tests/src/Functional/Session/SessionAuthenticationTest.php
@@ -27,6 +27,11 @@ class SessionAuthenticationTest extends BrowserTestBase {
    */
   public static $modules = ['basic_auth', 'session_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Session/SessionHttpsTest.php b/core/modules/system/tests/src/Functional/Session/SessionHttpsTest.php
index 13292b4d6151..dbdbe664cea5 100644
--- a/core/modules/system/tests/src/Functional/Session/SessionHttpsTest.php
+++ b/core/modules/system/tests/src/Functional/Session/SessionHttpsTest.php
@@ -38,6 +38,11 @@ class SessionHttpsTest extends BrowserTestBase {
    */
   public static $modules = ['session_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Session/SessionTest.php b/core/modules/system/tests/src/Functional/Session/SessionTest.php
index 0822fe435c46..7141ba45394d 100644
--- a/core/modules/system/tests/src/Functional/Session/SessionTest.php
+++ b/core/modules/system/tests/src/Functional/Session/SessionTest.php
@@ -20,6 +20,11 @@ class SessionTest extends BrowserTestBase {
    */
   public static $modules = ['session_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected $dumpHeaders = TRUE;
 
   /**
diff --git a/core/modules/system/tests/src/Functional/Session/StackSessionHandlerIntegrationTest.php b/core/modules/system/tests/src/Functional/Session/StackSessionHandlerIntegrationTest.php
index d65ba4216044..9b71436175cf 100644
--- a/core/modules/system/tests/src/Functional/Session/StackSessionHandlerIntegrationTest.php
+++ b/core/modules/system/tests/src/Functional/Session/StackSessionHandlerIntegrationTest.php
@@ -17,6 +17,11 @@ class StackSessionHandlerIntegrationTest extends BrowserTestBase {
    */
   protected static $modules = ['session_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests a request.
    */
diff --git a/core/modules/system/tests/src/Functional/System/AccessDeniedTest.php b/core/modules/system/tests/src/Functional/System/AccessDeniedTest.php
index c0749b490caa..4c4b0cb1c5c4 100644
--- a/core/modules/system/tests/src/Functional/System/AccessDeniedTest.php
+++ b/core/modules/system/tests/src/Functional/System/AccessDeniedTest.php
@@ -23,6 +23,11 @@ class AccessDeniedTest extends BrowserTestBase {
    */
   public static $modules = ['block', 'node', 'system_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected $adminUser;
 
   protected function setUp() {
diff --git a/core/modules/system/tests/src/Functional/System/AdminMetaTagTest.php b/core/modules/system/tests/src/Functional/System/AdminMetaTagTest.php
index 6fcc4b848d18..d17e537b679c 100644
--- a/core/modules/system/tests/src/Functional/System/AdminMetaTagTest.php
+++ b/core/modules/system/tests/src/Functional/System/AdminMetaTagTest.php
@@ -11,6 +11,11 @@
  */
 class AdminMetaTagTest extends BrowserTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Verify that the meta tag HTML is generated correctly.
    */
diff --git a/core/modules/system/tests/src/Functional/System/AdminTest.php b/core/modules/system/tests/src/Functional/System/AdminTest.php
index 7a0b2a3ae6c1..a80651951245 100644
--- a/core/modules/system/tests/src/Functional/System/AdminTest.php
+++ b/core/modules/system/tests/src/Functional/System/AdminTest.php
@@ -33,6 +33,11 @@ class AdminTest extends BrowserTestBase {
    */
   public static $modules = ['locale'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     // testAdminPages() requires Locale module.
     parent::setUp();
diff --git a/core/modules/system/tests/src/Functional/System/CronRunTest.php b/core/modules/system/tests/src/Functional/System/CronRunTest.php
index 12b86c83e7ed..eecd9db7f705 100644
--- a/core/modules/system/tests/src/Functional/System/CronRunTest.php
+++ b/core/modules/system/tests/src/Functional/System/CronRunTest.php
@@ -21,6 +21,11 @@ class CronRunTest extends BrowserTestBase {
    */
   public static $modules = ['common_test', 'common_test_cron_helper', 'automated_cron'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test cron runs.
    */
diff --git a/core/modules/system/tests/src/Functional/System/DateFormatsLockedTest.php b/core/modules/system/tests/src/Functional/System/DateFormatsLockedTest.php
index faac2b76277f..d09d8d134803 100644
--- a/core/modules/system/tests/src/Functional/System/DateFormatsLockedTest.php
+++ b/core/modules/system/tests/src/Functional/System/DateFormatsLockedTest.php
@@ -11,6 +11,11 @@
  */
 class DateFormatsLockedTest extends BrowserTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests attempts at listing, editing, and deleting locked date formats.
    */
diff --git a/core/modules/system/tests/src/Functional/System/DateFormatsMachineNameTest.php b/core/modules/system/tests/src/Functional/System/DateFormatsMachineNameTest.php
index fd88bdc77fd2..606a287a20bc 100644
--- a/core/modules/system/tests/src/Functional/System/DateFormatsMachineNameTest.php
+++ b/core/modules/system/tests/src/Functional/System/DateFormatsMachineNameTest.php
@@ -11,6 +11,11 @@
  */
 class DateFormatsMachineNameTest extends BrowserTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/System/DateTimeTest.php b/core/modules/system/tests/src/Functional/System/DateTimeTest.php
index 0a365a7a7dab..0ecebb433a65 100644
--- a/core/modules/system/tests/src/Functional/System/DateTimeTest.php
+++ b/core/modules/system/tests/src/Functional/System/DateTimeTest.php
@@ -21,6 +21,11 @@ class DateTimeTest extends BrowserTestBase {
    */
   public static $modules = ['block', 'node', 'language', 'field', 'field_ui', 'datetime', 'options'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/system/tests/src/Functional/System/DefaultMobileMetaTagsTest.php b/core/modules/system/tests/src/Functional/System/DefaultMobileMetaTagsTest.php
index 922839f99539..a8f54bad60be 100644
--- a/core/modules/system/tests/src/Functional/System/DefaultMobileMetaTagsTest.php
+++ b/core/modules/system/tests/src/Functional/System/DefaultMobileMetaTagsTest.php
@@ -19,6 +19,11 @@ class DefaultMobileMetaTagsTest extends BrowserTestBase {
    */
   protected $defaultMetaTags;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     $this->defaultMetaTags = [
diff --git a/core/modules/system/tests/src/Functional/System/ErrorHandlerTest.php b/core/modules/system/tests/src/Functional/System/ErrorHandlerTest.php
index 729053744148..5b4a7d17486a 100644
--- a/core/modules/system/tests/src/Functional/System/ErrorHandlerTest.php
+++ b/core/modules/system/tests/src/Functional/System/ErrorHandlerTest.php
@@ -19,6 +19,11 @@ class ErrorHandlerTest extends BrowserTestBase {
    */
   public static $modules = ['error_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test the error handler.
    */
diff --git a/core/modules/system/tests/src/Functional/System/FrontPageTest.php b/core/modules/system/tests/src/Functional/System/FrontPageTest.php
index 7f9fc8c1f071..98bab99adee9 100644
--- a/core/modules/system/tests/src/Functional/System/FrontPageTest.php
+++ b/core/modules/system/tests/src/Functional/System/FrontPageTest.php
@@ -19,6 +19,11 @@ class FrontPageTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'system_test', 'views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The path to a node that is created for testing.
    *
diff --git a/core/modules/system/tests/src/Functional/System/HtaccessTest.php b/core/modules/system/tests/src/Functional/System/HtaccessTest.php
index 7d8ea086ed68..037a92a00fe3 100644
--- a/core/modules/system/tests/src/Functional/System/HtaccessTest.php
+++ b/core/modules/system/tests/src/Functional/System/HtaccessTest.php
@@ -18,6 +18,11 @@ class HtaccessTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'path'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Get an array of file paths for access testing.
    *
diff --git a/core/modules/system/tests/src/Functional/System/IndexPhpTest.php b/core/modules/system/tests/src/Functional/System/IndexPhpTest.php
index 4675fed0faa0..4146d0c655cf 100644
--- a/core/modules/system/tests/src/Functional/System/IndexPhpTest.php
+++ b/core/modules/system/tests/src/Functional/System/IndexPhpTest.php
@@ -11,6 +11,11 @@
  */
 class IndexPhpTest extends BrowserTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
   }
diff --git a/core/modules/system/tests/src/Functional/System/MainContentFallbackTest.php b/core/modules/system/tests/src/Functional/System/MainContentFallbackTest.php
index 931b84ce2422..acbb60aa8bda 100644
--- a/core/modules/system/tests/src/Functional/System/MainContentFallbackTest.php
+++ b/core/modules/system/tests/src/Functional/System/MainContentFallbackTest.php
@@ -18,6 +18,11 @@ class MainContentFallbackTest extends BrowserTestBase {
    */
   public static $modules = ['block', 'system_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected $adminUser;
   protected $webUser;
 
diff --git a/core/modules/system/tests/src/Functional/System/PageNotFoundTest.php b/core/modules/system/tests/src/Functional/System/PageNotFoundTest.php
index 060f53aa1966..45522da9bd39 100644
--- a/core/modules/system/tests/src/Functional/System/PageNotFoundTest.php
+++ b/core/modules/system/tests/src/Functional/System/PageNotFoundTest.php
@@ -23,6 +23,11 @@ class PageNotFoundTest extends BrowserTestBase {
    */
   public static $modules = ['system_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected $adminUser;
 
   protected function setUp() {
diff --git a/core/modules/system/tests/src/Functional/System/PageTitleTest.php b/core/modules/system/tests/src/Functional/System/PageTitleTest.php
index 8073827fb271..bc2ed2018824 100644
--- a/core/modules/system/tests/src/Functional/System/PageTitleTest.php
+++ b/core/modules/system/tests/src/Functional/System/PageTitleTest.php
@@ -21,6 +21,11 @@ class PageTitleTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'test_page_test', 'form_test', 'block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   protected $contentUser;
   protected $savedTitle;
 
diff --git a/core/modules/system/tests/src/Functional/System/ResponseGeneratorTest.php b/core/modules/system/tests/src/Functional/System/ResponseGeneratorTest.php
index d0f2ab539a43..5c8f547c4d57 100644
--- a/core/modules/system/tests/src/Functional/System/ResponseGeneratorTest.php
+++ b/core/modules/system/tests/src/Functional/System/ResponseGeneratorTest.php
@@ -19,6 +19,11 @@ class ResponseGeneratorTest extends BrowserTestBase {
    */
   public static $modules = ['hal', 'rest', 'node', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/System/RetrieveFileTest.php b/core/modules/system/tests/src/Functional/System/RetrieveFileTest.php
index bcd8f7d3bfb3..25db399666f2 100644
--- a/core/modules/system/tests/src/Functional/System/RetrieveFileTest.php
+++ b/core/modules/system/tests/src/Functional/System/RetrieveFileTest.php
@@ -11,6 +11,11 @@
  */
 class RetrieveFileTest extends BrowserTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Invokes system_retrieve_file() in several scenarios.
    */
diff --git a/core/modules/system/tests/src/Functional/System/ShutdownFunctionsTest.php b/core/modules/system/tests/src/Functional/System/ShutdownFunctionsTest.php
index f5d55be7822a..c7e25bedaf50 100644
--- a/core/modules/system/tests/src/Functional/System/ShutdownFunctionsTest.php
+++ b/core/modules/system/tests/src/Functional/System/ShutdownFunctionsTest.php
@@ -18,6 +18,11 @@ class ShutdownFunctionsTest extends BrowserTestBase {
    */
   public static $modules = ['system_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function tearDown() {
     // This test intentionally throws an exception in a PHP shutdown function.
     // Prevent it from being interpreted as an actual test failure.
diff --git a/core/modules/system/tests/src/Functional/System/SiteMaintenanceTest.php b/core/modules/system/tests/src/Functional/System/SiteMaintenanceTest.php
index 8d2e42d870a5..ec3a4b695002 100644
--- a/core/modules/system/tests/src/Functional/System/SiteMaintenanceTest.php
+++ b/core/modules/system/tests/src/Functional/System/SiteMaintenanceTest.php
@@ -24,6 +24,11 @@ class SiteMaintenanceTest extends BrowserTestBase {
    */
   public static $modules = ['node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected $adminUser;
 
   protected function setUp() {
diff --git a/core/modules/system/tests/src/Functional/System/SitesDirectoryHardeningTest.php b/core/modules/system/tests/src/Functional/System/SitesDirectoryHardeningTest.php
index f08a18d8bc41..ce3ac2a835ab 100644
--- a/core/modules/system/tests/src/Functional/System/SitesDirectoryHardeningTest.php
+++ b/core/modules/system/tests/src/Functional/System/SitesDirectoryHardeningTest.php
@@ -15,6 +15,11 @@
 class SitesDirectoryHardeningTest extends BrowserTestBase {
   use StringTranslationTrait;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the default behavior to restrict directory permissions is enforced.
    *
diff --git a/core/modules/system/tests/src/Functional/System/StatusTest.php b/core/modules/system/tests/src/Functional/System/StatusTest.php
index 845b5a8e92e0..6d4cce4c7b0f 100644
--- a/core/modules/system/tests/src/Functional/System/StatusTest.php
+++ b/core/modules/system/tests/src/Functional/System/StatusTest.php
@@ -18,6 +18,11 @@ class StatusTest extends BrowserTestBase {
    */
   public static $modules = ['update_test_postupdate'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/System/SystemAuthorizeTest.php b/core/modules/system/tests/src/Functional/System/SystemAuthorizeTest.php
index b3f9b310b385..36f7208ea757 100644
--- a/core/modules/system/tests/src/Functional/System/SystemAuthorizeTest.php
+++ b/core/modules/system/tests/src/Functional/System/SystemAuthorizeTest.php
@@ -18,6 +18,11 @@ class SystemAuthorizeTest extends BrowserTestBase {
    */
   public static $modules = ['system_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/system/tests/src/Functional/System/ThemeTest.php b/core/modules/system/tests/src/Functional/System/ThemeTest.php
index 2fa4d917bd5e..2a7b5f898cd8 100644
--- a/core/modules/system/tests/src/Functional/System/ThemeTest.php
+++ b/core/modules/system/tests/src/Functional/System/ThemeTest.php
@@ -33,6 +33,11 @@ class ThemeTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'block', 'file'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/system/tests/src/Functional/System/TokenReplaceWebTest.php b/core/modules/system/tests/src/Functional/System/TokenReplaceWebTest.php
index 450f50704552..de6edc66c004 100644
--- a/core/modules/system/tests/src/Functional/System/TokenReplaceWebTest.php
+++ b/core/modules/system/tests/src/Functional/System/TokenReplaceWebTest.php
@@ -20,6 +20,11 @@ class TokenReplaceWebTest extends BrowserTestBase {
    */
   public static $modules = ['token_test', 'filter', 'node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests a token replacement on an actual website.
    */
diff --git a/core/modules/system/tests/src/Functional/System/TokenScanTest.php b/core/modules/system/tests/src/Functional/System/TokenScanTest.php
index f284aa978b4e..77e28d6edeb7 100644
--- a/core/modules/system/tests/src/Functional/System/TokenScanTest.php
+++ b/core/modules/system/tests/src/Functional/System/TokenScanTest.php
@@ -11,6 +11,11 @@
  */
 class TokenScanTest extends BrowserTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Scans dummy text, then tests the output.
    */
diff --git a/core/modules/system/tests/src/Functional/System/TrustedHostsTest.php b/core/modules/system/tests/src/Functional/System/TrustedHostsTest.php
index 8114ff4d4a31..13f43b80b2e1 100644
--- a/core/modules/system/tests/src/Functional/System/TrustedHostsTest.php
+++ b/core/modules/system/tests/src/Functional/System/TrustedHostsTest.php
@@ -11,6 +11,11 @@
  */
 class TrustedHostsTest extends BrowserTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Theme/EngineNyanCatTest.php b/core/modules/system/tests/src/Functional/Theme/EngineNyanCatTest.php
index 368e1276c7cf..d2b5e3212014 100644
--- a/core/modules/system/tests/src/Functional/Theme/EngineNyanCatTest.php
+++ b/core/modules/system/tests/src/Functional/Theme/EngineNyanCatTest.php
@@ -18,6 +18,11 @@ class EngineNyanCatTest extends BrowserTestBase {
    */
   public static $modules = ['theme_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     \Drupal::service('theme_installer')->install(['test_theme_nyan_cat_engine']);
diff --git a/core/modules/system/tests/src/Functional/Theme/EngineTwigTest.php b/core/modules/system/tests/src/Functional/Theme/EngineTwigTest.php
index c832b2934c77..756e8076dfa5 100644
--- a/core/modules/system/tests/src/Functional/Theme/EngineTwigTest.php
+++ b/core/modules/system/tests/src/Functional/Theme/EngineTwigTest.php
@@ -23,6 +23,11 @@ class EngineTwigTest extends BrowserTestBase {
    */
   public static $modules = ['theme_test', 'twig_theme_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     \Drupal::service('theme_installer')->install(['test_theme']);
diff --git a/core/modules/system/tests/src/Functional/Theme/EntityFilteringThemeTest.php b/core/modules/system/tests/src/Functional/Theme/EntityFilteringThemeTest.php
index a921e873434a..f79f990de245 100644
--- a/core/modules/system/tests/src/Functional/Theme/EntityFilteringThemeTest.php
+++ b/core/modules/system/tests/src/Functional/Theme/EntityFilteringThemeTest.php
@@ -21,6 +21,11 @@ class EntityFilteringThemeTest extends BrowserTestBase {
 
   use CommentTestTrait;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Use the standard profile.
    *
diff --git a/core/modules/system/tests/src/Functional/Theme/ExperimentalThemeTest.php b/core/modules/system/tests/src/Functional/Theme/ExperimentalThemeTest.php
index be37f4a23c32..01409642f53f 100644
--- a/core/modules/system/tests/src/Functional/Theme/ExperimentalThemeTest.php
+++ b/core/modules/system/tests/src/Functional/Theme/ExperimentalThemeTest.php
@@ -18,6 +18,11 @@ class ExperimentalThemeTest extends BrowserTestBase {
    */
   protected $adminUser;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Theme/FastTest.php b/core/modules/system/tests/src/Functional/Theme/FastTest.php
index 977f54dfcedb..80012487b89b 100644
--- a/core/modules/system/tests/src/Functional/Theme/FastTest.php
+++ b/core/modules/system/tests/src/Functional/Theme/FastTest.php
@@ -18,6 +18,11 @@ class FastTest extends BrowserTestBase {
    */
   public static $modules = ['theme_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     $this->account = $this->drupalCreateUser(['access user profiles']);
diff --git a/core/modules/system/tests/src/Functional/Theme/HtmlAttributesTest.php b/core/modules/system/tests/src/Functional/Theme/HtmlAttributesTest.php
index 5aa4be9cc9d3..fccf2ff4d63c 100644
--- a/core/modules/system/tests/src/Functional/Theme/HtmlAttributesTest.php
+++ b/core/modules/system/tests/src/Functional/Theme/HtmlAttributesTest.php
@@ -18,6 +18,11 @@ class HtmlAttributesTest extends BrowserTestBase {
    */
   public static $modules = ['theme_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that attributes in the 'html' and 'body' elements can be altered.
    */
diff --git a/core/modules/system/tests/src/Functional/Theme/ThemeEarlyInitializationTest.php b/core/modules/system/tests/src/Functional/Theme/ThemeEarlyInitializationTest.php
index 040dfabfce91..13d09e63e734 100644
--- a/core/modules/system/tests/src/Functional/Theme/ThemeEarlyInitializationTest.php
+++ b/core/modules/system/tests/src/Functional/Theme/ThemeEarlyInitializationTest.php
@@ -19,6 +19,11 @@ class ThemeEarlyInitializationTest extends BrowserTestBase {
    */
   public static $modules = ['theme_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Test that the theme system can generate output in a request listener.
    */
diff --git a/core/modules/system/tests/src/Functional/Theme/ThemeInfoTest.php b/core/modules/system/tests/src/Functional/Theme/ThemeInfoTest.php
index 8d972c045a1e..05fbca78b02f 100644
--- a/core/modules/system/tests/src/Functional/Theme/ThemeInfoTest.php
+++ b/core/modules/system/tests/src/Functional/Theme/ThemeInfoTest.php
@@ -18,6 +18,11 @@ class ThemeInfoTest extends BrowserTestBase {
    */
   public static $modules = ['theme_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The theme installer used in this test for enabling themes.
    *
diff --git a/core/modules/system/tests/src/Functional/Theme/ThemeSuggestionsAlterTest.php b/core/modules/system/tests/src/Functional/Theme/ThemeSuggestionsAlterTest.php
index cac5e31c1fb4..c521f58e50f7 100644
--- a/core/modules/system/tests/src/Functional/Theme/ThemeSuggestionsAlterTest.php
+++ b/core/modules/system/tests/src/Functional/Theme/ThemeSuggestionsAlterTest.php
@@ -19,6 +19,11 @@ class ThemeSuggestionsAlterTest extends BrowserTestBase {
    */
   public static $modules = ['theme_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     \Drupal::service('theme_installer')->install(['test_theme']);
diff --git a/core/modules/system/tests/src/Functional/Theme/ThemeTest.php b/core/modules/system/tests/src/Functional/Theme/ThemeTest.php
index 019077de55c1..fe4471a2fa28 100644
--- a/core/modules/system/tests/src/Functional/Theme/ThemeTest.php
+++ b/core/modules/system/tests/src/Functional/Theme/ThemeTest.php
@@ -20,6 +20,11 @@ class ThemeTest extends BrowserTestBase {
    */
   public static $modules = ['theme_test', 'node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Theme/ThemeTokenTest.php b/core/modules/system/tests/src/Functional/Theme/ThemeTokenTest.php
index a399bed73d96..c1d8f37d9842 100644
--- a/core/modules/system/tests/src/Functional/Theme/ThemeTokenTest.php
+++ b/core/modules/system/tests/src/Functional/Theme/ThemeTokenTest.php
@@ -18,6 +18,11 @@ class ThemeTokenTest extends BrowserTestBase {
    */
   public static $modules = ['block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Theme/TwigDebugMarkupTest.php b/core/modules/system/tests/src/Functional/Theme/TwigDebugMarkupTest.php
index e67a6341be58..90e5cf842a93 100644
--- a/core/modules/system/tests/src/Functional/Theme/TwigDebugMarkupTest.php
+++ b/core/modules/system/tests/src/Functional/Theme/TwigDebugMarkupTest.php
@@ -19,6 +19,11 @@ class TwigDebugMarkupTest extends BrowserTestBase {
    */
   public static $modules = ['theme_test', 'node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests debug markup added to Twig template output.
    */
diff --git a/core/modules/system/tests/src/Functional/Theme/TwigEnvironmentTest.php b/core/modules/system/tests/src/Functional/Theme/TwigEnvironmentTest.php
index 26f47e9068eb..1043148fd472 100644
--- a/core/modules/system/tests/src/Functional/Theme/TwigEnvironmentTest.php
+++ b/core/modules/system/tests/src/Functional/Theme/TwigEnvironmentTest.php
@@ -16,6 +16,11 @@ class TwigEnvironmentTest extends BrowserTestBase {
    */
   protected static $modules = ['twig_theme_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests template class loading with Twig embed.
    */
diff --git a/core/modules/system/tests/src/Functional/Theme/TwigExtensionTest.php b/core/modules/system/tests/src/Functional/Theme/TwigExtensionTest.php
index 3966d6843a45..04e527e74b9e 100644
--- a/core/modules/system/tests/src/Functional/Theme/TwigExtensionTest.php
+++ b/core/modules/system/tests/src/Functional/Theme/TwigExtensionTest.php
@@ -19,6 +19,11 @@ class TwigExtensionTest extends BrowserTestBase {
    */
   public static $modules = ['theme_test', 'twig_extension_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     \Drupal::service('theme_installer')->install(['test_theme']);
diff --git a/core/modules/system/tests/src/Functional/Theme/TwigLoaderTest.php b/core/modules/system/tests/src/Functional/Theme/TwigLoaderTest.php
index d2b0b5465d2d..1238f2074ace 100644
--- a/core/modules/system/tests/src/Functional/Theme/TwigLoaderTest.php
+++ b/core/modules/system/tests/src/Functional/Theme/TwigLoaderTest.php
@@ -18,6 +18,11 @@ class TwigLoaderTest extends BrowserTestBase {
    */
   public static $modules = ['twig_loader_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests adding an additional twig loader to the loader chain.
    */
diff --git a/core/modules/system/tests/src/Functional/Theme/TwigRegistryLoaderTest.php b/core/modules/system/tests/src/Functional/Theme/TwigRegistryLoaderTest.php
index 4cc7c69f6530..c2c7642e2d4b 100644
--- a/core/modules/system/tests/src/Functional/Theme/TwigRegistryLoaderTest.php
+++ b/core/modules/system/tests/src/Functional/Theme/TwigRegistryLoaderTest.php
@@ -19,6 +19,11 @@ class TwigRegistryLoaderTest extends BrowserTestBase {
    */
   public static $modules = ['twig_theme_test', 'block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * @var \Drupal\Core\Template\TwigEnvironment
    */
diff --git a/core/modules/system/tests/src/Functional/Theme/TwigSettingsTest.php b/core/modules/system/tests/src/Functional/Theme/TwigSettingsTest.php
index d0c333606c3a..2cc8e24d0c58 100644
--- a/core/modules/system/tests/src/Functional/Theme/TwigSettingsTest.php
+++ b/core/modules/system/tests/src/Functional/Theme/TwigSettingsTest.php
@@ -19,6 +19,11 @@ class TwigSettingsTest extends BrowserTestBase {
    */
   public static $modules = ['theme_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Ensures Twig template auto reload setting can be overridden.
    */
diff --git a/core/modules/system/tests/src/Functional/Theme/TwigTransTest.php b/core/modules/system/tests/src/Functional/Theme/TwigTransTest.php
index 75596f7ade96..2b2ae0865f1b 100644
--- a/core/modules/system/tests/src/Functional/Theme/TwigTransTest.php
+++ b/core/modules/system/tests/src/Functional/Theme/TwigTransTest.php
@@ -25,6 +25,11 @@ class TwigTransTest extends BrowserTestBase {
     'language',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * An administrative user for testing.
    *
diff --git a/core/modules/system/tests/src/Functional/Update/AdminThemeUpdateTest.php b/core/modules/system/tests/src/Functional/Update/AdminThemeUpdateTest.php
index 8fa4e07a864f..52bdbb254809 100644
--- a/core/modules/system/tests/src/Functional/Update/AdminThemeUpdateTest.php
+++ b/core/modules/system/tests/src/Functional/Update/AdminThemeUpdateTest.php
@@ -12,6 +12,11 @@
  */
 class AdminThemeUpdateTest extends UpdatePathTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/AutomatedCronUpdateWithAutomatedCronTest.php b/core/modules/system/tests/src/Functional/Update/AutomatedCronUpdateWithAutomatedCronTest.php
index e967f1701f28..3cd9542b01be 100644
--- a/core/modules/system/tests/src/Functional/Update/AutomatedCronUpdateWithAutomatedCronTest.php
+++ b/core/modules/system/tests/src/Functional/Update/AutomatedCronUpdateWithAutomatedCronTest.php
@@ -12,6 +12,11 @@
  */
 class AutomatedCronUpdateWithAutomatedCronTest extends UpdatePathTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/AutomatedCronUpdateWithoutAutomatedCronTest.php b/core/modules/system/tests/src/Functional/Update/AutomatedCronUpdateWithoutAutomatedCronTest.php
index c131c7059238..41243240bd92 100644
--- a/core/modules/system/tests/src/Functional/Update/AutomatedCronUpdateWithoutAutomatedCronTest.php
+++ b/core/modules/system/tests/src/Functional/Update/AutomatedCronUpdateWithoutAutomatedCronTest.php
@@ -12,6 +12,11 @@
  */
 class AutomatedCronUpdateWithoutAutomatedCronTest extends UpdatePathTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/BrokenCacheUpdateTest.php b/core/modules/system/tests/src/Functional/Update/BrokenCacheUpdateTest.php
index 2ad68d2ecf0f..300676a2a38f 100644
--- a/core/modules/system/tests/src/Functional/Update/BrokenCacheUpdateTest.php
+++ b/core/modules/system/tests/src/Functional/Update/BrokenCacheUpdateTest.php
@@ -13,6 +13,11 @@
  */
 class BrokenCacheUpdateTest extends UpdatePathTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/ConfigOverridesUpdateTest.php b/core/modules/system/tests/src/Functional/Update/ConfigOverridesUpdateTest.php
index e18195da10e6..8d565ac85237 100644
--- a/core/modules/system/tests/src/Functional/Update/ConfigOverridesUpdateTest.php
+++ b/core/modules/system/tests/src/Functional/Update/ConfigOverridesUpdateTest.php
@@ -14,6 +14,11 @@
  */
 class ConfigOverridesUpdateTest extends UpdatePathTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/DependencyHookInvocationTest.php b/core/modules/system/tests/src/Functional/Update/DependencyHookInvocationTest.php
index 203d89ef2a70..d967fa86f557 100644
--- a/core/modules/system/tests/src/Functional/Update/DependencyHookInvocationTest.php
+++ b/core/modules/system/tests/src/Functional/Update/DependencyHookInvocationTest.php
@@ -19,6 +19,11 @@ class DependencyHookInvocationTest extends BrowserTestBase {
    */
   public static $modules = ['update_test_0', 'update_test_1', 'update_test_2'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     require_once $this->root . '/core/includes/update.inc';
diff --git a/core/modules/system/tests/src/Functional/Update/DependencyMissingTest.php b/core/modules/system/tests/src/Functional/Update/DependencyMissingTest.php
index e11999a46c23..b7fced809c2b 100644
--- a/core/modules/system/tests/src/Functional/Update/DependencyMissingTest.php
+++ b/core/modules/system/tests/src/Functional/Update/DependencyMissingTest.php
@@ -18,6 +18,11 @@ class DependencyMissingTest extends BrowserTestBase {
    */
   public static $modules = ['update_test_0', 'update_test_2'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     // Only install update_test_2.module, even though its updates have a
     // dependency on update_test_3.module.
diff --git a/core/modules/system/tests/src/Functional/Update/DependencyOrderingTest.php b/core/modules/system/tests/src/Functional/Update/DependencyOrderingTest.php
index 0f168aa78f5c..649f9c93b568 100644
--- a/core/modules/system/tests/src/Functional/Update/DependencyOrderingTest.php
+++ b/core/modules/system/tests/src/Functional/Update/DependencyOrderingTest.php
@@ -18,6 +18,11 @@ class DependencyOrderingTest extends BrowserTestBase {
    */
   public static $modules = ['update_test_0', 'update_test_1', 'update_test_2', 'update_test_3'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     require_once $this->root . '/core/includes/update.inc';
diff --git a/core/modules/system/tests/src/Functional/Update/EntityUpdateAddRevisionDefaultTest.php b/core/modules/system/tests/src/Functional/Update/EntityUpdateAddRevisionDefaultTest.php
index fd8f6cf19245..71375b0e3052 100644
--- a/core/modules/system/tests/src/Functional/Update/EntityUpdateAddRevisionDefaultTest.php
+++ b/core/modules/system/tests/src/Functional/Update/EntityUpdateAddRevisionDefaultTest.php
@@ -18,6 +18,11 @@ class EntityUpdateAddRevisionDefaultTest extends UpdatePathTestBase {
   use EntityDefinitionTestTrait;
   use DbUpdatesTrait;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The state service.
    *
diff --git a/core/modules/system/tests/src/Functional/Update/EntityUpdateAddRevisionTranslationAffectedTest.php b/core/modules/system/tests/src/Functional/Update/EntityUpdateAddRevisionTranslationAffectedTest.php
index 0a3ebbe992ac..2c5fccb048b9 100644
--- a/core/modules/system/tests/src/Functional/Update/EntityUpdateAddRevisionTranslationAffectedTest.php
+++ b/core/modules/system/tests/src/Functional/Update/EntityUpdateAddRevisionTranslationAffectedTest.php
@@ -30,6 +30,11 @@ class EntityUpdateAddRevisionTranslationAffectedTest extends UpdatePathTestBase
    */
   protected static $modules = ['entity_test_update'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/EntityUpdateInitialTest.php b/core/modules/system/tests/src/Functional/Update/EntityUpdateInitialTest.php
index 7a85744b26ff..1d9a698b1b44 100644
--- a/core/modules/system/tests/src/Functional/Update/EntityUpdateInitialTest.php
+++ b/core/modules/system/tests/src/Functional/Update/EntityUpdateInitialTest.php
@@ -14,6 +14,11 @@
  */
 class EntityUpdateInitialTest extends UpdatePathTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/EntityUpdateToPublishableTest.php b/core/modules/system/tests/src/Functional/Update/EntityUpdateToPublishableTest.php
index e887fd561cfa..fd9a1d95e29f 100644
--- a/core/modules/system/tests/src/Functional/Update/EntityUpdateToPublishableTest.php
+++ b/core/modules/system/tests/src/Functional/Update/EntityUpdateToPublishableTest.php
@@ -17,6 +17,11 @@ class EntityUpdateToPublishableTest extends UpdatePathTestBase {
   use EntityDefinitionTestTrait;
   use DbUpdatesTrait;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The entity type manager service.
    *
diff --git a/core/modules/system/tests/src/Functional/Update/FieldSchemaDataUninstallUpdateTest.php b/core/modules/system/tests/src/Functional/Update/FieldSchemaDataUninstallUpdateTest.php
index 1beb62b73de7..e4c90ebe7b03 100644
--- a/core/modules/system/tests/src/Functional/Update/FieldSchemaDataUninstallUpdateTest.php
+++ b/core/modules/system/tests/src/Functional/Update/FieldSchemaDataUninstallUpdateTest.php
@@ -14,6 +14,11 @@
  */
 class FieldSchemaDataUninstallUpdateTest extends UpdatePathTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/FilterHtmlUpdateTest.php b/core/modules/system/tests/src/Functional/Update/FilterHtmlUpdateTest.php
index ea591fcbd8b0..ebcf7f4c01aa 100644
--- a/core/modules/system/tests/src/Functional/Update/FilterHtmlUpdateTest.php
+++ b/core/modules/system/tests/src/Functional/Update/FilterHtmlUpdateTest.php
@@ -13,6 +13,11 @@
  */
 class FilterHtmlUpdateTest extends UpdatePathTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/InstallProfileSystemInstall8300Test.php b/core/modules/system/tests/src/Functional/Update/InstallProfileSystemInstall8300Test.php
index 0a1d03ff3685..ced5847bc6d4 100644
--- a/core/modules/system/tests/src/Functional/Update/InstallProfileSystemInstall8300Test.php
+++ b/core/modules/system/tests/src/Functional/Update/InstallProfileSystemInstall8300Test.php
@@ -13,6 +13,11 @@
  */
 class InstallProfileSystemInstall8300Test extends UpdatePathTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/InvalidUpdateHookTest.php b/core/modules/system/tests/src/Functional/Update/InvalidUpdateHookTest.php
index 44fdf81ab909..51fb4d2807b6 100644
--- a/core/modules/system/tests/src/Functional/Update/InvalidUpdateHookTest.php
+++ b/core/modules/system/tests/src/Functional/Update/InvalidUpdateHookTest.php
@@ -22,6 +22,11 @@ class InvalidUpdateHookTest extends BrowserTestBase {
    */
   public static $modules = ['update_test_invalid_hook', 'update_script_test', 'dblog'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * URL for the upgrade script.
    *
diff --git a/core/modules/system/tests/src/Functional/Update/LocalActionsAndTasksConvertedIntoBlocksUpdateTest.php b/core/modules/system/tests/src/Functional/Update/LocalActionsAndTasksConvertedIntoBlocksUpdateTest.php
index ff4075e9e693..b343d7ac04b5 100644
--- a/core/modules/system/tests/src/Functional/Update/LocalActionsAndTasksConvertedIntoBlocksUpdateTest.php
+++ b/core/modules/system/tests/src/Functional/Update/LocalActionsAndTasksConvertedIntoBlocksUpdateTest.php
@@ -15,6 +15,11 @@
  */
 class LocalActionsAndTasksConvertedIntoBlocksUpdateTest extends UpdatePathTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/MenuBlockPostUpdateTest.php b/core/modules/system/tests/src/Functional/Update/MenuBlockPostUpdateTest.php
index 77ce66dcf4e0..0e4d6c63b3cb 100644
--- a/core/modules/system/tests/src/Functional/Update/MenuBlockPostUpdateTest.php
+++ b/core/modules/system/tests/src/Functional/Update/MenuBlockPostUpdateTest.php
@@ -13,6 +13,11 @@
  */
 class MenuBlockPostUpdateTest extends UpdatePathTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/MenuTreeSerializationTitleFilledTest.php b/core/modules/system/tests/src/Functional/Update/MenuTreeSerializationTitleFilledTest.php
index 58429e3cbc3a..6433bf4a6653 100644
--- a/core/modules/system/tests/src/Functional/Update/MenuTreeSerializationTitleFilledTest.php
+++ b/core/modules/system/tests/src/Functional/Update/MenuTreeSerializationTitleFilledTest.php
@@ -10,6 +10,11 @@
  */
 class MenuTreeSerializationTitleFilledTest extends MenuTreeSerializationTitleTest {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/MenuTreeSerializationTitleTest.php b/core/modules/system/tests/src/Functional/Update/MenuTreeSerializationTitleTest.php
index 1a3fa84f4209..d9572b06e265 100644
--- a/core/modules/system/tests/src/Functional/Update/MenuTreeSerializationTitleTest.php
+++ b/core/modules/system/tests/src/Functional/Update/MenuTreeSerializationTitleTest.php
@@ -13,6 +13,11 @@
  */
 class MenuTreeSerializationTitleTest extends UpdatePathTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/MoveActionsToCoreTest.php b/core/modules/system/tests/src/Functional/Update/MoveActionsToCoreTest.php
index e5c21f23b592..ad0e8259305c 100644
--- a/core/modules/system/tests/src/Functional/Update/MoveActionsToCoreTest.php
+++ b/core/modules/system/tests/src/Functional/Update/MoveActionsToCoreTest.php
@@ -13,6 +13,11 @@
  */
 class MoveActionsToCoreTest extends UpdatePathTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/NoDependenciesUpdateTest.php b/core/modules/system/tests/src/Functional/Update/NoDependenciesUpdateTest.php
index 152d66780039..23c88142b56c 100644
--- a/core/modules/system/tests/src/Functional/Update/NoDependenciesUpdateTest.php
+++ b/core/modules/system/tests/src/Functional/Update/NoDependenciesUpdateTest.php
@@ -12,6 +12,11 @@
  */
 class NoDependenciesUpdateTest extends UpdatePathTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/PageTitleConvertedIntoBlockUpdateTest.php b/core/modules/system/tests/src/Functional/Update/PageTitleConvertedIntoBlockUpdateTest.php
index 6e17506220d0..6548db66f8db 100644
--- a/core/modules/system/tests/src/Functional/Update/PageTitleConvertedIntoBlockUpdateTest.php
+++ b/core/modules/system/tests/src/Functional/Update/PageTitleConvertedIntoBlockUpdateTest.php
@@ -15,6 +15,11 @@
  */
 class PageTitleConvertedIntoBlockUpdateTest extends UpdatePathTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/PathAliasToEntityUpdateTest.php b/core/modules/system/tests/src/Functional/Update/PathAliasToEntityUpdateTest.php
index 0d0a1401b9e7..7a860906e938 100644
--- a/core/modules/system/tests/src/Functional/Update/PathAliasToEntityUpdateTest.php
+++ b/core/modules/system/tests/src/Functional/Update/PathAliasToEntityUpdateTest.php
@@ -13,6 +13,11 @@
  */
 class PathAliasToEntityUpdateTest extends UpdatePathTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/RebuildScriptTest.php b/core/modules/system/tests/src/Functional/Update/RebuildScriptTest.php
index a684b037f71d..d47e9771a4a5 100644
--- a/core/modules/system/tests/src/Functional/Update/RebuildScriptTest.php
+++ b/core/modules/system/tests/src/Functional/Update/RebuildScriptTest.php
@@ -12,6 +12,11 @@
  */
 class RebuildScriptTest extends BrowserTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test redirect in rebuild.php.
    */
diff --git a/core/modules/system/tests/src/Functional/Update/RecalculatedDependencyTest.php b/core/modules/system/tests/src/Functional/Update/RecalculatedDependencyTest.php
index 2cda26e9a140..e2f262a8ebdc 100644
--- a/core/modules/system/tests/src/Functional/Update/RecalculatedDependencyTest.php
+++ b/core/modules/system/tests/src/Functional/Update/RecalculatedDependencyTest.php
@@ -12,6 +12,11 @@
  */
 class RecalculatedDependencyTest extends UpdatePathTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/RemoveResponseGzipFromSystemPerformanceConfigurationTest.php b/core/modules/system/tests/src/Functional/Update/RemoveResponseGzipFromSystemPerformanceConfigurationTest.php
index f7f772b13e7c..9ab66fd26969 100644
--- a/core/modules/system/tests/src/Functional/Update/RemoveResponseGzipFromSystemPerformanceConfigurationTest.php
+++ b/core/modules/system/tests/src/Functional/Update/RemoveResponseGzipFromSystemPerformanceConfigurationTest.php
@@ -12,6 +12,11 @@
  */
 class RemoveResponseGzipFromSystemPerformanceConfigurationTest extends UpdatePathTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/RouterIndexOptimizationFilledTest.php b/core/modules/system/tests/src/Functional/Update/RouterIndexOptimizationFilledTest.php
index 93c9c8e23494..e7454c031045 100644
--- a/core/modules/system/tests/src/Functional/Update/RouterIndexOptimizationFilledTest.php
+++ b/core/modules/system/tests/src/Functional/Update/RouterIndexOptimizationFilledTest.php
@@ -10,6 +10,11 @@
  */
 class RouterIndexOptimizationFilledTest extends RouterIndexOptimizationTest {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/RouterIndexOptimizationTest.php b/core/modules/system/tests/src/Functional/Update/RouterIndexOptimizationTest.php
index f4672b4cd117..884a8dc265b4 100644
--- a/core/modules/system/tests/src/Functional/Update/RouterIndexOptimizationTest.php
+++ b/core/modules/system/tests/src/Functional/Update/RouterIndexOptimizationTest.php
@@ -12,6 +12,11 @@
  */
 class RouterIndexOptimizationTest extends UpdatePathTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/SevenSecondaryLocalTasksConvertedIntoBlockUpdateTest.php b/core/modules/system/tests/src/Functional/Update/SevenSecondaryLocalTasksConvertedIntoBlockUpdateTest.php
index b0a58623a546..f0427d31a2f8 100644
--- a/core/modules/system/tests/src/Functional/Update/SevenSecondaryLocalTasksConvertedIntoBlockUpdateTest.php
+++ b/core/modules/system/tests/src/Functional/Update/SevenSecondaryLocalTasksConvertedIntoBlockUpdateTest.php
@@ -14,6 +14,11 @@
  */
 class SevenSecondaryLocalTasksConvertedIntoBlockUpdateTest extends UpdatePathTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/SiteBrandingConvertedIntoBlockUpdateTest.php b/core/modules/system/tests/src/Functional/Update/SiteBrandingConvertedIntoBlockUpdateTest.php
index 56b988e956d2..4470398b25a3 100644
--- a/core/modules/system/tests/src/Functional/Update/SiteBrandingConvertedIntoBlockUpdateTest.php
+++ b/core/modules/system/tests/src/Functional/Update/SiteBrandingConvertedIntoBlockUpdateTest.php
@@ -12,6 +12,11 @@
  */
 class SiteBrandingConvertedIntoBlockUpdateTest extends UpdatePathTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/StableBaseThemeUpdateTest.php b/core/modules/system/tests/src/Functional/Update/StableBaseThemeUpdateTest.php
index e00a3a94a220..5675cb99bb30 100644
--- a/core/modules/system/tests/src/Functional/Update/StableBaseThemeUpdateTest.php
+++ b/core/modules/system/tests/src/Functional/Update/StableBaseThemeUpdateTest.php
@@ -33,6 +33,11 @@ class StableBaseThemeUpdateTest extends UpdatePathTestBase implements ServicePro
    */
   protected $themeHandler;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/UpdateActionsWithEntityPluginsTest.php b/core/modules/system/tests/src/Functional/Update/UpdateActionsWithEntityPluginsTest.php
index 764c92c5ffb5..db5928ef1a9a 100644
--- a/core/modules/system/tests/src/Functional/Update/UpdateActionsWithEntityPluginsTest.php
+++ b/core/modules/system/tests/src/Functional/Update/UpdateActionsWithEntityPluginsTest.php
@@ -13,6 +13,11 @@
  */
 class UpdateActionsWithEntityPluginsTest extends UpdatePathTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/UpdateCacheTest.php b/core/modules/system/tests/src/Functional/Update/UpdateCacheTest.php
index 1d9765da4ddf..0dc56602c3e9 100644
--- a/core/modules/system/tests/src/Functional/Update/UpdateCacheTest.php
+++ b/core/modules/system/tests/src/Functional/Update/UpdateCacheTest.php
@@ -14,6 +14,11 @@
 class UpdateCacheTest extends BrowserTestBase {
   use RequirementsPageTrait;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that caches are cleared during updates.
    *
diff --git a/core/modules/system/tests/src/Functional/Update/UpdateEntityDisplayTest.php b/core/modules/system/tests/src/Functional/Update/UpdateEntityDisplayTest.php
index 187c7ac9199b..5599462ebdc0 100644
--- a/core/modules/system/tests/src/Functional/Update/UpdateEntityDisplayTest.php
+++ b/core/modules/system/tests/src/Functional/Update/UpdateEntityDisplayTest.php
@@ -14,6 +14,11 @@
  */
 class UpdateEntityDisplayTest extends UpdatePathTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/UpdatePathNewDependencyTest.php b/core/modules/system/tests/src/Functional/Update/UpdatePathNewDependencyTest.php
index 57a53278c434..8f10ef76ce71 100644
--- a/core/modules/system/tests/src/Functional/Update/UpdatePathNewDependencyTest.php
+++ b/core/modules/system/tests/src/Functional/Update/UpdatePathNewDependencyTest.php
@@ -13,6 +13,11 @@
  */
 class UpdatePathNewDependencyTest extends UpdatePathTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/UpdatePathRC1TestBaseFilledTest.php b/core/modules/system/tests/src/Functional/Update/UpdatePathRC1TestBaseFilledTest.php
index 45c3d847758e..c0fcdf4f5814 100644
--- a/core/modules/system/tests/src/Functional/Update/UpdatePathRC1TestBaseFilledTest.php
+++ b/core/modules/system/tests/src/Functional/Update/UpdatePathRC1TestBaseFilledTest.php
@@ -14,6 +14,11 @@
  */
 class UpdatePathRC1TestBaseFilledTest extends UpdatePathRC1TestBaseTest {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/UpdatePathRC1TestBaseTest.php b/core/modules/system/tests/src/Functional/Update/UpdatePathRC1TestBaseTest.php
index af2552492aa4..c3e0cdb05154 100644
--- a/core/modules/system/tests/src/Functional/Update/UpdatePathRC1TestBaseTest.php
+++ b/core/modules/system/tests/src/Functional/Update/UpdatePathRC1TestBaseTest.php
@@ -18,6 +18,11 @@ class UpdatePathRC1TestBaseTest extends UpdatePathTestBase {
    */
   protected static $modules = ['update_test_schema'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/UpdatePathTestBaseFilledTest.php b/core/modules/system/tests/src/Functional/Update/UpdatePathTestBaseFilledTest.php
index 5cc23b007d65..e03073f00bde 100644
--- a/core/modules/system/tests/src/Functional/Update/UpdatePathTestBaseFilledTest.php
+++ b/core/modules/system/tests/src/Functional/Update/UpdatePathTestBaseFilledTest.php
@@ -16,6 +16,11 @@
  */
 class UpdatePathTestBaseFilledTest extends UpdatePathTestBaseTest {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/UpdatePathTestJavaScriptTest.php b/core/modules/system/tests/src/Functional/Update/UpdatePathTestJavaScriptTest.php
index d5bcb16823c9..473c392aa03e 100644
--- a/core/modules/system/tests/src/Functional/Update/UpdatePathTestJavaScriptTest.php
+++ b/core/modules/system/tests/src/Functional/Update/UpdatePathTestJavaScriptTest.php
@@ -12,6 +12,11 @@
  */
 class UpdatePathTestJavaScriptTest extends UpdatePathTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/UpdatePathWithBrokenRoutingFilledTest.php b/core/modules/system/tests/src/Functional/Update/UpdatePathWithBrokenRoutingFilledTest.php
index 4eaec54e366e..6be4f333cb4a 100644
--- a/core/modules/system/tests/src/Functional/Update/UpdatePathWithBrokenRoutingFilledTest.php
+++ b/core/modules/system/tests/src/Functional/Update/UpdatePathWithBrokenRoutingFilledTest.php
@@ -10,6 +10,11 @@
  */
 class UpdatePathWithBrokenRoutingFilledTest extends UpdatePathWithBrokenRoutingTest {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/UpdatePathWithBrokenRoutingTest.php b/core/modules/system/tests/src/Functional/Update/UpdatePathWithBrokenRoutingTest.php
index c54804712cfa..17a70c0215b3 100644
--- a/core/modules/system/tests/src/Functional/Update/UpdatePathWithBrokenRoutingTest.php
+++ b/core/modules/system/tests/src/Functional/Update/UpdatePathWithBrokenRoutingTest.php
@@ -12,6 +12,11 @@
  */
 class UpdatePathWithBrokenRoutingTest extends UpdatePathTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/UpdatePostUpdateFailingTest.php b/core/modules/system/tests/src/Functional/Update/UpdatePostUpdateFailingTest.php
index a01476534c0a..5c6b223d6fbb 100644
--- a/core/modules/system/tests/src/Functional/Update/UpdatePostUpdateFailingTest.php
+++ b/core/modules/system/tests/src/Functional/Update/UpdatePostUpdateFailingTest.php
@@ -12,6 +12,11 @@
  */
 class UpdatePostUpdateFailingTest extends UpdatePathTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/UpdatePostUpdateTest.php b/core/modules/system/tests/src/Functional/Update/UpdatePostUpdateTest.php
index 3e2c46a99c1a..1015e7a138eb 100644
--- a/core/modules/system/tests/src/Functional/Update/UpdatePostUpdateTest.php
+++ b/core/modules/system/tests/src/Functional/Update/UpdatePostUpdateTest.php
@@ -13,6 +13,11 @@
  */
 class UpdatePostUpdateTest extends UpdatePathTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/UpdateSchemaTest.php b/core/modules/system/tests/src/Functional/Update/UpdateSchemaTest.php
index aa28be020d75..193704b2f6dc 100644
--- a/core/modules/system/tests/src/Functional/Update/UpdateSchemaTest.php
+++ b/core/modules/system/tests/src/Functional/Update/UpdateSchemaTest.php
@@ -21,6 +21,11 @@ class UpdateSchemaTest extends BrowserTestBase {
    */
   public static $modules = ['update_test_schema'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * @var \Drupal\user\UserInterface
    */
diff --git a/core/modules/system/tests/src/Functional/Update/UpdateScriptTest.php b/core/modules/system/tests/src/Functional/Update/UpdateScriptTest.php
index 162cbf482cb1..189a1494573d 100644
--- a/core/modules/system/tests/src/Functional/Update/UpdateScriptTest.php
+++ b/core/modules/system/tests/src/Functional/Update/UpdateScriptTest.php
@@ -23,6 +23,11 @@ class UpdateScriptTest extends BrowserTestBase {
    */
   public static $modules = ['update_script_test', 'dblog', 'language'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/Functional/Update/UpdatesWith7xTest.php b/core/modules/system/tests/src/Functional/Update/UpdatesWith7xTest.php
index e4c5635928cf..6b08e685ea3c 100644
--- a/core/modules/system/tests/src/Functional/Update/UpdatesWith7xTest.php
+++ b/core/modules/system/tests/src/Functional/Update/UpdatesWith7xTest.php
@@ -22,6 +22,11 @@ class UpdatesWith7xTest extends BrowserTestBase {
    */
   public static $modules = ['update_test_with_7x'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The URL for the update page.
    *
diff --git a/core/modules/system/tests/src/FunctionalJavascript/Form/ElementsTableSelectTest.php b/core/modules/system/tests/src/FunctionalJavascript/Form/ElementsTableSelectTest.php
index b565bfd74381..560ee6c8bf8a 100644
--- a/core/modules/system/tests/src/FunctionalJavascript/Form/ElementsTableSelectTest.php
+++ b/core/modules/system/tests/src/FunctionalJavascript/Form/ElementsTableSelectTest.php
@@ -16,6 +16,11 @@ class ElementsTableSelectTest extends WebDriverTestBase {
    */
   protected static $modules = ['form_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test the presence of ajax functionality for all options.
    */
diff --git a/core/modules/system/tests/src/FunctionalJavascript/Form/RebuildTest.php b/core/modules/system/tests/src/FunctionalJavascript/Form/RebuildTest.php
index 5bbaa8b909b1..9b38a1625812 100644
--- a/core/modules/system/tests/src/FunctionalJavascript/Form/RebuildTest.php
+++ b/core/modules/system/tests/src/FunctionalJavascript/Form/RebuildTest.php
@@ -21,6 +21,11 @@ class RebuildTest extends WebDriverTestBase {
    */
   protected static $modules = ['node', 'form_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user for testing.
    *
diff --git a/core/modules/system/tests/src/FunctionalJavascript/Form/TriggeringElementTest.php b/core/modules/system/tests/src/FunctionalJavascript/Form/TriggeringElementTest.php
index 41733ec46e3d..3a3840d2d229 100644
--- a/core/modules/system/tests/src/FunctionalJavascript/Form/TriggeringElementTest.php
+++ b/core/modules/system/tests/src/FunctionalJavascript/Form/TriggeringElementTest.php
@@ -16,6 +16,11 @@ class TriggeringElementTest extends WebDriverTestBase {
    */
   protected static $modules = ['form_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the the triggering element when no button information is included.
    *
diff --git a/core/modules/system/tests/src/FunctionalJavascript/FrameworkTest.php b/core/modules/system/tests/src/FunctionalJavascript/FrameworkTest.php
index c23f9847c05b..f2ff799f8812 100644
--- a/core/modules/system/tests/src/FunctionalJavascript/FrameworkTest.php
+++ b/core/modules/system/tests/src/FunctionalJavascript/FrameworkTest.php
@@ -17,6 +17,11 @@ class FrameworkTest extends WebDriverTestBase {
    */
   protected static $modules = ['node', 'ajax_test', 'ajax_forms_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Tests that new JavaScript and CSS files are lazy-loaded on an AJAX request.
    */
diff --git a/core/modules/system/tests/src/FunctionalJavascript/ModalRendererTest.php b/core/modules/system/tests/src/FunctionalJavascript/ModalRendererTest.php
index 3597ba46dd2e..e7ce0429effe 100644
--- a/core/modules/system/tests/src/FunctionalJavascript/ModalRendererTest.php
+++ b/core/modules/system/tests/src/FunctionalJavascript/ModalRendererTest.php
@@ -16,6 +16,11 @@ class ModalRendererTest extends WebDriverTestBase {
    */
   public static $modules = ['system', 'dialog_renderer_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that links respect 'data-dialog-renderer' attribute.
    */
diff --git a/core/modules/system/tests/src/FunctionalJavascript/OffCanvasTest.php b/core/modules/system/tests/src/FunctionalJavascript/OffCanvasTest.php
index 4eac4ec6c7ea..f2d44592c602 100644
--- a/core/modules/system/tests/src/FunctionalJavascript/OffCanvasTest.php
+++ b/core/modules/system/tests/src/FunctionalJavascript/OffCanvasTest.php
@@ -25,6 +25,11 @@ class OffCanvasTest extends OffCanvasTestBase {
     'off_canvas_test',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that non-contextual links will work with the off-canvas dialog.
    *
diff --git a/core/modules/system/tests/src/FunctionalJavascript/System/DateFormatTest.php b/core/modules/system/tests/src/FunctionalJavascript/System/DateFormatTest.php
index 4a0c02b01e89..3460f15b3b81 100644
--- a/core/modules/system/tests/src/FunctionalJavascript/System/DateFormatTest.php
+++ b/core/modules/system/tests/src/FunctionalJavascript/System/DateFormatTest.php
@@ -17,6 +17,11 @@ class DateFormatTest extends WebDriverTestBase {
    */
   protected static $modules = ['block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/system/tests/src/FunctionalJavascript/ThemeSettingsFormTest.php b/core/modules/system/tests/src/FunctionalJavascript/ThemeSettingsFormTest.php
index 00bb56264028..f80ae96facec 100644
--- a/core/modules/system/tests/src/FunctionalJavascript/ThemeSettingsFormTest.php
+++ b/core/modules/system/tests/src/FunctionalJavascript/ThemeSettingsFormTest.php
@@ -20,6 +20,11 @@ class ThemeSettingsFormTest extends WebDriverTestBase {
    */
   public static $modules = ['file'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/taxonomy/tests/src/Functional/EarlyDateTest.php b/core/modules/taxonomy/tests/src/Functional/EarlyDateTest.php
index f0b31aa171c5..74b0093738bd 100644
--- a/core/modules/taxonomy/tests/src/Functional/EarlyDateTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/EarlyDateTest.php
@@ -20,6 +20,11 @@ class EarlyDateTest extends TaxonomyTestBase {
    */
   public static $modules = ['node', 'datetime'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/taxonomy/tests/src/Functional/Hal/TermHalJsonAnonTest.php b/core/modules/taxonomy/tests/src/Functional/Hal/TermHalJsonAnonTest.php
index ee3effc572a2..7a3a57a8cab7 100644
--- a/core/modules/taxonomy/tests/src/Functional/Hal/TermHalJsonAnonTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Hal/TermHalJsonAnonTest.php
@@ -20,6 +20,11 @@ class TermHalJsonAnonTest extends TermResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/taxonomy/tests/src/Functional/Hal/TermHalJsonBasicAuthTest.php b/core/modules/taxonomy/tests/src/Functional/Hal/TermHalJsonBasicAuthTest.php
index 576615607239..43adecebc2b6 100644
--- a/core/modules/taxonomy/tests/src/Functional/Hal/TermHalJsonBasicAuthTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Hal/TermHalJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class TermHalJsonBasicAuthTest extends TermHalJsonAnonTest {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/taxonomy/tests/src/Functional/Hal/TermHalJsonCookieTest.php b/core/modules/taxonomy/tests/src/Functional/Hal/TermHalJsonCookieTest.php
index f949e7a8340a..face86285a48 100644
--- a/core/modules/taxonomy/tests/src/Functional/Hal/TermHalJsonCookieTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Hal/TermHalJsonCookieTest.php
@@ -15,4 +15,9 @@ class TermHalJsonCookieTest extends TermHalJsonAnonTest {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/taxonomy/tests/src/Functional/Hal/VocabularyHalJsonAnonTest.php b/core/modules/taxonomy/tests/src/Functional/Hal/VocabularyHalJsonAnonTest.php
index e2c1bc86bd90..1775ddd2f001 100644
--- a/core/modules/taxonomy/tests/src/Functional/Hal/VocabularyHalJsonAnonTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Hal/VocabularyHalJsonAnonTest.php
@@ -17,6 +17,11 @@ class VocabularyHalJsonAnonTest extends VocabularyResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/taxonomy/tests/src/Functional/Hal/VocabularyHalJsonBasicAuthTest.php b/core/modules/taxonomy/tests/src/Functional/Hal/VocabularyHalJsonBasicAuthTest.php
index d8c17e6d3a0f..ad9d23403698 100644
--- a/core/modules/taxonomy/tests/src/Functional/Hal/VocabularyHalJsonBasicAuthTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Hal/VocabularyHalJsonBasicAuthTest.php
@@ -17,6 +17,11 @@ class VocabularyHalJsonBasicAuthTest extends VocabularyResourceTestBase {
    */
   public static $modules = ['hal', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/taxonomy/tests/src/Functional/Hal/VocabularyHalJsonCookieTest.php b/core/modules/taxonomy/tests/src/Functional/Hal/VocabularyHalJsonCookieTest.php
index 13a44dbb93e5..3e8b3cc7d413 100644
--- a/core/modules/taxonomy/tests/src/Functional/Hal/VocabularyHalJsonCookieTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Hal/VocabularyHalJsonCookieTest.php
@@ -17,6 +17,11 @@ class VocabularyHalJsonCookieTest extends VocabularyResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/taxonomy/tests/src/Functional/LoadMultipleTest.php b/core/modules/taxonomy/tests/src/Functional/LoadMultipleTest.php
index 14ce5548c678..5a05fe6363bf 100644
--- a/core/modules/taxonomy/tests/src/Functional/LoadMultipleTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/LoadMultipleTest.php
@@ -12,6 +12,11 @@
  */
 class LoadMultipleTest extends TaxonomyTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     $this->drupalLogin($this->drupalCreateUser(['administer taxonomy']));
diff --git a/core/modules/taxonomy/tests/src/Functional/Rest/TermJsonAnonTest.php b/core/modules/taxonomy/tests/src/Functional/Rest/TermJsonAnonTest.php
index 7d87337597c1..19aef9697a81 100644
--- a/core/modules/taxonomy/tests/src/Functional/Rest/TermJsonAnonTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Rest/TermJsonAnonTest.php
@@ -21,4 +21,9 @@ class TermJsonAnonTest extends TermResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/taxonomy/tests/src/Functional/Rest/TermJsonBasicAuthTest.php b/core/modules/taxonomy/tests/src/Functional/Rest/TermJsonBasicAuthTest.php
index 959e2bb187a9..8bb4c921cf2c 100644
--- a/core/modules/taxonomy/tests/src/Functional/Rest/TermJsonBasicAuthTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Rest/TermJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class TermJsonBasicAuthTest extends TermResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/taxonomy/tests/src/Functional/Rest/TermJsonCookieTest.php b/core/modules/taxonomy/tests/src/Functional/Rest/TermJsonCookieTest.php
index 88dd70c60640..6a721186a81e 100644
--- a/core/modules/taxonomy/tests/src/Functional/Rest/TermJsonCookieTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Rest/TermJsonCookieTest.php
@@ -26,4 +26,9 @@ class TermJsonCookieTest extends TermResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/taxonomy/tests/src/Functional/Rest/TermXmlAnonTest.php b/core/modules/taxonomy/tests/src/Functional/Rest/TermXmlAnonTest.php
index 69abeaf210a8..ff05095d3d60 100644
--- a/core/modules/taxonomy/tests/src/Functional/Rest/TermXmlAnonTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Rest/TermXmlAnonTest.php
@@ -23,6 +23,11 @@ class TermXmlAnonTest extends TermResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/taxonomy/tests/src/Functional/Rest/TermXmlBasicAuthTest.php b/core/modules/taxonomy/tests/src/Functional/Rest/TermXmlBasicAuthTest.php
index 8eacb85c1c08..f907dddb0b34 100644
--- a/core/modules/taxonomy/tests/src/Functional/Rest/TermXmlBasicAuthTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Rest/TermXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class TermXmlBasicAuthTest extends TermResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/taxonomy/tests/src/Functional/Rest/TermXmlCookieTest.php b/core/modules/taxonomy/tests/src/Functional/Rest/TermXmlCookieTest.php
index 3de95fdabab3..a83fe821fdc0 100644
--- a/core/modules/taxonomy/tests/src/Functional/Rest/TermXmlCookieTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Rest/TermXmlCookieTest.php
@@ -18,6 +18,11 @@ class TermXmlCookieTest extends TermResourceTestBase {
    */
   protected static $format = 'xml';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/taxonomy/tests/src/Functional/Rest/VocabularyJsonAnonTest.php b/core/modules/taxonomy/tests/src/Functional/Rest/VocabularyJsonAnonTest.php
index a85da938272e..956a3079e4fa 100644
--- a/core/modules/taxonomy/tests/src/Functional/Rest/VocabularyJsonAnonTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Rest/VocabularyJsonAnonTest.php
@@ -21,6 +21,11 @@ class VocabularyJsonAnonTest extends VocabularyResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Disable the GET test coverage due to bug in taxonomy module.
    * @todo Fix in https://www.drupal.org/node/2805281: remove this override.
diff --git a/core/modules/taxonomy/tests/src/Functional/Rest/VocabularyJsonBasicAuthTest.php b/core/modules/taxonomy/tests/src/Functional/Rest/VocabularyJsonBasicAuthTest.php
index ec0d67e2b2ed..4bcb94e93b76 100644
--- a/core/modules/taxonomy/tests/src/Functional/Rest/VocabularyJsonBasicAuthTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Rest/VocabularyJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class VocabularyJsonBasicAuthTest extends VocabularyResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/taxonomy/tests/src/Functional/Rest/VocabularyJsonCookieTest.php b/core/modules/taxonomy/tests/src/Functional/Rest/VocabularyJsonCookieTest.php
index 51c79a6a8c45..63c2f3771968 100644
--- a/core/modules/taxonomy/tests/src/Functional/Rest/VocabularyJsonCookieTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Rest/VocabularyJsonCookieTest.php
@@ -26,4 +26,9 @@ class VocabularyJsonCookieTest extends VocabularyResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/taxonomy/tests/src/Functional/Rest/VocabularyXmlAnonTest.php b/core/modules/taxonomy/tests/src/Functional/Rest/VocabularyXmlAnonTest.php
index ac8da3d741ef..64ab45b93606 100644
--- a/core/modules/taxonomy/tests/src/Functional/Rest/VocabularyXmlAnonTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Rest/VocabularyXmlAnonTest.php
@@ -23,4 +23,9 @@ class VocabularyXmlAnonTest extends VocabularyResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/taxonomy/tests/src/Functional/Rest/VocabularyXmlBasicAuthTest.php b/core/modules/taxonomy/tests/src/Functional/Rest/VocabularyXmlBasicAuthTest.php
index 52b3741a9aff..b0a459098267 100644
--- a/core/modules/taxonomy/tests/src/Functional/Rest/VocabularyXmlBasicAuthTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Rest/VocabularyXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class VocabularyXmlBasicAuthTest extends VocabularyResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/taxonomy/tests/src/Functional/Rest/VocabularyXmlCookieTest.php b/core/modules/taxonomy/tests/src/Functional/Rest/VocabularyXmlCookieTest.php
index 51e7e20e49dd..1b87db1b906f 100644
--- a/core/modules/taxonomy/tests/src/Functional/Rest/VocabularyXmlCookieTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Rest/VocabularyXmlCookieTest.php
@@ -28,4 +28,9 @@ class VocabularyXmlCookieTest extends VocabularyResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/taxonomy/tests/src/Functional/RssTest.php b/core/modules/taxonomy/tests/src/Functional/RssTest.php
index 00e380e048ed..b0488f1d0f0a 100644
--- a/core/modules/taxonomy/tests/src/Functional/RssTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/RssTest.php
@@ -20,6 +20,11 @@ class RssTest extends TaxonomyTestBase {
    */
   public static $modules = ['node', 'field_ui', 'views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Vocabulary for testing.
    *
diff --git a/core/modules/taxonomy/tests/src/Functional/TaxonomyImageTest.php b/core/modules/taxonomy/tests/src/Functional/TaxonomyImageTest.php
index a22cbe179ca8..6bd4ef5bca5d 100644
--- a/core/modules/taxonomy/tests/src/Functional/TaxonomyImageTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/TaxonomyImageTest.php
@@ -34,6 +34,11 @@ class TaxonomyImageTest extends TaxonomyTestBase {
    */
   public static $modules = ['image'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/taxonomy/tests/src/Functional/TaxonomyTermIndentationTest.php b/core/modules/taxonomy/tests/src/Functional/TaxonomyTermIndentationTest.php
index 89de4c54989f..8e580023e79e 100644
--- a/core/modules/taxonomy/tests/src/Functional/TaxonomyTermIndentationTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/TaxonomyTermIndentationTest.php
@@ -16,6 +16,11 @@ class TaxonomyTermIndentationTest extends TaxonomyTestBase {
    */
   public static $modules = ['taxonomy'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Vocabulary for testing.
    *
diff --git a/core/modules/taxonomy/tests/src/Functional/TaxonomyTermPagerTest.php b/core/modules/taxonomy/tests/src/Functional/TaxonomyTermPagerTest.php
index 6244c68b55df..99c80db177ba 100644
--- a/core/modules/taxonomy/tests/src/Functional/TaxonomyTermPagerTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/TaxonomyTermPagerTest.php
@@ -16,6 +16,11 @@ class TaxonomyTermPagerTest extends TaxonomyTestBase {
    */
   public static $modules = ['taxonomy'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Vocabulary for testing.
    *
diff --git a/core/modules/taxonomy/tests/src/Functional/TermAccessTest.php b/core/modules/taxonomy/tests/src/Functional/TermAccessTest.php
index 4836fcd6555c..a69fdf144d41 100644
--- a/core/modules/taxonomy/tests/src/Functional/TermAccessTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/TermAccessTest.php
@@ -15,6 +15,11 @@ class TermAccessTest extends TaxonomyTestBase {
 
   use AssertPageCacheContextsAndTagsTrait;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test access control functionality for taxonomy terms.
    */
diff --git a/core/modules/taxonomy/tests/src/Functional/TermAutocompleteTest.php b/core/modules/taxonomy/tests/src/Functional/TermAutocompleteTest.php
index 6304976176a7..d3b3845d8a6c 100644
--- a/core/modules/taxonomy/tests/src/Functional/TermAutocompleteTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/TermAutocompleteTest.php
@@ -23,6 +23,11 @@ class TermAutocompleteTest extends TaxonomyTestBase {
    */
   public static $modules = ['node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The vocabulary.
    *
diff --git a/core/modules/taxonomy/tests/src/Functional/TermCacheTagsTest.php b/core/modules/taxonomy/tests/src/Functional/TermCacheTagsTest.php
index 378d02c755f0..52fef002993f 100644
--- a/core/modules/taxonomy/tests/src/Functional/TermCacheTagsTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/TermCacheTagsTest.php
@@ -18,6 +18,11 @@ class TermCacheTagsTest extends EntityWithUriCacheTagsTestBase {
    */
   public static $modules = ['taxonomy'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/taxonomy/tests/src/Functional/TermContextualLinksTest.php b/core/modules/taxonomy/tests/src/Functional/TermContextualLinksTest.php
index 997e698b9eff..e24ca634f465 100644
--- a/core/modules/taxonomy/tests/src/Functional/TermContextualLinksTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/TermContextualLinksTest.php
@@ -16,6 +16,11 @@ class TermContextualLinksTest extends TaxonomyTestBase {
     'contextual',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests contextual links.
    */
diff --git a/core/modules/taxonomy/tests/src/Functional/TermIndexTest.php b/core/modules/taxonomy/tests/src/Functional/TermIndexTest.php
index 78618823262a..dd240bee6dbc 100644
--- a/core/modules/taxonomy/tests/src/Functional/TermIndexTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/TermIndexTest.php
@@ -20,6 +20,11 @@ class TermIndexTest extends TaxonomyTestBase {
    */
   public static $modules = ['views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Vocabulary for testing.
    *
diff --git a/core/modules/taxonomy/tests/src/Functional/TermLanguageTest.php b/core/modules/taxonomy/tests/src/Functional/TermLanguageTest.php
index f60e77e534a6..bc6230c2894d 100644
--- a/core/modules/taxonomy/tests/src/Functional/TermLanguageTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/TermLanguageTest.php
@@ -14,6 +14,11 @@ class TermLanguageTest extends TaxonomyTestBase {
 
   public static $modules = ['language'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Vocabulary for testing.
    *
diff --git a/core/modules/taxonomy/tests/src/Functional/TermTest.php b/core/modules/taxonomy/tests/src/Functional/TermTest.php
index d0f5b306778d..a15a44da66b1 100644
--- a/core/modules/taxonomy/tests/src/Functional/TermTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/TermTest.php
@@ -36,6 +36,11 @@ class TermTest extends TaxonomyTestBase {
    */
   public static $modules = ['block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/taxonomy/tests/src/Functional/TermTranslationFieldViewTest.php b/core/modules/taxonomy/tests/src/Functional/TermTranslationFieldViewTest.php
index 236ac7055335..1153b8ec441f 100644
--- a/core/modules/taxonomy/tests/src/Functional/TermTranslationFieldViewTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/TermTranslationFieldViewTest.php
@@ -41,6 +41,11 @@ class TermTranslationFieldViewTest extends TaxonomyTestBase {
    */
   public static $modules = ['language', 'content_translation', 'taxonomy'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     $this->setupLanguages();
diff --git a/core/modules/taxonomy/tests/src/Functional/TermTranslationTest.php b/core/modules/taxonomy/tests/src/Functional/TermTranslationTest.php
index 227a589cc87e..a9ae460f81bb 100644
--- a/core/modules/taxonomy/tests/src/Functional/TermTranslationTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/TermTranslationTest.php
@@ -38,6 +38,11 @@ class TermTranslationTest extends TaxonomyTestBase {
    */
   public static $modules = ['taxonomy', 'language', 'content_translation'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/taxonomy/tests/src/Functional/TermTranslationUITest.php b/core/modules/taxonomy/tests/src/Functional/TermTranslationUITest.php
index a71215eda8f4..74b7b2467c34 100644
--- a/core/modules/taxonomy/tests/src/Functional/TermTranslationUITest.php
+++ b/core/modules/taxonomy/tests/src/Functional/TermTranslationUITest.php
@@ -28,6 +28,11 @@ class TermTranslationUITest extends ContentTranslationUITestBase {
    */
   public static $modules = ['language', 'content_translation', 'taxonomy'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   protected function setUp() {
     $this->entityTypeId = 'taxonomy_term';
     $this->bundle = 'tags';
diff --git a/core/modules/taxonomy/tests/src/Functional/ThemeTest.php b/core/modules/taxonomy/tests/src/Functional/ThemeTest.php
index bf6c6b57daf3..e0a8774fc92d 100644
--- a/core/modules/taxonomy/tests/src/Functional/ThemeTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/ThemeTest.php
@@ -9,6 +9,11 @@
  */
 class ThemeTest extends TaxonomyTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/taxonomy/tests/src/Functional/TokenReplaceTest.php b/core/modules/taxonomy/tests/src/Functional/TokenReplaceTest.php
index 5bd236b64287..e8c5b322bfd2 100644
--- a/core/modules/taxonomy/tests/src/Functional/TokenReplaceTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/TokenReplaceTest.php
@@ -28,6 +28,11 @@ class TokenReplaceTest extends TaxonomyTestBase {
    */
   protected $fieldName;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     $this->drupalLogin($this->drupalCreateUser(['administer taxonomy', 'bypass node access']));
diff --git a/core/modules/taxonomy/tests/src/Functional/Views/RelationshipNodeTermDataTest.php b/core/modules/taxonomy/tests/src/Functional/Views/RelationshipNodeTermDataTest.php
index 3469870fa43f..c78a511b3c76 100644
--- a/core/modules/taxonomy/tests/src/Functional/Views/RelationshipNodeTermDataTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Views/RelationshipNodeTermDataTest.php
@@ -18,6 +18,11 @@ class RelationshipNodeTermDataTest extends TaxonomyTestBase {
    */
   public static $testViews = ['test_taxonomy_node_term_data'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   public function testViewsHandlerRelationshipNodeTermData() {
     $view = Views::getView('test_taxonomy_node_term_data');
     // Tests \Drupal\taxonomy\Plugin\views\relationship\NodeTermData::calculateDependencies().
diff --git a/core/modules/taxonomy/tests/src/Functional/Views/RelationshipRepresentativeNodeTest.php b/core/modules/taxonomy/tests/src/Functional/Views/RelationshipRepresentativeNodeTest.php
index d1de82efedab..f43381524586 100644
--- a/core/modules/taxonomy/tests/src/Functional/Views/RelationshipRepresentativeNodeTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Views/RelationshipRepresentativeNodeTest.php
@@ -18,6 +18,11 @@ class RelationshipRepresentativeNodeTest extends TaxonomyTestBase {
    */
   public static $testViews = ['test_groupwise_term'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the relationship.
    */
diff --git a/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyDefaultArgumentTest.php b/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyDefaultArgumentTest.php
index d2eb21625d36..e5bb15bffcea 100644
--- a/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyDefaultArgumentTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyDefaultArgumentTest.php
@@ -16,6 +16,11 @@ class TaxonomyDefaultArgumentTest extends TaxonomyTestBase {
    */
   public static $testViews = ['taxonomy_default_argument_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests escaping of page title when the taxonomy plugin provides it.
    */
diff --git a/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyFieldAllTermsTest.php b/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyFieldAllTermsTest.php
index de313e087f10..67bf8e5f34a0 100644
--- a/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyFieldAllTermsTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyFieldAllTermsTest.php
@@ -19,6 +19,11 @@ class TaxonomyFieldAllTermsTest extends TaxonomyTestBase {
    */
   public static $testViews = ['taxonomy_all_terms_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the "all terms" field handler.
    */
diff --git a/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyFieldFilterTest.php b/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyFieldFilterTest.php
index 1b8bbcaa517e..5df90a6893f3 100644
--- a/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyFieldFilterTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyFieldFilterTest.php
@@ -24,6 +24,11 @@ class TaxonomyFieldFilterTest extends ViewTestBase {
    */
   public static $modules = ['language', 'taxonomy', 'taxonomy_test_views', 'text', 'views', 'node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyIndexTidUiTest.php b/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyIndexTidUiTest.php
index a269c8fe0df8..b2325fdf82d2 100644
--- a/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyIndexTidUiTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyIndexTidUiTest.php
@@ -26,6 +26,11 @@ class TaxonomyIndexTidUiTest extends UITestBase {
    */
   public static $testViews = ['test_filter_taxonomy_index_tid', 'test_taxonomy_term_name'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Modules to enable.
    *
diff --git a/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyParentUITest.php b/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyParentUITest.php
index d8ab8ea12116..44f9eb5cf6ee 100644
--- a/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyParentUITest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyParentUITest.php
@@ -20,6 +20,11 @@ class TaxonomyParentUITest extends UITestBase {
    */
   public static $testViews = ['test_taxonomy_parent'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Modules to enable.
    *
diff --git a/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyRelationshipTest.php b/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyRelationshipTest.php
index 329996490952..20f467417e94 100644
--- a/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyRelationshipTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyRelationshipTest.php
@@ -27,6 +27,11 @@ class TaxonomyRelationshipTest extends TaxonomyTestBase {
    */
   public static $testViews = ['test_taxonomy_term_relationship'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyTermArgumentDepthTest.php b/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyTermArgumentDepthTest.php
index 3505784a0785..0107dea661b2 100644
--- a/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyTermArgumentDepthTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyTermArgumentDepthTest.php
@@ -14,6 +14,11 @@ class TaxonomyTermArgumentDepthTest extends TaxonomyTestBase {
    */
   public static $modules = ['taxonomy', 'taxonomy_test_views', 'views', 'node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyTermFilterDepthTest.php b/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyTermFilterDepthTest.php
index 4d7a4fdf03c6..5cc1ad93dbf5 100644
--- a/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyTermFilterDepthTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyTermFilterDepthTest.php
@@ -16,6 +16,11 @@ class TaxonomyTermFilterDepthTest extends TaxonomyTestBase {
    */
   public static $modules = ['taxonomy', 'taxonomy_test_views', 'views', 'node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyTermViewTest.php b/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyTermViewTest.php
index 42bfc4989c90..13cd7286b11a 100644
--- a/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyTermViewTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyTermViewTest.php
@@ -23,6 +23,11 @@ class TaxonomyTermViewTest extends TaxonomyTestBase {
    */
   public static $modules = ['taxonomy', 'views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * An user with permissions to administer taxonomy.
    *
diff --git a/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyVocabularyArgumentTest.php b/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyVocabularyArgumentTest.php
index 8b1d58cf29e6..1ee93b6805b3 100644
--- a/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyVocabularyArgumentTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Views/TaxonomyVocabularyArgumentTest.php
@@ -16,6 +16,11 @@ class TaxonomyVocabularyArgumentTest extends TaxonomyTestBase {
    */
   public static $modules = ['taxonomy', 'taxonomy_test_views', 'views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/taxonomy/tests/src/Functional/Views/TermDisplayConfigurableTest.php b/core/modules/taxonomy/tests/src/Functional/Views/TermDisplayConfigurableTest.php
index 5c89c7fb2c27..e1a24aaef208 100644
--- a/core/modules/taxonomy/tests/src/Functional/Views/TermDisplayConfigurableTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Views/TermDisplayConfigurableTest.php
@@ -9,6 +9,11 @@
  */
 class TermDisplayConfigurableTest extends TaxonomyTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/taxonomy/tests/src/Functional/Views/TermNameFieldTest.php b/core/modules/taxonomy/tests/src/Functional/Views/TermNameFieldTest.php
index 6fbe0c0b2b5d..baad381aae8f 100644
--- a/core/modules/taxonomy/tests/src/Functional/Views/TermNameFieldTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/Views/TermNameFieldTest.php
@@ -18,6 +18,11 @@ class TermNameFieldTest extends TaxonomyTestBase {
    */
   public static $testViews = ['test_taxonomy_term_name'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests term name field plugin functionality.
    */
diff --git a/core/modules/taxonomy/tests/src/Functional/VocabularyLanguageTest.php b/core/modules/taxonomy/tests/src/Functional/VocabularyLanguageTest.php
index c94d64e287d8..17a096b2cbe6 100644
--- a/core/modules/taxonomy/tests/src/Functional/VocabularyLanguageTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/VocabularyLanguageTest.php
@@ -14,6 +14,11 @@ class VocabularyLanguageTest extends TaxonomyTestBase {
 
   public static $modules = ['language'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/taxonomy/tests/src/Functional/VocabularyPermissionsTest.php b/core/modules/taxonomy/tests/src/Functional/VocabularyPermissionsTest.php
index bb94a96da67a..174feab7f75b 100644
--- a/core/modules/taxonomy/tests/src/Functional/VocabularyPermissionsTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/VocabularyPermissionsTest.php
@@ -18,6 +18,11 @@ class VocabularyPermissionsTest extends TaxonomyTestBase {
    */
   public static $modules = ['help'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/taxonomy/tests/src/Functional/VocabularySerializationTest.php b/core/modules/taxonomy/tests/src/Functional/VocabularySerializationTest.php
index b9aba8a7989e..bb43476cf27a 100644
--- a/core/modules/taxonomy/tests/src/Functional/VocabularySerializationTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/VocabularySerializationTest.php
@@ -23,6 +23,11 @@ class VocabularySerializationTest extends BrowserTestBase {
    */
   public static $modules = ['taxonomy', 'vocabulary_serialization_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/taxonomy/tests/src/Functional/VocabularyTranslationTest.php b/core/modules/taxonomy/tests/src/Functional/VocabularyTranslationTest.php
index aa98ac33300b..16ba9c646540 100644
--- a/core/modules/taxonomy/tests/src/Functional/VocabularyTranslationTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/VocabularyTranslationTest.php
@@ -14,6 +14,11 @@ class VocabularyTranslationTest extends TaxonomyTestBase {
    */
   public static $modules = ['content_translation', 'language'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/taxonomy/tests/src/Functional/VocabularyUiTest.php b/core/modules/taxonomy/tests/src/Functional/VocabularyUiTest.php
index 7cddcc58199a..1a738958dbf3 100644
--- a/core/modules/taxonomy/tests/src/Functional/VocabularyUiTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/VocabularyUiTest.php
@@ -19,6 +19,11 @@ class VocabularyUiTest extends TaxonomyTestBase {
    */
   protected $vocabulary;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     $this->drupalLogin($this->drupalCreateUser(['administer taxonomy']));
diff --git a/core/modules/telephone/tests/src/Functional/TelephoneFieldTest.php b/core/modules/telephone/tests/src/Functional/TelephoneFieldTest.php
index 843bf4472b49..40607d2359b3 100644
--- a/core/modules/telephone/tests/src/Functional/TelephoneFieldTest.php
+++ b/core/modules/telephone/tests/src/Functional/TelephoneFieldTest.php
@@ -24,6 +24,11 @@ class TelephoneFieldTest extends BrowserTestBase {
     'telephone',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with permission to create articles.
    *
diff --git a/core/modules/text/tests/src/Functional/TextFieldTest.php b/core/modules/text/tests/src/Functional/TextFieldTest.php
index 489d70fc593b..3eba8c7e574b 100644
--- a/core/modules/text/tests/src/Functional/TextFieldTest.php
+++ b/core/modules/text/tests/src/Functional/TextFieldTest.php
@@ -28,6 +28,11 @@ class TextFieldTest extends StringFieldTest {
    */
   protected $adminUser;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/text/tests/src/Functional/TextRequiredSummaryUpdateTest.php b/core/modules/text/tests/src/Functional/TextRequiredSummaryUpdateTest.php
index 62b22ef26377..ba94af28cc63 100644
--- a/core/modules/text/tests/src/Functional/TextRequiredSummaryUpdateTest.php
+++ b/core/modules/text/tests/src/Functional/TextRequiredSummaryUpdateTest.php
@@ -14,6 +14,11 @@
  */
 class TextRequiredSummaryUpdateTest extends UpdatePathTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/text/tests/src/FunctionalJavascript/TextareaWithSummaryTest.php b/core/modules/text/tests/src/FunctionalJavascript/TextareaWithSummaryTest.php
index 88153abce5b4..9d939eead4e4 100644
--- a/core/modules/text/tests/src/FunctionalJavascript/TextareaWithSummaryTest.php
+++ b/core/modules/text/tests/src/FunctionalJavascript/TextareaWithSummaryTest.php
@@ -17,6 +17,11 @@ class TextareaWithSummaryTest extends WebDriverTestBase {
    */
   public static $modules = ['text', 'node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/toolbar/tests/src/Functional/ToolbarAdminMenuTest.php b/core/modules/toolbar/tests/src/Functional/ToolbarAdminMenuTest.php
index fd27b4ba3db0..7260d2395796 100644
--- a/core/modules/toolbar/tests/src/Functional/ToolbarAdminMenuTest.php
+++ b/core/modules/toolbar/tests/src/Functional/ToolbarAdminMenuTest.php
@@ -56,6 +56,11 @@ class ToolbarAdminMenuTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'block', 'menu_ui', 'user', 'taxonomy', 'toolbar', 'language', 'test_page_test', 'locale'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/toolbar/tests/src/Functional/ToolbarCacheContextsTest.php b/core/modules/toolbar/tests/src/Functional/ToolbarCacheContextsTest.php
index 023254547321..8b564cca07d6 100644
--- a/core/modules/toolbar/tests/src/Functional/ToolbarCacheContextsTest.php
+++ b/core/modules/toolbar/tests/src/Functional/ToolbarCacheContextsTest.php
@@ -23,6 +23,11 @@ class ToolbarCacheContextsTest extends BrowserTestBase {
    */
   public static $modules = ['toolbar', 'test_page_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * An authenticated user to use for testing.
    *
diff --git a/core/modules/toolbar/tests/src/Functional/ToolbarHookToolbarTest.php b/core/modules/toolbar/tests/src/Functional/ToolbarHookToolbarTest.php
index f3d3ce6118db..3153bbe21600 100644
--- a/core/modules/toolbar/tests/src/Functional/ToolbarHookToolbarTest.php
+++ b/core/modules/toolbar/tests/src/Functional/ToolbarHookToolbarTest.php
@@ -25,6 +25,11 @@ class ToolbarHookToolbarTest extends BrowserTestBase {
    */
   public static $modules = ['toolbar', 'toolbar_test', 'test_page_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/toolbar/tests/src/Functional/ToolbarMenuTranslationTest.php b/core/modules/toolbar/tests/src/Functional/ToolbarMenuTranslationTest.php
index 995d49ee3869..57336e04b2f8 100644
--- a/core/modules/toolbar/tests/src/Functional/ToolbarMenuTranslationTest.php
+++ b/core/modules/toolbar/tests/src/Functional/ToolbarMenuTranslationTest.php
@@ -25,6 +25,11 @@ class ToolbarMenuTranslationTest extends BrowserTestBase {
    */
   public static $modules = ['toolbar', 'toolbar_test', 'locale', 'locale_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/toolbar/tests/src/FunctionalJavascript/ToolbarIntegrationTest.php b/core/modules/toolbar/tests/src/FunctionalJavascript/ToolbarIntegrationTest.php
index fd163985e750..8ee38bdb16a5 100644
--- a/core/modules/toolbar/tests/src/FunctionalJavascript/ToolbarIntegrationTest.php
+++ b/core/modules/toolbar/tests/src/FunctionalJavascript/ToolbarIntegrationTest.php
@@ -16,6 +16,11 @@ class ToolbarIntegrationTest extends WebDriverTestBase {
    */
   public static $modules = ['toolbar', 'node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests if the toolbar can be toggled with JavaScript.
    */
diff --git a/core/modules/tour/tests/src/Functional/Hal/TourHalJsonAnonTest.php b/core/modules/tour/tests/src/Functional/Hal/TourHalJsonAnonTest.php
index 1461fc1a88d9..b4e37290cd08 100644
--- a/core/modules/tour/tests/src/Functional/Hal/TourHalJsonAnonTest.php
+++ b/core/modules/tour/tests/src/Functional/Hal/TourHalJsonAnonTest.php
@@ -17,6 +17,11 @@ class TourHalJsonAnonTest extends TourResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/tour/tests/src/Functional/Hal/TourHalJsonBasicAuthTest.php b/core/modules/tour/tests/src/Functional/Hal/TourHalJsonBasicAuthTest.php
index c79f55e48e67..6d70a323db77 100644
--- a/core/modules/tour/tests/src/Functional/Hal/TourHalJsonBasicAuthTest.php
+++ b/core/modules/tour/tests/src/Functional/Hal/TourHalJsonBasicAuthTest.php
@@ -17,6 +17,11 @@ class TourHalJsonBasicAuthTest extends TourResourceTestBase {
    */
   public static $modules = ['hal', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/tour/tests/src/Functional/Hal/TourHalJsonCookieTest.php b/core/modules/tour/tests/src/Functional/Hal/TourHalJsonCookieTest.php
index 6a7737db0810..43ea4ea1b4c2 100644
--- a/core/modules/tour/tests/src/Functional/Hal/TourHalJsonCookieTest.php
+++ b/core/modules/tour/tests/src/Functional/Hal/TourHalJsonCookieTest.php
@@ -17,6 +17,11 @@ class TourHalJsonCookieTest extends TourResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/tour/tests/src/Functional/Rest/TourJsonAnonTest.php b/core/modules/tour/tests/src/Functional/Rest/TourJsonAnonTest.php
index 530fbe70b86c..0a171f248572 100644
--- a/core/modules/tour/tests/src/Functional/Rest/TourJsonAnonTest.php
+++ b/core/modules/tour/tests/src/Functional/Rest/TourJsonAnonTest.php
@@ -21,4 +21,9 @@ class TourJsonAnonTest extends TourResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/tour/tests/src/Functional/Rest/TourJsonBasicAuthTest.php b/core/modules/tour/tests/src/Functional/Rest/TourJsonBasicAuthTest.php
index fb1ff6995c4b..bad2b4112b1d 100644
--- a/core/modules/tour/tests/src/Functional/Rest/TourJsonBasicAuthTest.php
+++ b/core/modules/tour/tests/src/Functional/Rest/TourJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class TourJsonBasicAuthTest extends TourResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/tour/tests/src/Functional/Rest/TourJsonCookieTest.php b/core/modules/tour/tests/src/Functional/Rest/TourJsonCookieTest.php
index c173395b3a6a..f124c5ce331a 100644
--- a/core/modules/tour/tests/src/Functional/Rest/TourJsonCookieTest.php
+++ b/core/modules/tour/tests/src/Functional/Rest/TourJsonCookieTest.php
@@ -26,4 +26,9 @@ class TourJsonCookieTest extends TourResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/tour/tests/src/Functional/Rest/TourXmlAnonTest.php b/core/modules/tour/tests/src/Functional/Rest/TourXmlAnonTest.php
index 8f44c87bbdd3..416c3b353b41 100644
--- a/core/modules/tour/tests/src/Functional/Rest/TourXmlAnonTest.php
+++ b/core/modules/tour/tests/src/Functional/Rest/TourXmlAnonTest.php
@@ -23,4 +23,9 @@ class TourXmlAnonTest extends TourResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/tour/tests/src/Functional/Rest/TourXmlBasicAuthTest.php b/core/modules/tour/tests/src/Functional/Rest/TourXmlBasicAuthTest.php
index 618b41defdd7..fca59e3ae901 100644
--- a/core/modules/tour/tests/src/Functional/Rest/TourXmlBasicAuthTest.php
+++ b/core/modules/tour/tests/src/Functional/Rest/TourXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class TourXmlBasicAuthTest extends TourResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/tour/tests/src/Functional/Rest/TourXmlCookieTest.php b/core/modules/tour/tests/src/Functional/Rest/TourXmlCookieTest.php
index 4d65bfff3db2..4fee143b932a 100644
--- a/core/modules/tour/tests/src/Functional/Rest/TourXmlCookieTest.php
+++ b/core/modules/tour/tests/src/Functional/Rest/TourXmlCookieTest.php
@@ -28,4 +28,9 @@ class TourXmlCookieTest extends TourResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/tour/tests/src/Functional/TourCacheTagsTest.php b/core/modules/tour/tests/src/Functional/TourCacheTagsTest.php
index daed6fa292b3..d85e9a56b2a3 100644
--- a/core/modules/tour/tests/src/Functional/TourCacheTagsTest.php
+++ b/core/modules/tour/tests/src/Functional/TourCacheTagsTest.php
@@ -20,6 +20,11 @@ class TourCacheTagsTest extends PageCacheTagsTestBase {
    */
   public static $modules = ['tour', 'tour_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/tour/tests/src/Functional/TourHelpPageTest.php b/core/modules/tour/tests/src/Functional/TourHelpPageTest.php
index ad60df104f20..a88da72cb9aa 100644
--- a/core/modules/tour/tests/src/Functional/TourHelpPageTest.php
+++ b/core/modules/tour/tests/src/Functional/TourHelpPageTest.php
@@ -18,6 +18,11 @@ class TourHelpPageTest extends BrowserTestBase {
    */
   public static $modules = ['help', 'tour', 'locale', 'language'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * User that can access tours and help.
    *
diff --git a/core/modules/tour/tests/src/Functional/TourTest.php b/core/modules/tour/tests/src/Functional/TourTest.php
index b20b1b8779ec..cba8ff2801e2 100644
--- a/core/modules/tour/tests/src/Functional/TourTest.php
+++ b/core/modules/tour/tests/src/Functional/TourTest.php
@@ -20,6 +20,11 @@ class TourTest extends TourTestBasic {
    */
   public static $modules = ['block', 'tour', 'locale', 'language', 'tour_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The permissions required for a logged in user to test tour tips.
    *
diff --git a/core/modules/tracker/tests/src/Functional/TrackerNodeAccessTest.php b/core/modules/tracker/tests/src/Functional/TrackerNodeAccessTest.php
index 2b320ae4b6df..990612d0beb8 100644
--- a/core/modules/tracker/tests/src/Functional/TrackerNodeAccessTest.php
+++ b/core/modules/tracker/tests/src/Functional/TrackerNodeAccessTest.php
@@ -23,6 +23,11 @@ class TrackerNodeAccessTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'comment', 'tracker', 'node_access_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     node_access_rebuild();
diff --git a/core/modules/tracker/tests/src/Functional/TrackerTest.php b/core/modules/tracker/tests/src/Functional/TrackerTest.php
index 63d1cb2f426d..3d907212c893 100644
--- a/core/modules/tracker/tests/src/Functional/TrackerTest.php
+++ b/core/modules/tracker/tests/src/Functional/TrackerTest.php
@@ -31,6 +31,11 @@ class TrackerTest extends BrowserTestBase {
    */
   public static $modules = ['block', 'comment', 'tracker', 'history', 'node_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The main user for testing.
    *
diff --git a/core/modules/update/tests/src/Functional/FileTransferAuthorizeFormTest.php b/core/modules/update/tests/src/Functional/FileTransferAuthorizeFormTest.php
index d768b06d8183..f2c82a0bb2ce 100644
--- a/core/modules/update/tests/src/Functional/FileTransferAuthorizeFormTest.php
+++ b/core/modules/update/tests/src/Functional/FileTransferAuthorizeFormTest.php
@@ -16,6 +16,11 @@ class FileTransferAuthorizeFormTest extends UpdateTestBase {
    */
   public static $modules = ['update', 'update_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     $admin_user = $this->drupalCreateUser(['administer modules', 'administer software updates', 'administer site configuration']);
diff --git a/core/modules/update/tests/src/Functional/UpdateContribTest.php b/core/modules/update/tests/src/Functional/UpdateContribTest.php
index 5db38ce3457b..feabdcfd8bbd 100644
--- a/core/modules/update/tests/src/Functional/UpdateContribTest.php
+++ b/core/modules/update/tests/src/Functional/UpdateContribTest.php
@@ -21,6 +21,11 @@ class UpdateContribTest extends UpdateTestBase {
    */
   public static $modules = ['update_test', 'update', 'aaa_update_test', 'bbb_update_test', 'ccc_update_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     $admin_user = $this->drupalCreateUser(['administer site configuration']);
diff --git a/core/modules/update/tests/src/Functional/UpdateCoreTest.php b/core/modules/update/tests/src/Functional/UpdateCoreTest.php
index dec4022615ab..d0b0b9330197 100644
--- a/core/modules/update/tests/src/Functional/UpdateCoreTest.php
+++ b/core/modules/update/tests/src/Functional/UpdateCoreTest.php
@@ -23,6 +23,11 @@ class UpdateCoreTest extends UpdateTestBase {
    */
   public static $modules = ['update_test', 'update', 'language', 'block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     $admin_user = $this->drupalCreateUser(['administer site configuration', 'administer modules', 'administer themes']);
diff --git a/core/modules/update/tests/src/Functional/UpdateUploadTest.php b/core/modules/update/tests/src/Functional/UpdateUploadTest.php
index 74cfc5770ba0..a05e8a35a3b0 100644
--- a/core/modules/update/tests/src/Functional/UpdateUploadTest.php
+++ b/core/modules/update/tests/src/Functional/UpdateUploadTest.php
@@ -25,6 +25,11 @@ class UpdateUploadTest extends UpdateTestBase {
    */
   public static $modules = ['update', 'update_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     $admin_user = $this->drupalCreateUser(['administer modules', 'administer software updates', 'administer site configuration']);
diff --git a/core/modules/user/tests/src/Functional/AccessRoleUITest.php b/core/modules/user/tests/src/Functional/AccessRoleUITest.php
index d5346b1237eb..64615562b0da 100644
--- a/core/modules/user/tests/src/Functional/AccessRoleUITest.php
+++ b/core/modules/user/tests/src/Functional/AccessRoleUITest.php
@@ -27,6 +27,11 @@ class AccessRoleUITest extends UITestBase {
    */
   public static $modules = ['user', 'user_test_views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/user/tests/src/Functional/Hal/RoleHalJsonAnonTest.php b/core/modules/user/tests/src/Functional/Hal/RoleHalJsonAnonTest.php
index a08a1d094a89..fa60f6e6a168 100644
--- a/core/modules/user/tests/src/Functional/Hal/RoleHalJsonAnonTest.php
+++ b/core/modules/user/tests/src/Functional/Hal/RoleHalJsonAnonTest.php
@@ -17,6 +17,11 @@ class RoleHalJsonAnonTest extends RoleResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/user/tests/src/Functional/Hal/RoleHalJsonBasicAuthTest.php b/core/modules/user/tests/src/Functional/Hal/RoleHalJsonBasicAuthTest.php
index 1e613e5d73fc..5e270312080e 100644
--- a/core/modules/user/tests/src/Functional/Hal/RoleHalJsonBasicAuthTest.php
+++ b/core/modules/user/tests/src/Functional/Hal/RoleHalJsonBasicAuthTest.php
@@ -17,6 +17,11 @@ class RoleHalJsonBasicAuthTest extends RoleResourceTestBase {
    */
   public static $modules = ['hal', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/user/tests/src/Functional/Hal/RoleHalJsonCookieTest.php b/core/modules/user/tests/src/Functional/Hal/RoleHalJsonCookieTest.php
index 0074e0516cb1..deaccbdc9632 100644
--- a/core/modules/user/tests/src/Functional/Hal/RoleHalJsonCookieTest.php
+++ b/core/modules/user/tests/src/Functional/Hal/RoleHalJsonCookieTest.php
@@ -17,6 +17,11 @@ class RoleHalJsonCookieTest extends RoleResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/user/tests/src/Functional/Hal/UserHalJsonAnonTest.php b/core/modules/user/tests/src/Functional/Hal/UserHalJsonAnonTest.php
index b33c6868bcbe..18baea1d0b28 100644
--- a/core/modules/user/tests/src/Functional/Hal/UserHalJsonAnonTest.php
+++ b/core/modules/user/tests/src/Functional/Hal/UserHalJsonAnonTest.php
@@ -19,6 +19,11 @@ class UserHalJsonAnonTest extends UserResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/user/tests/src/Functional/Hal/UserHalJsonBasicAuthTest.php b/core/modules/user/tests/src/Functional/Hal/UserHalJsonBasicAuthTest.php
index 7da859e06089..0d34b132ae70 100644
--- a/core/modules/user/tests/src/Functional/Hal/UserHalJsonBasicAuthTest.php
+++ b/core/modules/user/tests/src/Functional/Hal/UserHalJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class UserHalJsonBasicAuthTest extends UserHalJsonAnonTest {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/user/tests/src/Functional/Hal/UserHalJsonCookieTest.php b/core/modules/user/tests/src/Functional/Hal/UserHalJsonCookieTest.php
index e5e785cc80a6..2945db5a6ed7 100644
--- a/core/modules/user/tests/src/Functional/Hal/UserHalJsonCookieTest.php
+++ b/core/modules/user/tests/src/Functional/Hal/UserHalJsonCookieTest.php
@@ -16,4 +16,9 @@ class UserHalJsonCookieTest extends UserHalJsonAnonTest {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/user/tests/src/Functional/Rest/RoleJsonAnonTest.php b/core/modules/user/tests/src/Functional/Rest/RoleJsonAnonTest.php
index 16e3e03eea60..7cf62c707b64 100644
--- a/core/modules/user/tests/src/Functional/Rest/RoleJsonAnonTest.php
+++ b/core/modules/user/tests/src/Functional/Rest/RoleJsonAnonTest.php
@@ -21,4 +21,9 @@ class RoleJsonAnonTest extends RoleResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/user/tests/src/Functional/Rest/RoleJsonBasicAuthTest.php b/core/modules/user/tests/src/Functional/Rest/RoleJsonBasicAuthTest.php
index 79d16cb90b76..39993113cd01 100644
--- a/core/modules/user/tests/src/Functional/Rest/RoleJsonBasicAuthTest.php
+++ b/core/modules/user/tests/src/Functional/Rest/RoleJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class RoleJsonBasicAuthTest extends RoleResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/user/tests/src/Functional/Rest/RoleJsonCookieTest.php b/core/modules/user/tests/src/Functional/Rest/RoleJsonCookieTest.php
index 6c31ab004140..03f517fa4c18 100644
--- a/core/modules/user/tests/src/Functional/Rest/RoleJsonCookieTest.php
+++ b/core/modules/user/tests/src/Functional/Rest/RoleJsonCookieTest.php
@@ -26,4 +26,9 @@ class RoleJsonCookieTest extends RoleResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/user/tests/src/Functional/Rest/RoleXmlAnonTest.php b/core/modules/user/tests/src/Functional/Rest/RoleXmlAnonTest.php
index 14910a62026d..a3e2e0a5b5f0 100644
--- a/core/modules/user/tests/src/Functional/Rest/RoleXmlAnonTest.php
+++ b/core/modules/user/tests/src/Functional/Rest/RoleXmlAnonTest.php
@@ -23,4 +23,9 @@ class RoleXmlAnonTest extends RoleResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/user/tests/src/Functional/Rest/RoleXmlBasicAuthTest.php b/core/modules/user/tests/src/Functional/Rest/RoleXmlBasicAuthTest.php
index fa98edd47c01..4fda554c2483 100644
--- a/core/modules/user/tests/src/Functional/Rest/RoleXmlBasicAuthTest.php
+++ b/core/modules/user/tests/src/Functional/Rest/RoleXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class RoleXmlBasicAuthTest extends RoleResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/user/tests/src/Functional/Rest/RoleXmlCookieTest.php b/core/modules/user/tests/src/Functional/Rest/RoleXmlCookieTest.php
index 5e04d7c35064..8767934394a5 100644
--- a/core/modules/user/tests/src/Functional/Rest/RoleXmlCookieTest.php
+++ b/core/modules/user/tests/src/Functional/Rest/RoleXmlCookieTest.php
@@ -28,4 +28,9 @@ class RoleXmlCookieTest extends RoleResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/user/tests/src/Functional/Rest/UserJsonAnonTest.php b/core/modules/user/tests/src/Functional/Rest/UserJsonAnonTest.php
index 5b7e09e2e350..ba2b0b392d8e 100644
--- a/core/modules/user/tests/src/Functional/Rest/UserJsonAnonTest.php
+++ b/core/modules/user/tests/src/Functional/Rest/UserJsonAnonTest.php
@@ -21,4 +21,9 @@ class UserJsonAnonTest extends UserResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/user/tests/src/Functional/Rest/UserJsonBasicAuthTest.php b/core/modules/user/tests/src/Functional/Rest/UserJsonBasicAuthTest.php
index 7a1ea2674e5f..15ba10bc7764 100644
--- a/core/modules/user/tests/src/Functional/Rest/UserJsonBasicAuthTest.php
+++ b/core/modules/user/tests/src/Functional/Rest/UserJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class UserJsonBasicAuthTest extends UserResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/user/tests/src/Functional/Rest/UserJsonCookieTest.php b/core/modules/user/tests/src/Functional/Rest/UserJsonCookieTest.php
index 6e325d8b2ba7..21a46cd06fd9 100644
--- a/core/modules/user/tests/src/Functional/Rest/UserJsonCookieTest.php
+++ b/core/modules/user/tests/src/Functional/Rest/UserJsonCookieTest.php
@@ -26,4 +26,9 @@ class UserJsonCookieTest extends UserResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/user/tests/src/Functional/Rest/UserXmlAnonTest.php b/core/modules/user/tests/src/Functional/Rest/UserXmlAnonTest.php
index 4629192ce0a1..3340729364ae 100644
--- a/core/modules/user/tests/src/Functional/Rest/UserXmlAnonTest.php
+++ b/core/modules/user/tests/src/Functional/Rest/UserXmlAnonTest.php
@@ -23,6 +23,11 @@ class UserXmlAnonTest extends UserResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/user/tests/src/Functional/Rest/UserXmlBasicAuthTest.php b/core/modules/user/tests/src/Functional/Rest/UserXmlBasicAuthTest.php
index fc985980c3f4..f213e1b5d006 100644
--- a/core/modules/user/tests/src/Functional/Rest/UserXmlBasicAuthTest.php
+++ b/core/modules/user/tests/src/Functional/Rest/UserXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class UserXmlBasicAuthTest extends UserResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/user/tests/src/Functional/Rest/UserXmlCookieTest.php b/core/modules/user/tests/src/Functional/Rest/UserXmlCookieTest.php
index 9a0c724f4d76..6015e2df5530 100644
--- a/core/modules/user/tests/src/Functional/Rest/UserXmlCookieTest.php
+++ b/core/modules/user/tests/src/Functional/Rest/UserXmlCookieTest.php
@@ -28,6 +28,11 @@ class UserXmlCookieTest extends UserResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/user/tests/src/Functional/RestRegisterUserTest.php b/core/modules/user/tests/src/Functional/RestRegisterUserTest.php
index 5f06214e03f5..990892a6f3a8 100644
--- a/core/modules/user/tests/src/Functional/RestRegisterUserTest.php
+++ b/core/modules/user/tests/src/Functional/RestRegisterUserTest.php
@@ -22,6 +22,11 @@ class RestRegisterUserTest extends ResourceTestBase {
     getMails as drupalGetMails;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/user/tests/src/Functional/UserAccountLinksTest.php b/core/modules/user/tests/src/Functional/UserAccountLinksTest.php
index c09fc34daffc..691695a0904b 100644
--- a/core/modules/user/tests/src/Functional/UserAccountLinksTest.php
+++ b/core/modules/user/tests/src/Functional/UserAccountLinksTest.php
@@ -18,6 +18,11 @@ class UserAccountLinksTest extends BrowserTestBase {
    */
   public static $modules = ['menu_ui', 'block', 'test_page_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/user/tests/src/Functional/UserAdminLanguageTest.php b/core/modules/user/tests/src/Functional/UserAdminLanguageTest.php
index 5e9f3ee46506..4d5ef5b60282 100644
--- a/core/modules/user/tests/src/Functional/UserAdminLanguageTest.php
+++ b/core/modules/user/tests/src/Functional/UserAdminLanguageTest.php
@@ -33,6 +33,11 @@ class UserAdminLanguageTest extends BrowserTestBase {
    */
   public static $modules = ['user', 'language', 'language_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
     // User to add and remove language.
diff --git a/core/modules/user/tests/src/Functional/UserAdminListingTest.php b/core/modules/user/tests/src/Functional/UserAdminListingTest.php
index 1617d14eb4e4..ec4375a143be 100644
--- a/core/modules/user/tests/src/Functional/UserAdminListingTest.php
+++ b/core/modules/user/tests/src/Functional/UserAdminListingTest.php
@@ -13,6 +13,11 @@
  */
 class UserAdminListingTest extends BrowserTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Tests the listing.
    */
diff --git a/core/modules/user/tests/src/Functional/UserAdminTest.php b/core/modules/user/tests/src/Functional/UserAdminTest.php
index 298d41493eaf..991f99304d69 100644
--- a/core/modules/user/tests/src/Functional/UserAdminTest.php
+++ b/core/modules/user/tests/src/Functional/UserAdminTest.php
@@ -25,6 +25,11 @@ class UserAdminTest extends BrowserTestBase {
    */
   public static $modules = ['taxonomy', 'views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Registers a user and deletes it.
    */
diff --git a/core/modules/user/tests/src/Functional/UserBlocksTest.php b/core/modules/user/tests/src/Functional/UserBlocksTest.php
index f308283dee90..0f9b82b8fb68 100644
--- a/core/modules/user/tests/src/Functional/UserBlocksTest.php
+++ b/core/modules/user/tests/src/Functional/UserBlocksTest.php
@@ -21,6 +21,11 @@ class UserBlocksTest extends BrowserTestBase {
    */
   public static $modules = ['block', 'views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * A user with the 'administer blocks' permission.
    *
diff --git a/core/modules/user/tests/src/Functional/UserCacheTagsTest.php b/core/modules/user/tests/src/Functional/UserCacheTagsTest.php
index c9ab91fac71a..a65b34db7e73 100644
--- a/core/modules/user/tests/src/Functional/UserCacheTagsTest.php
+++ b/core/modules/user/tests/src/Functional/UserCacheTagsTest.php
@@ -19,6 +19,11 @@ class UserCacheTagsTest extends EntityWithUriCacheTagsTestBase {
    */
   public static $modules = ['user'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/user/tests/src/Functional/UserCancelTest.php b/core/modules/user/tests/src/Functional/UserCancelTest.php
index 365be54f48c9..65632c03a0bf 100644
--- a/core/modules/user/tests/src/Functional/UserCancelTest.php
+++ b/core/modules/user/tests/src/Functional/UserCancelTest.php
@@ -24,6 +24,11 @@ class UserCancelTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'comment'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/user/tests/src/Functional/UserCreateFailMailTest.php b/core/modules/user/tests/src/Functional/UserCreateFailMailTest.php
index 38f2514a496f..96323279a314 100644
--- a/core/modules/user/tests/src/Functional/UserCreateFailMailTest.php
+++ b/core/modules/user/tests/src/Functional/UserCreateFailMailTest.php
@@ -18,6 +18,11 @@ class UserCreateFailMailTest extends BrowserTestBase {
    */
   public static $modules = ['system_mail_failure_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the create user administration page.
    */
diff --git a/core/modules/user/tests/src/Functional/UserCreateTest.php b/core/modules/user/tests/src/Functional/UserCreateTest.php
index 8c281111459d..fceb1af1d66a 100644
--- a/core/modules/user/tests/src/Functional/UserCreateTest.php
+++ b/core/modules/user/tests/src/Functional/UserCreateTest.php
@@ -25,6 +25,11 @@ class UserCreateTest extends BrowserTestBase {
    */
   public static $modules = ['image'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Create a user through the administration interface and ensure that it
    * displays in the user list.
diff --git a/core/modules/user/tests/src/Functional/UserEditTest.php b/core/modules/user/tests/src/Functional/UserEditTest.php
index eba49bab596d..6a71927a96cc 100644
--- a/core/modules/user/tests/src/Functional/UserEditTest.php
+++ b/core/modules/user/tests/src/Functional/UserEditTest.php
@@ -12,6 +12,11 @@
  */
 class UserEditTest extends BrowserTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test user edit page.
    */
diff --git a/core/modules/user/tests/src/Functional/UserEditedOwnAccountTest.php b/core/modules/user/tests/src/Functional/UserEditedOwnAccountTest.php
index 75f654297b8d..4fe8d0a6baa2 100644
--- a/core/modules/user/tests/src/Functional/UserEditedOwnAccountTest.php
+++ b/core/modules/user/tests/src/Functional/UserEditedOwnAccountTest.php
@@ -12,6 +12,11 @@
  */
 class UserEditedOwnAccountTest extends BrowserTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   public function testUserEditedOwnAccount() {
     // Change account setting 'Who can register accounts?' to Administrators
     // only.
diff --git a/core/modules/user/tests/src/Functional/UserLanguageCreationTest.php b/core/modules/user/tests/src/Functional/UserLanguageCreationTest.php
index 6f493418b208..85e39589db7d 100644
--- a/core/modules/user/tests/src/Functional/UserLanguageCreationTest.php
+++ b/core/modules/user/tests/src/Functional/UserLanguageCreationTest.php
@@ -20,6 +20,11 @@ class UserLanguageCreationTest extends BrowserTestBase {
    */
   public static $modules = ['user', 'language'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Functional test for language handling during user creation.
    */
diff --git a/core/modules/user/tests/src/Functional/UserLanguageTest.php b/core/modules/user/tests/src/Functional/UserLanguageTest.php
index 0e6c0f1a75db..d221a61c1eb6 100644
--- a/core/modules/user/tests/src/Functional/UserLanguageTest.php
+++ b/core/modules/user/tests/src/Functional/UserLanguageTest.php
@@ -19,6 +19,11 @@ class UserLanguageTest extends BrowserTestBase {
    */
   public static $modules = ['user', 'language'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test if user can change their default language.
    */
diff --git a/core/modules/user/tests/src/Functional/UserLoginHttpTest.php b/core/modules/user/tests/src/Functional/UserLoginHttpTest.php
index 47287810e01c..0402f6280646 100644
--- a/core/modules/user/tests/src/Functional/UserLoginHttpTest.php
+++ b/core/modules/user/tests/src/Functional/UserLoginHttpTest.php
@@ -32,6 +32,11 @@ class UserLoginHttpTest extends BrowserTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The cookie jar.
    *
diff --git a/core/modules/user/tests/src/Functional/UserLoginTest.php b/core/modules/user/tests/src/Functional/UserLoginTest.php
index e9c88b106f65..e067915867e9 100644
--- a/core/modules/user/tests/src/Functional/UserLoginTest.php
+++ b/core/modules/user/tests/src/Functional/UserLoginTest.php
@@ -13,6 +13,11 @@
  */
 class UserLoginTest extends BrowserTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests login with destination.
    */
diff --git a/core/modules/user/tests/src/Functional/UserPasswordResetTest.php b/core/modules/user/tests/src/Functional/UserPasswordResetTest.php
index 1bcbd1d1416d..650c2dfd01a5 100644
--- a/core/modules/user/tests/src/Functional/UserPasswordResetTest.php
+++ b/core/modules/user/tests/src/Functional/UserPasswordResetTest.php
@@ -34,6 +34,11 @@ class UserPasswordResetTest extends PageCacheTagsTestBase {
    */
   public static $modules = ['block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/user/tests/src/Functional/UserPermissionsTest.php b/core/modules/user/tests/src/Functional/UserPermissionsTest.php
index 14b0ca854e6a..0eb453fc2678 100644
--- a/core/modules/user/tests/src/Functional/UserPermissionsTest.php
+++ b/core/modules/user/tests/src/Functional/UserPermissionsTest.php
@@ -28,6 +28,11 @@ class UserPermissionsTest extends BrowserTestBase {
    */
   protected $rid;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp() {
     parent::setUp();
 
diff --git a/core/modules/user/tests/src/Functional/UserPictureTest.php b/core/modules/user/tests/src/Functional/UserPictureTest.php
index 3e853d70f9ec..efb785d6259c 100644
--- a/core/modules/user/tests/src/Functional/UserPictureTest.php
+++ b/core/modules/user/tests/src/Functional/UserPictureTest.php
@@ -30,6 +30,11 @@ class UserPictureTest extends BrowserTestBase {
    */
   protected $profile = 'standard';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * A regular user.
    *
diff --git a/core/modules/user/tests/src/Functional/UserRegistrationTest.php b/core/modules/user/tests/src/Functional/UserRegistrationTest.php
index 766baf304c2a..b72d7ec776fe 100644
--- a/core/modules/user/tests/src/Functional/UserRegistrationTest.php
+++ b/core/modules/user/tests/src/Functional/UserRegistrationTest.php
@@ -24,6 +24,11 @@ class UserRegistrationTest extends BrowserTestBase {
    */
   public static $modules = ['field_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   public function testRegistrationWithEmailVerification() {
     $config = $this->config('user.settings');
     // Require email verification.
diff --git a/core/modules/user/tests/src/Functional/UserRoleAdminTest.php b/core/modules/user/tests/src/Functional/UserRoleAdminTest.php
index c7e52135d695..ff529f83febf 100644
--- a/core/modules/user/tests/src/Functional/UserRoleAdminTest.php
+++ b/core/modules/user/tests/src/Functional/UserRoleAdminTest.php
@@ -27,6 +27,11 @@ class UserRoleAdminTest extends BrowserTestBase {
    */
   public static $modules = ['block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/user/tests/src/Functional/UserRolesAssignmentTest.php b/core/modules/user/tests/src/Functional/UserRolesAssignmentTest.php
index 6cd80562c540..4a417494fc2d 100644
--- a/core/modules/user/tests/src/Functional/UserRolesAssignmentTest.php
+++ b/core/modules/user/tests/src/Functional/UserRolesAssignmentTest.php
@@ -17,6 +17,11 @@ protected function setUp() {
     $this->drupalLogin($admin_user);
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that a user can be assigned a role and that the role can be removed
    * again.
diff --git a/core/modules/user/tests/src/Functional/UserSearchTest.php b/core/modules/user/tests/src/Functional/UserSearchTest.php
index 24ab0afef558..49fca33902e5 100644
--- a/core/modules/user/tests/src/Functional/UserSearchTest.php
+++ b/core/modules/user/tests/src/Functional/UserSearchTest.php
@@ -19,6 +19,11 @@ class UserSearchTest extends BrowserTestBase {
    */
   public static $modules = ['search'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   public function testUserSearch() {
     // Verify that a user without 'administer users' permission cannot search
     // for users by email address. Additionally, ensure that the username has a
diff --git a/core/modules/user/tests/src/Functional/UserSubAdminTest.php b/core/modules/user/tests/src/Functional/UserSubAdminTest.php
index 029df0301acd..0de619f2410b 100644
--- a/core/modules/user/tests/src/Functional/UserSubAdminTest.php
+++ b/core/modules/user/tests/src/Functional/UserSubAdminTest.php
@@ -16,6 +16,11 @@ class UserSubAdminTest extends BrowserTestBase {
    */
   public static $modules = ['user_access_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test create and cancel forms as 'sub-admin'.
    */
diff --git a/core/modules/user/tests/src/Functional/UserTimeZoneTest.php b/core/modules/user/tests/src/Functional/UserTimeZoneTest.php
index ccf43253def6..914fffa1c9aa 100644
--- a/core/modules/user/tests/src/Functional/UserTimeZoneTest.php
+++ b/core/modules/user/tests/src/Functional/UserTimeZoneTest.php
@@ -19,6 +19,11 @@ class UserTimeZoneTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'system_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the display of dates and time when user-configurable time zones are set.
    */
diff --git a/core/modules/user/tests/src/Functional/UserTokenReplaceTest.php b/core/modules/user/tests/src/Functional/UserTokenReplaceTest.php
index 7ff6b31b8ea3..1bc36a61510f 100644
--- a/core/modules/user/tests/src/Functional/UserTokenReplaceTest.php
+++ b/core/modules/user/tests/src/Functional/UserTokenReplaceTest.php
@@ -24,6 +24,11 @@ class UserTokenReplaceTest extends BrowserTestBase {
    */
   public static $modules = ['language', 'user_hooks_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/user/tests/src/Functional/UserTranslationUITest.php b/core/modules/user/tests/src/Functional/UserTranslationUITest.php
index d087d528d719..811a2f174428 100644
--- a/core/modules/user/tests/src/Functional/UserTranslationUITest.php
+++ b/core/modules/user/tests/src/Functional/UserTranslationUITest.php
@@ -25,6 +25,11 @@ class UserTranslationUITest extends ContentTranslationUITestBase {
    */
   public static $modules = ['language', 'content_translation', 'user', 'views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   protected function setUp() {
     $this->entityTypeId = 'user';
     $this->testLanguageSelector = FALSE;
diff --git a/core/modules/user/tests/src/Functional/Views/AccessRoleTest.php b/core/modules/user/tests/src/Functional/Views/AccessRoleTest.php
index 62bcd6c0f7ce..4093fa45587d 100644
--- a/core/modules/user/tests/src/Functional/Views/AccessRoleTest.php
+++ b/core/modules/user/tests/src/Functional/Views/AccessRoleTest.php
@@ -25,6 +25,11 @@ class AccessRoleTest extends AccessTestBase {
    */
   public static $testViews = ['test_access_role'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests role access plugin.
    */
diff --git a/core/modules/user/tests/src/Functional/Views/BulkFormAccessTest.php b/core/modules/user/tests/src/Functional/Views/BulkFormAccessTest.php
index 5f613f3b1684..358ae1379137 100644
--- a/core/modules/user/tests/src/Functional/Views/BulkFormAccessTest.php
+++ b/core/modules/user/tests/src/Functional/Views/BulkFormAccessTest.php
@@ -21,6 +21,11 @@ class BulkFormAccessTest extends UserTestBase {
    */
   public static $modules = ['user_access_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/user/tests/src/Functional/Views/BulkFormTest.php b/core/modules/user/tests/src/Functional/Views/BulkFormTest.php
index a9ba63feed6b..f7cb4f3fe043 100644
--- a/core/modules/user/tests/src/Functional/Views/BulkFormTest.php
+++ b/core/modules/user/tests/src/Functional/Views/BulkFormTest.php
@@ -21,6 +21,11 @@ class BulkFormTest extends UserTestBase {
    */
   public static $modules = ['views_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/user/tests/src/Functional/Views/FilterPermissionUiTest.php b/core/modules/user/tests/src/Functional/Views/FilterPermissionUiTest.php
index d08c2f31695f..18358585835b 100644
--- a/core/modules/user/tests/src/Functional/Views/FilterPermissionUiTest.php
+++ b/core/modules/user/tests/src/Functional/Views/FilterPermissionUiTest.php
@@ -27,6 +27,11 @@ class FilterPermissionUiTest extends ViewTestBase {
    */
   public static $modules = ['user', 'user_test_views', 'views_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp($import_test_views = TRUE) {
     parent::setUp($import_test_views);
 
diff --git a/core/modules/user/tests/src/Functional/Views/HandlerFieldRoleTest.php b/core/modules/user/tests/src/Functional/Views/HandlerFieldRoleTest.php
index 9c2430e11a3c..ca191b5a0277 100644
--- a/core/modules/user/tests/src/Functional/Views/HandlerFieldRoleTest.php
+++ b/core/modules/user/tests/src/Functional/Views/HandlerFieldRoleTest.php
@@ -20,6 +20,11 @@ class HandlerFieldRoleTest extends UserTestBase {
    */
   public static $testViews = ['test_views_handler_field_role'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   public function testRole() {
     // Create a couple of roles for the view.
     $rolename_a = 'a' . $this->randomMachineName(8);
diff --git a/core/modules/user/tests/src/Functional/Views/HandlerFieldUserNameTest.php b/core/modules/user/tests/src/Functional/Views/HandlerFieldUserNameTest.php
index 0525e3d1fe05..108121e61d9e 100644
--- a/core/modules/user/tests/src/Functional/Views/HandlerFieldUserNameTest.php
+++ b/core/modules/user/tests/src/Functional/Views/HandlerFieldUserNameTest.php
@@ -20,6 +20,11 @@ class HandlerFieldUserNameTest extends UserTestBase {
    */
   public static $testViews = ['test_views_handler_field_user_name'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   public function testUserName() {
     /** @var \Drupal\Core\Render\RendererInterface $renderer */
     $renderer = \Drupal::service('renderer');
diff --git a/core/modules/user/tests/src/Functional/Views/HandlerFilterUserNameTest.php b/core/modules/user/tests/src/Functional/Views/HandlerFilterUserNameTest.php
index a5d271092a02..dbb8fc56c436 100644
--- a/core/modules/user/tests/src/Functional/Views/HandlerFilterUserNameTest.php
+++ b/core/modules/user/tests/src/Functional/Views/HandlerFilterUserNameTest.php
@@ -21,6 +21,11 @@ class HandlerFilterUserNameTest extends ViewTestBase {
    */
   public static $modules = ['views_ui', 'user_test_views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/user/tests/src/Functional/Views/RolesRidArgumentTest.php b/core/modules/user/tests/src/Functional/Views/RolesRidArgumentTest.php
index fd36ec49bd57..50c24f5afb6f 100644
--- a/core/modules/user/tests/src/Functional/Views/RolesRidArgumentTest.php
+++ b/core/modules/user/tests/src/Functional/Views/RolesRidArgumentTest.php
@@ -17,6 +17,11 @@ class RolesRidArgumentTest extends UserTestBase {
    */
   public static $testViews = ['test_user_roles_rid'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the generated title of a user: roles argument.
    */
diff --git a/core/modules/user/tests/src/Functional/Views/UserChangedTest.php b/core/modules/user/tests/src/Functional/Views/UserChangedTest.php
index 2271c0ce0726..d22d2b4710f7 100644
--- a/core/modules/user/tests/src/Functional/Views/UserChangedTest.php
+++ b/core/modules/user/tests/src/Functional/Views/UserChangedTest.php
@@ -19,6 +19,11 @@ class UserChangedTest extends ViewTestBase {
    */
   public static $modules = ['views_ui', 'user_test_views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/user/tests/src/Functional/Views/UserFieldsAccessChangeTest.php b/core/modules/user/tests/src/Functional/Views/UserFieldsAccessChangeTest.php
index 7f75cf3aadb9..ca3e8e9cccbb 100644
--- a/core/modules/user/tests/src/Functional/Views/UserFieldsAccessChangeTest.php
+++ b/core/modules/user/tests/src/Functional/Views/UserFieldsAccessChangeTest.php
@@ -16,6 +16,11 @@ class UserFieldsAccessChangeTest extends UserTestBase {
    */
   public static $modules = ['user_access_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/user/tests/src/FunctionalJavascript/RegistrationWithUserFieldsTest.php b/core/modules/user/tests/src/FunctionalJavascript/RegistrationWithUserFieldsTest.php
index 9f80094c0945..d62bae8193e6 100644
--- a/core/modules/user/tests/src/FunctionalJavascript/RegistrationWithUserFieldsTest.php
+++ b/core/modules/user/tests/src/FunctionalJavascript/RegistrationWithUserFieldsTest.php
@@ -33,6 +33,11 @@ class RegistrationWithUserFieldsTest extends WebDriverTestBase {
    */
   public static $modules = ['field_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/views/tests/src/Functional/BulkFormTest.php b/core/modules/views/tests/src/Functional/BulkFormTest.php
index 73862992be21..033902438e74 100644
--- a/core/modules/views/tests/src/Functional/BulkFormTest.php
+++ b/core/modules/views/tests/src/Functional/BulkFormTest.php
@@ -21,6 +21,11 @@ class BulkFormTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'action_bulk_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the bulk form.
    */
diff --git a/core/modules/views/tests/src/Functional/DefaultViewsTest.php b/core/modules/views/tests/src/Functional/DefaultViewsTest.php
index 1e1cbee2a4e9..071786a47072 100644
--- a/core/modules/views/tests/src/Functional/DefaultViewsTest.php
+++ b/core/modules/views/tests/src/Functional/DefaultViewsTest.php
@@ -32,6 +32,11 @@ class DefaultViewsTest extends ViewTestBase {
    */
   public static $modules = ['views', 'node', 'search', 'comment', 'taxonomy', 'block', 'user'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * An array of argument arrays to use for default views.
    *
diff --git a/core/modules/views/tests/src/Functional/Entity/BaseFieldAccessTest.php b/core/modules/views/tests/src/Functional/Entity/BaseFieldAccessTest.php
index 7a75c3cb2fd6..ae81caa8b2fd 100644
--- a/core/modules/views/tests/src/Functional/Entity/BaseFieldAccessTest.php
+++ b/core/modules/views/tests/src/Functional/Entity/BaseFieldAccessTest.php
@@ -29,6 +29,11 @@ class BaseFieldAccessTest extends ViewTestBase {
     'views', 'views_test_config', 'entity_test', 'node', 'views_entity_test',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/views/tests/src/Functional/Entity/EntityQueryAccessTest.php b/core/modules/views/tests/src/Functional/Entity/EntityQueryAccessTest.php
index 73a7f655109d..077e8c306349 100644
--- a/core/modules/views/tests/src/Functional/Entity/EntityQueryAccessTest.php
+++ b/core/modules/views/tests/src/Functional/Entity/EntityQueryAccessTest.php
@@ -25,6 +25,11 @@ class EntityQueryAccessTest extends ViewTestBase {
     'views_test_query_access',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that the 'media_access' query tag is respected by Views.
    */
diff --git a/core/modules/views/tests/src/Functional/Entity/FieldEntityTest.php b/core/modules/views/tests/src/Functional/Entity/FieldEntityTest.php
index 2393b6d26993..e88c06b277f0 100644
--- a/core/modules/views/tests/src/Functional/Entity/FieldEntityTest.php
+++ b/core/modules/views/tests/src/Functional/Entity/FieldEntityTest.php
@@ -33,6 +33,11 @@ class FieldEntityTest extends ViewTestBase {
    */
   public static $modules = ['node', 'comment'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/views/tests/src/Functional/Entity/FieldEntityTranslationTest.php b/core/modules/views/tests/src/Functional/Entity/FieldEntityTranslationTest.php
index 2a227c543373..6c82768153ee 100644
--- a/core/modules/views/tests/src/Functional/Entity/FieldEntityTranslationTest.php
+++ b/core/modules/views/tests/src/Functional/Entity/FieldEntityTranslationTest.php
@@ -21,6 +21,11 @@ class FieldEntityTranslationTest extends ViewTestBase {
    */
   public static $modules = ['language', 'locale', 'content_translation', 'node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/views/tests/src/Functional/Entity/FieldRenderedEntityTranslationTest.php b/core/modules/views/tests/src/Functional/Entity/FieldRenderedEntityTranslationTest.php
index 5f04bc9208d7..7d7b3d24547d 100644
--- a/core/modules/views/tests/src/Functional/Entity/FieldRenderedEntityTranslationTest.php
+++ b/core/modules/views/tests/src/Functional/Entity/FieldRenderedEntityTranslationTest.php
@@ -18,6 +18,11 @@ class FieldRenderedEntityTranslationTest extends ViewTestBase {
    */
   public static $modules = ['language', 'locale', 'content_translation', 'node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/views/tests/src/Functional/Entity/ViewNonTranslatableEntityTest.php b/core/modules/views/tests/src/Functional/Entity/ViewNonTranslatableEntityTest.php
index 911cd61e66a5..e8d9094f85a4 100644
--- a/core/modules/views/tests/src/Functional/Entity/ViewNonTranslatableEntityTest.php
+++ b/core/modules/views/tests/src/Functional/Entity/ViewNonTranslatableEntityTest.php
@@ -25,6 +25,11 @@ class ViewNonTranslatableEntityTest extends BrowserTestBase {
     'views_ui',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests displaying a view of non-translatable entities.
    */
diff --git a/core/modules/views/tests/src/Functional/GlossaryTest.php b/core/modules/views/tests/src/Functional/GlossaryTest.php
index ed247f1829bc..04cda6e32b07 100644
--- a/core/modules/views/tests/src/Functional/GlossaryTest.php
+++ b/core/modules/views/tests/src/Functional/GlossaryTest.php
@@ -23,6 +23,11 @@ class GlossaryTest extends ViewTestBase {
    */
   public static $modules = ['node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the default glossary view.
    */
diff --git a/core/modules/views/tests/src/Functional/Hal/ViewHalJsonAnonTest.php b/core/modules/views/tests/src/Functional/Hal/ViewHalJsonAnonTest.php
index 134b00f223bd..45e5d3acc0e2 100644
--- a/core/modules/views/tests/src/Functional/Hal/ViewHalJsonAnonTest.php
+++ b/core/modules/views/tests/src/Functional/Hal/ViewHalJsonAnonTest.php
@@ -17,6 +17,11 @@ class ViewHalJsonAnonTest extends ViewResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/views/tests/src/Functional/Hal/ViewHalJsonBasicAuthTest.php b/core/modules/views/tests/src/Functional/Hal/ViewHalJsonBasicAuthTest.php
index 87c39852cff5..9bedfb513565 100644
--- a/core/modules/views/tests/src/Functional/Hal/ViewHalJsonBasicAuthTest.php
+++ b/core/modules/views/tests/src/Functional/Hal/ViewHalJsonBasicAuthTest.php
@@ -17,6 +17,11 @@ class ViewHalJsonBasicAuthTest extends ViewResourceTestBase {
    */
   public static $modules = ['hal', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/views/tests/src/Functional/Hal/ViewHalJsonCookieTest.php b/core/modules/views/tests/src/Functional/Hal/ViewHalJsonCookieTest.php
index aa5aa4f6b7ad..da2ca72b7b79 100644
--- a/core/modules/views/tests/src/Functional/Hal/ViewHalJsonCookieTest.php
+++ b/core/modules/views/tests/src/Functional/Hal/ViewHalJsonCookieTest.php
@@ -17,6 +17,11 @@ class ViewHalJsonCookieTest extends ViewResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/views/tests/src/Functional/Handler/AreaHTTPStatusCodeTest.php b/core/modules/views/tests/src/Functional/Handler/AreaHTTPStatusCodeTest.php
index dc914ce219e6..d284f4719a06 100644
--- a/core/modules/views/tests/src/Functional/Handler/AreaHTTPStatusCodeTest.php
+++ b/core/modules/views/tests/src/Functional/Handler/AreaHTTPStatusCodeTest.php
@@ -27,6 +27,11 @@ class AreaHTTPStatusCodeTest extends ViewTestBase {
    */
   public static $modules = ['node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the area handler.
    */
diff --git a/core/modules/views/tests/src/Functional/Handler/AreaTest.php b/core/modules/views/tests/src/Functional/Handler/AreaTest.php
index 1827319bbd05..170147eab00b 100644
--- a/core/modules/views/tests/src/Functional/Handler/AreaTest.php
+++ b/core/modules/views/tests/src/Functional/Handler/AreaTest.php
@@ -29,6 +29,11 @@ class AreaTest extends ViewTestBase {
    */
   public static $modules = ['node', 'views_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp($import_test_views = TRUE) {
     parent::setUp($import_test_views);
 
diff --git a/core/modules/views/tests/src/Functional/Handler/AreaTitleWebTest.php b/core/modules/views/tests/src/Functional/Handler/AreaTitleWebTest.php
index 9e1fcfad233d..23ab8dc28ade 100644
--- a/core/modules/views/tests/src/Functional/Handler/AreaTitleWebTest.php
+++ b/core/modules/views/tests/src/Functional/Handler/AreaTitleWebTest.php
@@ -20,6 +20,11 @@ class AreaTitleWebTest extends ViewTestBase {
    */
   public static $testViews = ['test_area_title'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/views/tests/src/Functional/Handler/FieldDropButtonTest.php b/core/modules/views/tests/src/Functional/Handler/FieldDropButtonTest.php
index e0e380b0f8d6..7eae8284a671 100644
--- a/core/modules/views/tests/src/Functional/Handler/FieldDropButtonTest.php
+++ b/core/modules/views/tests/src/Functional/Handler/FieldDropButtonTest.php
@@ -26,6 +26,11 @@ class FieldDropButtonTest extends ViewTestBase {
    */
   public static $modules = ['node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/views/tests/src/Functional/Handler/FieldEntityLinkBaseTest.php b/core/modules/views/tests/src/Functional/Handler/FieldEntityLinkBaseTest.php
index bd3f3f65cf71..04794ecd9779 100644
--- a/core/modules/views/tests/src/Functional/Handler/FieldEntityLinkBaseTest.php
+++ b/core/modules/views/tests/src/Functional/Handler/FieldEntityLinkBaseTest.php
@@ -25,6 +25,11 @@ class FieldEntityLinkBaseTest extends ViewTestBase {
    */
   public static $modules = ['node', 'language'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/views/tests/src/Functional/Handler/FieldEntityOperationsTest.php b/core/modules/views/tests/src/Functional/Handler/FieldEntityOperationsTest.php
index c8f962dbe8ef..c6c5a0909df9 100644
--- a/core/modules/views/tests/src/Functional/Handler/FieldEntityOperationsTest.php
+++ b/core/modules/views/tests/src/Functional/Handler/FieldEntityOperationsTest.php
@@ -28,6 +28,11 @@ class FieldEntityOperationsTest extends ViewTestBase {
    */
   public static $modules = ['node', 'language', 'views_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp($import_test_views = TRUE) {
     parent::setUp($import_test_views);
 
diff --git a/core/modules/views/tests/src/Functional/Handler/FieldGroupRowsWebTest.php b/core/modules/views/tests/src/Functional/Handler/FieldGroupRowsWebTest.php
index 275960cb0d4a..aa4a5617b799 100644
--- a/core/modules/views/tests/src/Functional/Handler/FieldGroupRowsWebTest.php
+++ b/core/modules/views/tests/src/Functional/Handler/FieldGroupRowsWebTest.php
@@ -28,6 +28,11 @@ class FieldGroupRowsWebTest extends ViewTestBase {
    */
   public static $modules = ['node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The page node type.
    *
diff --git a/core/modules/views/tests/src/Functional/Handler/FieldWebTest.php b/core/modules/views/tests/src/Functional/Handler/FieldWebTest.php
index c4715ab61c6d..7b3e747a555d 100644
--- a/core/modules/views/tests/src/Functional/Handler/FieldWebTest.php
+++ b/core/modules/views/tests/src/Functional/Handler/FieldWebTest.php
@@ -33,6 +33,11 @@ class FieldWebTest extends ViewTestBase {
    */
   public static $modules = ['node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Maps between the key in the expected result and the query result.
    *
diff --git a/core/modules/views/tests/src/Functional/Handler/FilterDateTest.php b/core/modules/views/tests/src/Functional/Handler/FilterDateTest.php
index 90bddc5f7a7d..0ef10459b60f 100644
--- a/core/modules/views/tests/src/Functional/Handler/FilterDateTest.php
+++ b/core/modules/views/tests/src/Functional/Handler/FilterDateTest.php
@@ -31,6 +31,11 @@ class FilterDateTest extends ViewTestBase {
    */
   public static $modules = ['node', 'views_ui', 'datetime'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * The date formatter.
    *
diff --git a/core/modules/views/tests/src/Functional/Handler/FilterPlaceholderTextTest.php b/core/modules/views/tests/src/Functional/Handler/FilterPlaceholderTextTest.php
index 7d852f7c8700..4453acbac47a 100644
--- a/core/modules/views/tests/src/Functional/Handler/FilterPlaceholderTextTest.php
+++ b/core/modules/views/tests/src/Functional/Handler/FilterPlaceholderTextTest.php
@@ -23,6 +23,11 @@ class FilterPlaceholderTextTest extends ViewTestBase {
    */
   public static $modules = ['node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that HTML placeholders are added, when appropriate.
    */
diff --git a/core/modules/views/tests/src/Functional/Handler/HandlerAllTest.php b/core/modules/views/tests/src/Functional/Handler/HandlerAllTest.php
index e08f01d67543..e948273ec0b1 100644
--- a/core/modules/views/tests/src/Functional/Handler/HandlerAllTest.php
+++ b/core/modules/views/tests/src/Functional/Handler/HandlerAllTest.php
@@ -44,6 +44,11 @@ class HandlerAllTest extends ViewTestBase {
     'user',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests most of the handlers.
    */
diff --git a/core/modules/views/tests/src/Functional/Handler/HandlerTest.php b/core/modules/views/tests/src/Functional/Handler/HandlerTest.php
index cffe6d140262..08ee8f7cbf2e 100644
--- a/core/modules/views/tests/src/Functional/Handler/HandlerTest.php
+++ b/core/modules/views/tests/src/Functional/Handler/HandlerTest.php
@@ -32,6 +32,11 @@ class HandlerTest extends ViewTestBase {
    */
   public static $modules = ['views_ui', 'comment', 'node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp($import_test_views = TRUE) {
     parent::setUp($import_test_views);
     $this->drupalCreateContentType(['type' => 'page']);
diff --git a/core/modules/views/tests/src/Functional/Plugin/AccessTest.php b/core/modules/views/tests/src/Functional/Plugin/AccessTest.php
index 31a64cc1cf10..317d6da37456 100644
--- a/core/modules/views/tests/src/Functional/Plugin/AccessTest.php
+++ b/core/modules/views/tests/src/Functional/Plugin/AccessTest.php
@@ -29,6 +29,11 @@ class AccessTest extends ViewTestBase {
    */
   public static $modules = ['node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Web user for testing.
    *
diff --git a/core/modules/views/tests/src/Functional/Plugin/ArgumentDefaultTest.php b/core/modules/views/tests/src/Functional/Plugin/ArgumentDefaultTest.php
index a5eb2f02fe19..fe6ff11510f3 100644
--- a/core/modules/views/tests/src/Functional/Plugin/ArgumentDefaultTest.php
+++ b/core/modules/views/tests/src/Functional/Plugin/ArgumentDefaultTest.php
@@ -31,6 +31,11 @@ class ArgumentDefaultTest extends ViewTestBase {
     'test_argument_default_query_param',
     ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Modules to enable.
    *
diff --git a/core/modules/views/tests/src/Functional/Plugin/CacheTagTest.php b/core/modules/views/tests/src/Functional/Plugin/CacheTagTest.php
index 32081addb25e..1adba7d801bf 100644
--- a/core/modules/views/tests/src/Functional/Plugin/CacheTagTest.php
+++ b/core/modules/views/tests/src/Functional/Plugin/CacheTagTest.php
@@ -29,6 +29,11 @@ class CacheTagTest extends ViewTestBase {
    */
   public static $modules = ['node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The node storage.
    *
diff --git a/core/modules/views/tests/src/Functional/Plugin/CacheWebTest.php b/core/modules/views/tests/src/Functional/Plugin/CacheWebTest.php
index c919bcb8312f..016c0abd8c3c 100644
--- a/core/modules/views/tests/src/Functional/Plugin/CacheWebTest.php
+++ b/core/modules/views/tests/src/Functional/Plugin/CacheWebTest.php
@@ -31,6 +31,11 @@ class CacheWebTest extends ViewTestBase {
    */
   public static $modules = ['taxonomy'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/views/tests/src/Functional/Plugin/ContextualFiltersBlockContextTest.php b/core/modules/views/tests/src/Functional/Plugin/ContextualFiltersBlockContextTest.php
index 9db8d155f630..2dc22f75482e 100644
--- a/core/modules/views/tests/src/Functional/Plugin/ContextualFiltersBlockContextTest.php
+++ b/core/modules/views/tests/src/Functional/Plugin/ContextualFiltersBlockContextTest.php
@@ -23,6 +23,11 @@ class ContextualFiltersBlockContextTest extends ViewTestBase {
    */
   public static $modules = ['block', 'block_test_views', 'views_ui', 'node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/views/tests/src/Functional/Plugin/DisabledDisplayTest.php b/core/modules/views/tests/src/Functional/Plugin/DisabledDisplayTest.php
index a85612cca282..4fe00c745869 100644
--- a/core/modules/views/tests/src/Functional/Plugin/DisabledDisplayTest.php
+++ b/core/modules/views/tests/src/Functional/Plugin/DisabledDisplayTest.php
@@ -26,6 +26,11 @@ class DisabledDisplayTest extends ViewTestBase {
    */
   public static $modules = ['block', 'node', 'views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   protected function setUp($import_test_views = TRUE) {
     parent::setUp($import_test_views);
 
diff --git a/core/modules/views/tests/src/Functional/Plugin/DisplayAttachmentTest.php b/core/modules/views/tests/src/Functional/Plugin/DisplayAttachmentTest.php
index 44668447c783..a09faf12b9cc 100644
--- a/core/modules/views/tests/src/Functional/Plugin/DisplayAttachmentTest.php
+++ b/core/modules/views/tests/src/Functional/Plugin/DisplayAttachmentTest.php
@@ -27,6 +27,11 @@ class DisplayAttachmentTest extends ViewTestBase {
    */
   public static $modules = ['node', 'views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   protected function setUp($import_test_views = TRUE) {
     parent::setUp($import_test_views);
 
diff --git a/core/modules/views/tests/src/Functional/Plugin/DisplayEntityReferenceTest.php b/core/modules/views/tests/src/Functional/Plugin/DisplayEntityReferenceTest.php
index 817c51d7875a..8a9b32db121e 100644
--- a/core/modules/views/tests/src/Functional/Plugin/DisplayEntityReferenceTest.php
+++ b/core/modules/views/tests/src/Functional/Plugin/DisplayEntityReferenceTest.php
@@ -34,6 +34,11 @@ class DisplayEntityReferenceTest extends ViewTestBase {
    */
   public static $modules = ['entity_test', 'field', 'views_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The used field name in the test.
    *
diff --git a/core/modules/views/tests/src/Functional/Plugin/DisplayFeedTest.php b/core/modules/views/tests/src/Functional/Plugin/DisplayFeedTest.php
index b4afccd478ba..456450f80738 100644
--- a/core/modules/views/tests/src/Functional/Plugin/DisplayFeedTest.php
+++ b/core/modules/views/tests/src/Functional/Plugin/DisplayFeedTest.php
@@ -28,6 +28,11 @@ class DisplayFeedTest extends ViewTestBase {
    */
   public static $modules = ['block', 'node', 'views', 'views_test_rss'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   protected function setUp($import_test_views = TRUE) {
     parent::setUp($import_test_views);
 
diff --git a/core/modules/views/tests/src/Functional/Plugin/DisplayPageWebTest.php b/core/modules/views/tests/src/Functional/Plugin/DisplayPageWebTest.php
index 501d9226eeda..d361db0e4b12 100644
--- a/core/modules/views/tests/src/Functional/Plugin/DisplayPageWebTest.php
+++ b/core/modules/views/tests/src/Functional/Plugin/DisplayPageWebTest.php
@@ -29,6 +29,11 @@ class DisplayPageWebTest extends ViewTestBase {
    */
   public static $modules = ['menu_ui', 'block', 'views_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/views/tests/src/Functional/Plugin/DisplayTest.php b/core/modules/views/tests/src/Functional/Plugin/DisplayTest.php
index 44905a392653..1b2adc228cf7 100644
--- a/core/modules/views/tests/src/Functional/Plugin/DisplayTest.php
+++ b/core/modules/views/tests/src/Functional/Plugin/DisplayTest.php
@@ -28,6 +28,11 @@ class DisplayTest extends ViewTestBase {
    */
   public static $modules = ['views_ui', 'node', 'block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp($import_test_views = TRUE) {
     parent::setUp();
 
diff --git a/core/modules/views/tests/src/Functional/Plugin/ExposedFormCheckboxesTest.php b/core/modules/views/tests/src/Functional/Plugin/ExposedFormCheckboxesTest.php
index cecc8fabd2a8..f6bd8adae375 100644
--- a/core/modules/views/tests/src/Functional/Plugin/ExposedFormCheckboxesTest.php
+++ b/core/modules/views/tests/src/Functional/Plugin/ExposedFormCheckboxesTest.php
@@ -29,6 +29,11 @@ class ExposedFormCheckboxesTest extends ViewTestBase {
    */
   public static $modules = ['node', 'views_ui', 'taxonomy'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test terms.
    *
diff --git a/core/modules/views/tests/src/Functional/Plugin/ExposedFormTest.php b/core/modules/views/tests/src/Functional/Plugin/ExposedFormTest.php
index 53a0e4dda7e3..6240fb041212 100644
--- a/core/modules/views/tests/src/Functional/Plugin/ExposedFormTest.php
+++ b/core/modules/views/tests/src/Functional/Plugin/ExposedFormTest.php
@@ -33,6 +33,11 @@ class ExposedFormTest extends ViewTestBase {
    */
   public static $modules = ['node', 'views_ui', 'block', 'entity_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   protected function setUp($import_test_views = TRUE) {
     parent::setUp($import_test_views);
 
diff --git a/core/modules/views/tests/src/Functional/Plugin/FilterTest.php b/core/modules/views/tests/src/Functional/Plugin/FilterTest.php
index 90c00f786dd4..d968125deaef 100644
--- a/core/modules/views/tests/src/Functional/Plugin/FilterTest.php
+++ b/core/modules/views/tests/src/Functional/Plugin/FilterTest.php
@@ -29,6 +29,11 @@ class FilterTest extends ViewTestBase {
    */
   public static $modules = ['views_ui', 'node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp($import_test_views = TRUE) {
     parent::setUp($import_test_views);
 
diff --git a/core/modules/views/tests/src/Functional/Plugin/MenuLinkTest.php b/core/modules/views/tests/src/Functional/Plugin/MenuLinkTest.php
index 77591b44dde1..1bba00e1ba8a 100644
--- a/core/modules/views/tests/src/Functional/Plugin/MenuLinkTest.php
+++ b/core/modules/views/tests/src/Functional/Plugin/MenuLinkTest.php
@@ -26,6 +26,11 @@ class MenuLinkTest extends ViewTestBase {
    */
   public static $modules = ['views', 'views_ui', 'user', 'node', 'menu_ui', 'block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with permission to administer views, menus and view content.
    *
diff --git a/core/modules/views/tests/src/Functional/Plugin/MiniPagerTest.php b/core/modules/views/tests/src/Functional/Plugin/MiniPagerTest.php
index 492d22f98797..5ab9390f2e78 100644
--- a/core/modules/views/tests/src/Functional/Plugin/MiniPagerTest.php
+++ b/core/modules/views/tests/src/Functional/Plugin/MiniPagerTest.php
@@ -27,6 +27,11 @@ class MiniPagerTest extends ViewTestBase {
    */
   public static $modules = ['node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Nodes used by the test.
    *
diff --git a/core/modules/views/tests/src/Functional/Plugin/NumericFormatPluralTest.php b/core/modules/views/tests/src/Functional/Plugin/NumericFormatPluralTest.php
index c20fa6e5c6b9..57a2f8befe42 100644
--- a/core/modules/views/tests/src/Functional/Plugin/NumericFormatPluralTest.php
+++ b/core/modules/views/tests/src/Functional/Plugin/NumericFormatPluralTest.php
@@ -21,6 +21,11 @@ class NumericFormatPluralTest extends ViewTestBase {
    */
   public static $modules = ['views_ui', 'file', 'language', 'locale'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/views/tests/src/Functional/Plugin/PagerTest.php b/core/modules/views/tests/src/Functional/Plugin/PagerTest.php
index 56c37fb35768..c7c686740102 100644
--- a/core/modules/views/tests/src/Functional/Plugin/PagerTest.php
+++ b/core/modules/views/tests/src/Functional/Plugin/PagerTest.php
@@ -30,6 +30,11 @@ class PagerTest extends ViewTestBase {
    */
   public static $modules = ['node', 'views_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * String translation storage object.
    *
diff --git a/core/modules/views/tests/src/Functional/Plugin/StyleOpmlTest.php b/core/modules/views/tests/src/Functional/Plugin/StyleOpmlTest.php
index 90f027c7f50a..88fc6b59023b 100644
--- a/core/modules/views/tests/src/Functional/Plugin/StyleOpmlTest.php
+++ b/core/modules/views/tests/src/Functional/Plugin/StyleOpmlTest.php
@@ -26,6 +26,11 @@ class StyleOpmlTest extends ViewTestBase {
    */
   public static $modules = ['aggregator'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/views/tests/src/Functional/Plugin/StyleSummaryTest.php b/core/modules/views/tests/src/Functional/Plugin/StyleSummaryTest.php
index a2359b97344e..f39f6b43ac8c 100644
--- a/core/modules/views/tests/src/Functional/Plugin/StyleSummaryTest.php
+++ b/core/modules/views/tests/src/Functional/Plugin/StyleSummaryTest.php
@@ -17,6 +17,11 @@ class StyleSummaryTest extends ViewTestBase {
    */
   public static $modules = ['entity_test', 'views_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/views/tests/src/Functional/Plugin/StyleTableTest.php b/core/modules/views/tests/src/Functional/Plugin/StyleTableTest.php
index cbfd0288d4f5..3af722395d48 100644
--- a/core/modules/views/tests/src/Functional/Plugin/StyleTableTest.php
+++ b/core/modules/views/tests/src/Functional/Plugin/StyleTableTest.php
@@ -21,6 +21,11 @@ class StyleTableTest extends ViewTestBase {
    */
   public static $testViews = ['test_table'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/views/tests/src/Functional/Plugin/ViewsBulkTest.php b/core/modules/views/tests/src/Functional/Plugin/ViewsBulkTest.php
index e3faa88405fd..03a06428a0f2 100644
--- a/core/modules/views/tests/src/Functional/Plugin/ViewsBulkTest.php
+++ b/core/modules/views/tests/src/Functional/Plugin/ViewsBulkTest.php
@@ -25,6 +25,11 @@ class ViewsBulkTest extends ViewTestBase {
    */
   public static $modules = ['node', 'views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   public function setUp($import_test_views = TRUE) {
     parent::setUp($import_test_views);
 
diff --git a/core/modules/views/tests/src/Functional/Plugin/ViewsFormTest.php b/core/modules/views/tests/src/Functional/Plugin/ViewsFormTest.php
index 67c4cb035b78..d8556ca1bc9b 100644
--- a/core/modules/views/tests/src/Functional/Plugin/ViewsFormTest.php
+++ b/core/modules/views/tests/src/Functional/Plugin/ViewsFormTest.php
@@ -18,6 +18,11 @@ class ViewsFormTest extends ViewTestBase {
    */
   public static $modules = ['action_bulk_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the Views form wrapper.
    */
diff --git a/core/modules/views/tests/src/Functional/RenderCacheWebTest.php b/core/modules/views/tests/src/Functional/RenderCacheWebTest.php
index f8dfdd810da2..57e63999149f 100644
--- a/core/modules/views/tests/src/Functional/RenderCacheWebTest.php
+++ b/core/modules/views/tests/src/Functional/RenderCacheWebTest.php
@@ -16,6 +16,11 @@ class RenderCacheWebTest extends ViewTestBase {
    */
   public static $modules = ['node', 'block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/views/tests/src/Functional/Rest/ViewJsonAnonTest.php b/core/modules/views/tests/src/Functional/Rest/ViewJsonAnonTest.php
index 694aee165bc1..e7e7f76f6fdf 100644
--- a/core/modules/views/tests/src/Functional/Rest/ViewJsonAnonTest.php
+++ b/core/modules/views/tests/src/Functional/Rest/ViewJsonAnonTest.php
@@ -21,4 +21,9 @@ class ViewJsonAnonTest extends ViewResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/views/tests/src/Functional/Rest/ViewJsonBasicAuthTest.php b/core/modules/views/tests/src/Functional/Rest/ViewJsonBasicAuthTest.php
index 4ebe08c3367c..c6078203dad9 100644
--- a/core/modules/views/tests/src/Functional/Rest/ViewJsonBasicAuthTest.php
+++ b/core/modules/views/tests/src/Functional/Rest/ViewJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class ViewJsonBasicAuthTest extends ViewResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/views/tests/src/Functional/Rest/ViewJsonCookieTest.php b/core/modules/views/tests/src/Functional/Rest/ViewJsonCookieTest.php
index feeeab260277..e772c4bbcb50 100644
--- a/core/modules/views/tests/src/Functional/Rest/ViewJsonCookieTest.php
+++ b/core/modules/views/tests/src/Functional/Rest/ViewJsonCookieTest.php
@@ -26,4 +26,9 @@ class ViewJsonCookieTest extends ViewResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/views/tests/src/Functional/Rest/ViewXmlAnonTest.php b/core/modules/views/tests/src/Functional/Rest/ViewXmlAnonTest.php
index 7582a54f056f..ad94fec6d9ba 100644
--- a/core/modules/views/tests/src/Functional/Rest/ViewXmlAnonTest.php
+++ b/core/modules/views/tests/src/Functional/Rest/ViewXmlAnonTest.php
@@ -23,4 +23,9 @@ class ViewXmlAnonTest extends ViewResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/views/tests/src/Functional/Rest/ViewXmlBasicAuthTest.php b/core/modules/views/tests/src/Functional/Rest/ViewXmlBasicAuthTest.php
index ba9e58b3e6b1..52ab59f0b11e 100644
--- a/core/modules/views/tests/src/Functional/Rest/ViewXmlBasicAuthTest.php
+++ b/core/modules/views/tests/src/Functional/Rest/ViewXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class ViewXmlBasicAuthTest extends ViewResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/views/tests/src/Functional/Rest/ViewXmlCookieTest.php b/core/modules/views/tests/src/Functional/Rest/ViewXmlCookieTest.php
index 8f362a06c140..4f5e9169b31c 100644
--- a/core/modules/views/tests/src/Functional/Rest/ViewXmlCookieTest.php
+++ b/core/modules/views/tests/src/Functional/Rest/ViewXmlCookieTest.php
@@ -28,4 +28,9 @@ class ViewXmlCookieTest extends ViewResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/views/tests/src/Functional/SearchIntegrationTest.php b/core/modules/views/tests/src/Functional/SearchIntegrationTest.php
index fbbc96582b72..134417329d1b 100644
--- a/core/modules/views/tests/src/Functional/SearchIntegrationTest.php
+++ b/core/modules/views/tests/src/Functional/SearchIntegrationTest.php
@@ -21,6 +21,11 @@ class SearchIntegrationTest extends ViewTestBase {
    */
   public static $modules = ['node', 'search'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/views/tests/src/Functional/SearchMultilingualTest.php b/core/modules/views/tests/src/Functional/SearchMultilingualTest.php
index e7763e5362c5..78a6c3f2c617 100644
--- a/core/modules/views/tests/src/Functional/SearchMultilingualTest.php
+++ b/core/modules/views/tests/src/Functional/SearchMultilingualTest.php
@@ -22,6 +22,11 @@ class SearchMultilingualTest extends ViewTestBase {
    */
   public static $modules = ['node', 'search', 'language', 'content_translation'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/views/tests/src/Functional/TaxonomyGlossaryTest.php b/core/modules/views/tests/src/Functional/TaxonomyGlossaryTest.php
index 6e9d477677b0..65f8e0236692 100644
--- a/core/modules/views/tests/src/Functional/TaxonomyGlossaryTest.php
+++ b/core/modules/views/tests/src/Functional/TaxonomyGlossaryTest.php
@@ -20,6 +20,11 @@ class TaxonomyGlossaryTest extends ViewTestBase {
    */
   public static $modules = ['taxonomy'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/views/tests/src/Functional/UserBatchActionTest.php b/core/modules/views/tests/src/Functional/UserBatchActionTest.php
index 60c1d255876c..efb78079ae7e 100644
--- a/core/modules/views/tests/src/Functional/UserBatchActionTest.php
+++ b/core/modules/views/tests/src/Functional/UserBatchActionTest.php
@@ -19,6 +19,11 @@ class UserBatchActionTest extends BrowserTestBase {
    */
   public static $modules = ['user', 'user_batch_action_test', 'views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests user admin batch.
    */
diff --git a/core/modules/views/tests/src/Functional/UserPathTest.php b/core/modules/views/tests/src/Functional/UserPathTest.php
index 27a0f27a9bba..d31452bdae44 100644
--- a/core/modules/views/tests/src/Functional/UserPathTest.php
+++ b/core/modules/views/tests/src/Functional/UserPathTest.php
@@ -14,6 +14,11 @@ class UserPathTest extends ViewTestBase {
    */
   public static $modules = ['views', 'user'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The test views to use.
    *
diff --git a/core/modules/views/tests/src/Functional/ViewAjaxTest.php b/core/modules/views/tests/src/Functional/ViewAjaxTest.php
index 9f8c6022181c..32236d8f55c7 100644
--- a/core/modules/views/tests/src/Functional/ViewAjaxTest.php
+++ b/core/modules/views/tests/src/Functional/ViewAjaxTest.php
@@ -18,6 +18,11 @@ class ViewAjaxTest extends ViewTestBase {
    */
   public static $testViews = ['test_ajax_view', 'test_view'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp($import_test_views = TRUE) {
     parent::setUp($import_test_views);
 
diff --git a/core/modules/views/tests/src/Functional/ViewElementTest.php b/core/modules/views/tests/src/Functional/ViewElementTest.php
index 2dbc54f6b505..b682df7604bd 100644
--- a/core/modules/views/tests/src/Functional/ViewElementTest.php
+++ b/core/modules/views/tests/src/Functional/ViewElementTest.php
@@ -18,6 +18,11 @@ class ViewElementTest extends ViewTestBase {
    */
   public static $testViews = ['test_view_embed'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/views/tests/src/Functional/ViewsEscapingTest.php b/core/modules/views/tests/src/Functional/ViewsEscapingTest.php
index d66d90863c52..c10ff8144b18 100644
--- a/core/modules/views/tests/src/Functional/ViewsEscapingTest.php
+++ b/core/modules/views/tests/src/Functional/ViewsEscapingTest.php
@@ -16,6 +16,11 @@ class ViewsEscapingTest extends ViewTestBase {
    */
   public static $testViews = ['test_page_display', 'test_field_header'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Used by WebTestBase::setup()
    *
diff --git a/core/modules/views/tests/src/Functional/ViewsFormMultipleTest.php b/core/modules/views/tests/src/Functional/ViewsFormMultipleTest.php
index c4c709e3bfc6..5d420cf04de5 100644
--- a/core/modules/views/tests/src/Functional/ViewsFormMultipleTest.php
+++ b/core/modules/views/tests/src/Functional/ViewsFormMultipleTest.php
@@ -16,6 +16,11 @@ class ViewsFormMultipleTest extends ViewTestBase {
    */
   public static $testViews = ['test_form_multiple'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/views/tests/src/Functional/ViewsNoResultsBehaviorTest.php b/core/modules/views/tests/src/Functional/ViewsNoResultsBehaviorTest.php
index bb8a77eca29a..be15beb8ce8e 100644
--- a/core/modules/views/tests/src/Functional/ViewsNoResultsBehaviorTest.php
+++ b/core/modules/views/tests/src/Functional/ViewsNoResultsBehaviorTest.php
@@ -16,6 +16,11 @@ class ViewsNoResultsBehaviorTest extends ViewTestBase {
    */
   public static $modules = ['node', 'user'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/views/tests/src/Functional/ViewsThemeIntegrationTest.php b/core/modules/views/tests/src/Functional/ViewsThemeIntegrationTest.php
index 5807dad53518..3dcfa00b41fa 100644
--- a/core/modules/views/tests/src/Functional/ViewsThemeIntegrationTest.php
+++ b/core/modules/views/tests/src/Functional/ViewsThemeIntegrationTest.php
@@ -18,6 +18,11 @@ class ViewsThemeIntegrationTest extends ViewTestBase {
    */
   public static $testViews = ['test_page_display'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 
   /**
    * Used by WebTestBase::setup()
diff --git a/core/modules/views/tests/src/Functional/Wizard/BasicTest.php b/core/modules/views/tests/src/Functional/Wizard/BasicTest.php
index 8b92beba1a66..79cf695fedcd 100644
--- a/core/modules/views/tests/src/Functional/Wizard/BasicTest.php
+++ b/core/modules/views/tests/src/Functional/Wizard/BasicTest.php
@@ -14,6 +14,11 @@
  */
 class BasicTest extends WizardTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp($import_test_views = TRUE) {
     parent::setUp($import_test_views);
 
diff --git a/core/modules/views/tests/src/Functional/Wizard/EntityTestRevisionTest.php b/core/modules/views/tests/src/Functional/Wizard/EntityTestRevisionTest.php
index 2c5f52fcae31..2e59b61dbd27 100644
--- a/core/modules/views/tests/src/Functional/Wizard/EntityTestRevisionTest.php
+++ b/core/modules/views/tests/src/Functional/Wizard/EntityTestRevisionTest.php
@@ -14,6 +14,11 @@ class EntityTestRevisionTest extends WizardTestBase {
    */
   public static $modules = ['entity_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests creating a view of revisions where the type is not on the base table.
    */
diff --git a/core/modules/views/tests/src/Functional/Wizard/ItemsPerPageTest.php b/core/modules/views/tests/src/Functional/Wizard/ItemsPerPageTest.php
index b42baf5cd063..4ab72da1df27 100644
--- a/core/modules/views/tests/src/Functional/Wizard/ItemsPerPageTest.php
+++ b/core/modules/views/tests/src/Functional/Wizard/ItemsPerPageTest.php
@@ -10,6 +10,11 @@
  */
 class ItemsPerPageTest extends WizardTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp($import_test_views = TRUE) {
     parent::setUp($import_test_views);
 
diff --git a/core/modules/views/tests/src/Functional/Wizard/MenuTest.php b/core/modules/views/tests/src/Functional/Wizard/MenuTest.php
index eb106f60e1f4..98f7d619df4e 100644
--- a/core/modules/views/tests/src/Functional/Wizard/MenuTest.php
+++ b/core/modules/views/tests/src/Functional/Wizard/MenuTest.php
@@ -12,6 +12,11 @@
  */
 class MenuTest extends WizardTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the menu functionality.
    */
diff --git a/core/modules/views/tests/src/Functional/Wizard/NodeWizardTest.php b/core/modules/views/tests/src/Functional/Wizard/NodeWizardTest.php
index 21bdf1709da6..6f2454623133 100644
--- a/core/modules/views/tests/src/Functional/Wizard/NodeWizardTest.php
+++ b/core/modules/views/tests/src/Functional/Wizard/NodeWizardTest.php
@@ -10,6 +10,11 @@
  */
 class NodeWizardTest extends WizardTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests creating a view with node titles.
    */
diff --git a/core/modules/views/tests/src/Functional/Wizard/PagerTest.php b/core/modules/views/tests/src/Functional/Wizard/PagerTest.php
index c8c697c08145..92bc0035ed0e 100644
--- a/core/modules/views/tests/src/Functional/Wizard/PagerTest.php
+++ b/core/modules/views/tests/src/Functional/Wizard/PagerTest.php
@@ -9,6 +9,11 @@
  */
 class PagerTest extends WizardTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the pager option.
    */
diff --git a/core/modules/views/tests/src/Functional/Wizard/SortingTest.php b/core/modules/views/tests/src/Functional/Wizard/SortingTest.php
index ee36bf2f7ad7..af8b0a12c939 100644
--- a/core/modules/views/tests/src/Functional/Wizard/SortingTest.php
+++ b/core/modules/views/tests/src/Functional/Wizard/SortingTest.php
@@ -9,6 +9,11 @@
  */
 class SortingTest extends WizardTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp($import_test_views = TRUE) {
     parent::setUp($import_test_views);
 
diff --git a/core/modules/views/tests/src/Functional/Wizard/TaggedWithTest.php b/core/modules/views/tests/src/Functional/Wizard/TaggedWithTest.php
index 0a8d67424877..4eee68c7607a 100644
--- a/core/modules/views/tests/src/Functional/Wizard/TaggedWithTest.php
+++ b/core/modules/views/tests/src/Functional/Wizard/TaggedWithTest.php
@@ -23,6 +23,11 @@ class TaggedWithTest extends WizardTestBase {
    */
   public static $modules = ['taxonomy'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Node type with an autocomplete tagging field.
    *
diff --git a/core/modules/views/tests/src/FunctionalJavascript/BlockExposedFilterAJAXTest.php b/core/modules/views/tests/src/FunctionalJavascript/BlockExposedFilterAJAXTest.php
index c483ba0331a2..e2000b3f9733 100644
--- a/core/modules/views/tests/src/FunctionalJavascript/BlockExposedFilterAJAXTest.php
+++ b/core/modules/views/tests/src/FunctionalJavascript/BlockExposedFilterAJAXTest.php
@@ -24,6 +24,11 @@ class BlockExposedFilterAJAXTest extends WebDriverTestBase {
 
   public static $testViews = ['test_block_exposed_ajax', 'test_block_exposed_ajax_with_page'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/views/tests/src/FunctionalJavascript/ClickSortingAJAXTest.php b/core/modules/views/tests/src/FunctionalJavascript/ClickSortingAJAXTest.php
index c45255e543b6..19c48a7093c2 100644
--- a/core/modules/views/tests/src/FunctionalJavascript/ClickSortingAJAXTest.php
+++ b/core/modules/views/tests/src/FunctionalJavascript/ClickSortingAJAXTest.php
@@ -22,6 +22,11 @@ class ClickSortingAJAXTest extends WebDriverTestBase {
    */
   public static $modules = ['node', 'views', 'views_test_config'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   public static $testViews = ['test_content_ajax'];
 
   /**
diff --git a/core/modules/views/tests/src/FunctionalJavascript/ExposedFilterAJAXTest.php b/core/modules/views/tests/src/FunctionalJavascript/ExposedFilterAJAXTest.php
index 0ab4277c3140..0fa130156bb6 100644
--- a/core/modules/views/tests/src/FunctionalJavascript/ExposedFilterAJAXTest.php
+++ b/core/modules/views/tests/src/FunctionalJavascript/ExposedFilterAJAXTest.php
@@ -21,6 +21,11 @@ class ExposedFilterAJAXTest extends WebDriverTestBase {
    */
   public static $modules = ['node', 'views', 'views_test_modal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/views/tests/src/FunctionalJavascript/GlossaryViewTest.php b/core/modules/views/tests/src/FunctionalJavascript/GlossaryViewTest.php
index 8da67861ad6d..aff18ad34534 100644
--- a/core/modules/views/tests/src/FunctionalJavascript/GlossaryViewTest.php
+++ b/core/modules/views/tests/src/FunctionalJavascript/GlossaryViewTest.php
@@ -24,6 +24,11 @@ class GlossaryViewTest extends WebDriverTestBase {
    */
   public static $modules = ['language', 'node', 'views', 'views_test_config'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * @var array
    * The test Views to enable.
diff --git a/core/modules/views/tests/src/FunctionalJavascript/PaginationAJAXTest.php b/core/modules/views/tests/src/FunctionalJavascript/PaginationAJAXTest.php
index 8febc85c5f78..84f6936968e1 100644
--- a/core/modules/views/tests/src/FunctionalJavascript/PaginationAJAXTest.php
+++ b/core/modules/views/tests/src/FunctionalJavascript/PaginationAJAXTest.php
@@ -22,6 +22,11 @@ class PaginationAJAXTest extends WebDriverTestBase {
    */
   public static $modules = ['node', 'views', 'views_test_config'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * @var array
    * Test Views to enable.
diff --git a/core/modules/views/tests/src/FunctionalJavascript/Plugin/views/Handler/ContextualFilterTest.php b/core/modules/views/tests/src/FunctionalJavascript/Plugin/views/Handler/ContextualFilterTest.php
index f0ac6085487c..baf00034ed59 100644
--- a/core/modules/views/tests/src/FunctionalJavascript/Plugin/views/Handler/ContextualFilterTest.php
+++ b/core/modules/views/tests/src/FunctionalJavascript/Plugin/views/Handler/ContextualFilterTest.php
@@ -17,6 +17,11 @@ class ContextualFilterTest extends WebDriverTestBase {
    */
   public static $modules = ['node', 'views', 'views_ui', 'views_test_config'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/views/tests/src/FunctionalJavascript/Plugin/views/Handler/FieldTest.php b/core/modules/views/tests/src/FunctionalJavascript/Plugin/views/Handler/FieldTest.php
index 079fe99ee4af..b28ba577b6e0 100644
--- a/core/modules/views/tests/src/FunctionalJavascript/Plugin/views/Handler/FieldTest.php
+++ b/core/modules/views/tests/src/FunctionalJavascript/Plugin/views/Handler/FieldTest.php
@@ -21,6 +21,11 @@ class FieldTest extends WebDriverTestBase {
    */
   public static $modules = ['node', 'views', 'views_ui', 'views_test_config'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/views/tests/src/FunctionalJavascript/Plugin/views/Handler/GroupedExposedFilterTest.php b/core/modules/views/tests/src/FunctionalJavascript/Plugin/views/Handler/GroupedExposedFilterTest.php
index 1bc8a486d32e..e61e8eaff368 100644
--- a/core/modules/views/tests/src/FunctionalJavascript/Plugin/views/Handler/GroupedExposedFilterTest.php
+++ b/core/modules/views/tests/src/FunctionalJavascript/Plugin/views/Handler/GroupedExposedFilterTest.php
@@ -19,6 +19,11 @@ class GroupedExposedFilterTest extends WebDriverTestBase {
    */
   public static $modules = ['node', 'views', 'views_ui', 'user', 'views_test_config'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/views_ui/tests/src/Functional/AnalyzeTest.php b/core/modules/views_ui/tests/src/Functional/AnalyzeTest.php
index 2492944235cb..ac2a8b13f227 100644
--- a/core/modules/views_ui/tests/src/Functional/AnalyzeTest.php
+++ b/core/modules/views_ui/tests/src/Functional/AnalyzeTest.php
@@ -18,6 +18,11 @@ class AnalyzeTest extends UITestBase {
    */
   public static $modules = ['views_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/views_ui/tests/src/Functional/AreaEntityUITest.php b/core/modules/views_ui/tests/src/Functional/AreaEntityUITest.php
index 4e39164c308f..305315c8027e 100644
--- a/core/modules/views_ui/tests/src/Functional/AreaEntityUITest.php
+++ b/core/modules/views_ui/tests/src/Functional/AreaEntityUITest.php
@@ -19,6 +19,11 @@ class AreaEntityUITest extends UITestBase {
    */
   public static $modules = ['entity_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   public function testUI() {
     // Set up a block and a entity_test entity.
     $block = Block::create(['id' => 'test_id', 'plugin' => 'system_main_block']);
diff --git a/core/modules/views_ui/tests/src/Functional/ArgumentValidatorTest.php b/core/modules/views_ui/tests/src/Functional/ArgumentValidatorTest.php
index 5a33970f7b22..b5bfe30474a3 100644
--- a/core/modules/views_ui/tests/src/Functional/ArgumentValidatorTest.php
+++ b/core/modules/views_ui/tests/src/Functional/ArgumentValidatorTest.php
@@ -18,6 +18,11 @@ class ArgumentValidatorTest extends UITestBase {
    */
   public static $testViews = ['test_argument'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the 'Specify validation criteria' checkbox functionality.
    */
diff --git a/core/modules/views_ui/tests/src/Functional/CachedDataUITest.php b/core/modules/views_ui/tests/src/Functional/CachedDataUITest.php
index 1ef4ca2f95bc..e50005f49e5f 100644
--- a/core/modules/views_ui/tests/src/Functional/CachedDataUITest.php
+++ b/core/modules/views_ui/tests/src/Functional/CachedDataUITest.php
@@ -16,6 +16,11 @@ class CachedDataUITest extends UITestBase {
    */
   public static $testViews = ['test_view'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the shared tempstore views data in the UI.
    */
diff --git a/core/modules/views_ui/tests/src/Functional/CustomBooleanTest.php b/core/modules/views_ui/tests/src/Functional/CustomBooleanTest.php
index a8219a34b7a1..5d4dcdea2f63 100644
--- a/core/modules/views_ui/tests/src/Functional/CustomBooleanTest.php
+++ b/core/modules/views_ui/tests/src/Functional/CustomBooleanTest.php
@@ -20,6 +20,11 @@ class CustomBooleanTest extends UITestBase {
    */
   public static $testViews = ['test_view'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * \Drupal\views\Tests\ViewTestBase::viewsData().
    */
diff --git a/core/modules/views_ui/tests/src/Functional/DefaultViewsTest.php b/core/modules/views_ui/tests/src/Functional/DefaultViewsTest.php
index 6fe73093ca66..7a4ad1eaa4d5 100644
--- a/core/modules/views_ui/tests/src/Functional/DefaultViewsTest.php
+++ b/core/modules/views_ui/tests/src/Functional/DefaultViewsTest.php
@@ -21,6 +21,11 @@ class DefaultViewsTest extends UITestBase {
    */
   public static $testViews = ['test_view_status', 'test_page_display_menu', 'test_page_display_arguments'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp($import_test_views = TRUE) {
     parent::setUp($import_test_views);
 
diff --git a/core/modules/views_ui/tests/src/Functional/DisplayAttachmentTest.php b/core/modules/views_ui/tests/src/Functional/DisplayAttachmentTest.php
index 537cedf656eb..bcbf4b709bb3 100644
--- a/core/modules/views_ui/tests/src/Functional/DisplayAttachmentTest.php
+++ b/core/modules/views_ui/tests/src/Functional/DisplayAttachmentTest.php
@@ -21,6 +21,11 @@ class DisplayAttachmentTest extends UITestBase {
    */
   public static $testViews = ['test_attachment_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the attachment UI.
    */
diff --git a/core/modules/views_ui/tests/src/Functional/DisplayCRUDTest.php b/core/modules/views_ui/tests/src/Functional/DisplayCRUDTest.php
index c1c7cef441ca..23a355709a30 100644
--- a/core/modules/views_ui/tests/src/Functional/DisplayCRUDTest.php
+++ b/core/modules/views_ui/tests/src/Functional/DisplayCRUDTest.php
@@ -25,6 +25,11 @@ class DisplayCRUDTest extends UITestBase {
    */
   public static $modules = ['contextual'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests adding a display.
    */
diff --git a/core/modules/views_ui/tests/src/Functional/DisplayExtenderUITest.php b/core/modules/views_ui/tests/src/Functional/DisplayExtenderUITest.php
index b222f15d7a69..9a4edbc3b6b6 100644
--- a/core/modules/views_ui/tests/src/Functional/DisplayExtenderUITest.php
+++ b/core/modules/views_ui/tests/src/Functional/DisplayExtenderUITest.php
@@ -18,6 +18,11 @@ class DisplayExtenderUITest extends UITestBase {
    */
   public static $testViews = ['test_view'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the display extender UI.
    */
diff --git a/core/modules/views_ui/tests/src/Functional/DisplayFeedTest.php b/core/modules/views_ui/tests/src/Functional/DisplayFeedTest.php
index 9dba45010f09..8394193df06e 100644
--- a/core/modules/views_ui/tests/src/Functional/DisplayFeedTest.php
+++ b/core/modules/views_ui/tests/src/Functional/DisplayFeedTest.php
@@ -24,6 +24,11 @@ class DisplayFeedTest extends UITestBase {
    */
   public static $modules = ['views_ui', 'aggregator'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests feed display admin UI.
    */
diff --git a/core/modules/views_ui/tests/src/Functional/DisplayPathTest.php b/core/modules/views_ui/tests/src/Functional/DisplayPathTest.php
index 5973a5d59bfc..cdf36704cf35 100644
--- a/core/modules/views_ui/tests/src/Functional/DisplayPathTest.php
+++ b/core/modules/views_ui/tests/src/Functional/DisplayPathTest.php
@@ -27,6 +27,11 @@ protected function setUp($import_test_views = TRUE) {
    */
   public static $modules = ['menu_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/views_ui/tests/src/Functional/DisplayTest.php b/core/modules/views_ui/tests/src/Functional/DisplayTest.php
index 8fa5a80de387..44d74a218594 100644
--- a/core/modules/views_ui/tests/src/Functional/DisplayTest.php
+++ b/core/modules/views_ui/tests/src/Functional/DisplayTest.php
@@ -27,6 +27,11 @@ class DisplayTest extends UITestBase {
    */
   public static $modules = ['contextual'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests adding a display.
    */
diff --git a/core/modules/views_ui/tests/src/Functional/DuplicateTest.php b/core/modules/views_ui/tests/src/Functional/DuplicateTest.php
index 91d88fa60c54..cddd7d666765 100644
--- a/core/modules/views_ui/tests/src/Functional/DuplicateTest.php
+++ b/core/modules/views_ui/tests/src/Functional/DuplicateTest.php
@@ -9,6 +9,11 @@
  */
 class DuplicateTest extends UITestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp($import_test_views = TRUE) {
     parent::setUp($import_test_views);
 
diff --git a/core/modules/views_ui/tests/src/Functional/ExposedFormUITest.php b/core/modules/views_ui/tests/src/Functional/ExposedFormUITest.php
index 0822eb833c91..c863d9362c80 100644
--- a/core/modules/views_ui/tests/src/Functional/ExposedFormUITest.php
+++ b/core/modules/views_ui/tests/src/Functional/ExposedFormUITest.php
@@ -23,6 +23,11 @@ class ExposedFormUITest extends UITestBase {
    */
   public static $modules = ['node', 'views_ui', 'block', 'taxonomy', 'field_ui', 'datetime'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Array of error message strings raised by the grouped form.
    *
diff --git a/core/modules/views_ui/tests/src/Functional/FieldUITest.php b/core/modules/views_ui/tests/src/Functional/FieldUITest.php
index dc3081f6505f..4c52aea7cccc 100644
--- a/core/modules/views_ui/tests/src/Functional/FieldUITest.php
+++ b/core/modules/views_ui/tests/src/Functional/FieldUITest.php
@@ -13,6 +13,11 @@
  */
 class FieldUITest extends UITestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/views_ui/tests/src/Functional/FilterBooleanWebTest.php b/core/modules/views_ui/tests/src/Functional/FilterBooleanWebTest.php
index e6adfeea7132..f62c8c0ae886 100644
--- a/core/modules/views_ui/tests/src/Functional/FilterBooleanWebTest.php
+++ b/core/modules/views_ui/tests/src/Functional/FilterBooleanWebTest.php
@@ -17,6 +17,11 @@ class FilterBooleanWebTest extends UITestBase {
    */
   public static $testViews = ['test_view'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the filter boolean UI.
    */
diff --git a/core/modules/views_ui/tests/src/Functional/FilterNumericWebTest.php b/core/modules/views_ui/tests/src/Functional/FilterNumericWebTest.php
index 8dc568de9bdf..eac88e4dd22b 100644
--- a/core/modules/views_ui/tests/src/Functional/FilterNumericWebTest.php
+++ b/core/modules/views_ui/tests/src/Functional/FilterNumericWebTest.php
@@ -20,6 +20,11 @@ class FilterNumericWebTest extends UITestBase {
    */
   public static $testViews = ['test_view'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the filter numeric UI.
    */
diff --git a/core/modules/views_ui/tests/src/Functional/FilterUITest.php b/core/modules/views_ui/tests/src/Functional/FilterUITest.php
index 9b7bbcde1187..6422bb4863ea 100644
--- a/core/modules/views_ui/tests/src/Functional/FilterUITest.php
+++ b/core/modules/views_ui/tests/src/Functional/FilterUITest.php
@@ -24,6 +24,11 @@ class FilterUITest extends UITestBase {
    */
   public static $modules = ['views_ui', 'node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/views_ui/tests/src/Functional/GroupByTest.php b/core/modules/views_ui/tests/src/Functional/GroupByTest.php
index 6a348b70d4a1..e79ff9d20892 100644
--- a/core/modules/views_ui/tests/src/Functional/GroupByTest.php
+++ b/core/modules/views_ui/tests/src/Functional/GroupByTest.php
@@ -16,6 +16,11 @@ class GroupByTest extends UITestBase {
    */
   public static $testViews = ['test_views_groupby_save'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests whether basic saving works.
    *
diff --git a/core/modules/views_ui/tests/src/Functional/HandlerTest.php b/core/modules/views_ui/tests/src/Functional/HandlerTest.php
index e37c61f4665e..557a9920274a 100644
--- a/core/modules/views_ui/tests/src/Functional/HandlerTest.php
+++ b/core/modules/views_ui/tests/src/Functional/HandlerTest.php
@@ -21,6 +21,11 @@ class HandlerTest extends UITestBase {
    */
   public static $modules = ['node_test_views'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Views used by this test.
    *
diff --git a/core/modules/views_ui/tests/src/Functional/NewViewConfigSchemaTest.php b/core/modules/views_ui/tests/src/Functional/NewViewConfigSchemaTest.php
index ef493ff8c894..58b0bdfdd938 100644
--- a/core/modules/views_ui/tests/src/Functional/NewViewConfigSchemaTest.php
+++ b/core/modules/views_ui/tests/src/Functional/NewViewConfigSchemaTest.php
@@ -16,6 +16,11 @@ class NewViewConfigSchemaTest extends UITestBase {
    */
   public static $modules = ['views_ui', 'node', 'comment', 'file', 'taxonomy', 'dblog', 'aggregator'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests creating brand new views.
    */
diff --git a/core/modules/views_ui/tests/src/Functional/OverrideDisplaysTest.php b/core/modules/views_ui/tests/src/Functional/OverrideDisplaysTest.php
index 24116d97ae2a..1bc982a1c5fa 100644
--- a/core/modules/views_ui/tests/src/Functional/OverrideDisplaysTest.php
+++ b/core/modules/views_ui/tests/src/Functional/OverrideDisplaysTest.php
@@ -9,6 +9,11 @@
  */
 class OverrideDisplaysTest extends UITestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function setUp($import_test_views = TRUE) {
     parent::setUp($import_test_views);
 
diff --git a/core/modules/views_ui/tests/src/Functional/PreviewTest.php b/core/modules/views_ui/tests/src/Functional/PreviewTest.php
index b76e464c8c34..a082c89231c8 100644
--- a/core/modules/views_ui/tests/src/Functional/PreviewTest.php
+++ b/core/modules/views_ui/tests/src/Functional/PreviewTest.php
@@ -16,6 +16,11 @@ class PreviewTest extends UITestBase {
    */
   public static $testViews = ['test_preview', 'test_preview_error', 'test_pager_full', 'test_mini_pager', 'test_click_sort'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Tests contextual links in the preview form.
    */
diff --git a/core/modules/views_ui/tests/src/Functional/QueryTest.php b/core/modules/views_ui/tests/src/Functional/QueryTest.php
index 0eb58ce7102d..d806e82262fe 100644
--- a/core/modules/views_ui/tests/src/Functional/QueryTest.php
+++ b/core/modules/views_ui/tests/src/Functional/QueryTest.php
@@ -19,6 +19,11 @@ class QueryTest extends UITestBase {
    */
   public static $testViews = ['test_view'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/views_ui/tests/src/Functional/RearrangeFieldsTest.php b/core/modules/views_ui/tests/src/Functional/RearrangeFieldsTest.php
index 125a7e928b8e..0ca4b57d194f 100644
--- a/core/modules/views_ui/tests/src/Functional/RearrangeFieldsTest.php
+++ b/core/modules/views_ui/tests/src/Functional/RearrangeFieldsTest.php
@@ -19,6 +19,11 @@ class RearrangeFieldsTest extends UITestBase {
    */
   public static $testViews = ['test_view'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Gets the fields from the View.
    */
diff --git a/core/modules/views_ui/tests/src/Functional/RedirectTest.php b/core/modules/views_ui/tests/src/Functional/RedirectTest.php
index 4df38cee9e30..b332b6a673d9 100644
--- a/core/modules/views_ui/tests/src/Functional/RedirectTest.php
+++ b/core/modules/views_ui/tests/src/Functional/RedirectTest.php
@@ -16,6 +16,11 @@ class RedirectTest extends UITestBase {
    */
   public static $testViews = ['test_view', 'test_redirect_view'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the redirecting.
    */
diff --git a/core/modules/views_ui/tests/src/Functional/ReportFieldsTest.php b/core/modules/views_ui/tests/src/Functional/ReportFieldsTest.php
index d2527d0b9da4..840e91f62106 100644
--- a/core/modules/views_ui/tests/src/Functional/ReportFieldsTest.php
+++ b/core/modules/views_ui/tests/src/Functional/ReportFieldsTest.php
@@ -17,6 +17,11 @@ class ReportFieldsTest extends UITestBase {
    */
   public static $testViews = ['test_field_field_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/views_ui/tests/src/Functional/ReportTest.php b/core/modules/views_ui/tests/src/Functional/ReportTest.php
index e7979930c1f7..5322e0108473 100644
--- a/core/modules/views_ui/tests/src/Functional/ReportTest.php
+++ b/core/modules/views_ui/tests/src/Functional/ReportTest.php
@@ -16,6 +16,11 @@ class ReportTest extends UITestBase {
    */
   public static $modules = ['views', 'views_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Stores an admin user used by the different tests.
    *
diff --git a/core/modules/views_ui/tests/src/Functional/RowUITest.php b/core/modules/views_ui/tests/src/Functional/RowUITest.php
index 8b256f4373eb..637bbb576d57 100644
--- a/core/modules/views_ui/tests/src/Functional/RowUITest.php
+++ b/core/modules/views_ui/tests/src/Functional/RowUITest.php
@@ -20,6 +20,11 @@ class RowUITest extends UITestBase {
    */
   public static $testViews = ['test_view'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests changing the row plugin and changing some options of a row.
    */
diff --git a/core/modules/views_ui/tests/src/Functional/SettingsTest.php b/core/modules/views_ui/tests/src/Functional/SettingsTest.php
index 1ac98c6e634f..d5ce503523f1 100644
--- a/core/modules/views_ui/tests/src/Functional/SettingsTest.php
+++ b/core/modules/views_ui/tests/src/Functional/SettingsTest.php
@@ -16,6 +16,11 @@ class SettingsTest extends UITestBase {
    */
   protected $adminUser;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/views_ui/tests/src/Functional/StorageTest.php b/core/modules/views_ui/tests/src/Functional/StorageTest.php
index 02f4fc77df7c..86708a93028a 100644
--- a/core/modules/views_ui/tests/src/Functional/StorageTest.php
+++ b/core/modules/views_ui/tests/src/Functional/StorageTest.php
@@ -20,6 +20,11 @@ class StorageTest extends UITestBase {
    */
   public static $testViews = ['test_view'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Modules to enable.
    *
diff --git a/core/modules/views_ui/tests/src/Functional/StyleTableTest.php b/core/modules/views_ui/tests/src/Functional/StyleTableTest.php
index d00df3302274..3efbbb7355ea 100644
--- a/core/modules/views_ui/tests/src/Functional/StyleTableTest.php
+++ b/core/modules/views_ui/tests/src/Functional/StyleTableTest.php
@@ -12,6 +12,11 @@
  */
 class StyleTableTest extends UITestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests created a table style view.
    */
diff --git a/core/modules/views_ui/tests/src/Functional/StyleUITest.php b/core/modules/views_ui/tests/src/Functional/StyleUITest.php
index 62f682a5f925..0bd7e98639c2 100644
--- a/core/modules/views_ui/tests/src/Functional/StyleUITest.php
+++ b/core/modules/views_ui/tests/src/Functional/StyleUITest.php
@@ -19,6 +19,11 @@ class StyleUITest extends UITestBase {
    */
   public static $testViews = ['test_view'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests changing the style plugin and changing some options of a style.
    */
diff --git a/core/modules/views_ui/tests/src/Functional/TokenizeAreaUITest.php b/core/modules/views_ui/tests/src/Functional/TokenizeAreaUITest.php
index df42d8e11d33..3a8bea6fae07 100644
--- a/core/modules/views_ui/tests/src/Functional/TokenizeAreaUITest.php
+++ b/core/modules/views_ui/tests/src/Functional/TokenizeAreaUITest.php
@@ -18,6 +18,11 @@ class TokenizeAreaUITest extends UITestBase {
    */
   public static $modules = ['entity_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test that the right tokens are shown as available for replacement.
    */
diff --git a/core/modules/views_ui/tests/src/Functional/TranslatedViewTest.php b/core/modules/views_ui/tests/src/Functional/TranslatedViewTest.php
index a8d3c8b96f51..d3c521b5eae0 100644
--- a/core/modules/views_ui/tests/src/Functional/TranslatedViewTest.php
+++ b/core/modules/views_ui/tests/src/Functional/TranslatedViewTest.php
@@ -21,6 +21,11 @@ class TranslatedViewTest extends UITestBase {
     'views_ui',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Languages to enable.
    *
diff --git a/core/modules/views_ui/tests/src/Functional/UnsavedPreviewTest.php b/core/modules/views_ui/tests/src/Functional/UnsavedPreviewTest.php
index 3265e1a2f564..96c3778446a9 100644
--- a/core/modules/views_ui/tests/src/Functional/UnsavedPreviewTest.php
+++ b/core/modules/views_ui/tests/src/Functional/UnsavedPreviewTest.php
@@ -16,6 +16,11 @@ class UnsavedPreviewTest extends UITestBase {
     */
   public static $testViews = ['content'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * An admin user with the 'administer views' permission.
    *
diff --git a/core/modules/views_ui/tests/src/Functional/ViewEditTest.php b/core/modules/views_ui/tests/src/Functional/ViewEditTest.php
index 645bac54a817..82eec0b60d3c 100644
--- a/core/modules/views_ui/tests/src/Functional/ViewEditTest.php
+++ b/core/modules/views_ui/tests/src/Functional/ViewEditTest.php
@@ -19,6 +19,11 @@ class ViewEditTest extends UITestBase {
    */
   public static $testViews = ['test_view', 'test_display', 'test_groupwise_term_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the delete link on a views UI.
    */
diff --git a/core/modules/views_ui/tests/src/Functional/ViewsListTest.php b/core/modules/views_ui/tests/src/Functional/ViewsListTest.php
index 956ab9bc0cb9..80ac1b8d0039 100644
--- a/core/modules/views_ui/tests/src/Functional/ViewsListTest.php
+++ b/core/modules/views_ui/tests/src/Functional/ViewsListTest.php
@@ -19,6 +19,11 @@ class ViewsListTest extends UITestBase {
    */
   public static $modules = ['block', 'views_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A user with permission to administer views.
    *
diff --git a/core/modules/views_ui/tests/src/Functional/ViewsUITourTest.php b/core/modules/views_ui/tests/src/Functional/ViewsUITourTest.php
index 8a2dd2953f3b..2dd089da7b3c 100644
--- a/core/modules/views_ui/tests/src/Functional/ViewsUITourTest.php
+++ b/core/modules/views_ui/tests/src/Functional/ViewsUITourTest.php
@@ -19,6 +19,11 @@ class ViewsUITourTest extends TourTestBase {
    */
   protected $adminUser;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * String translation storage object.
    *
diff --git a/core/modules/views_ui/tests/src/Functional/WizardTest.php b/core/modules/views_ui/tests/src/Functional/WizardTest.php
index 81154817ef99..855efeddc1df 100644
--- a/core/modules/views_ui/tests/src/Functional/WizardTest.php
+++ b/core/modules/views_ui/tests/src/Functional/WizardTest.php
@@ -14,6 +14,11 @@
  */
 class WizardTest extends WizardTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests filling in the wizard with really long strings.
    */
diff --git a/core/modules/views_ui/tests/src/Functional/XssTest.php b/core/modules/views_ui/tests/src/Functional/XssTest.php
index cabb48ebcfe3..3e7fc34b14e1 100644
--- a/core/modules/views_ui/tests/src/Functional/XssTest.php
+++ b/core/modules/views_ui/tests/src/Functional/XssTest.php
@@ -16,6 +16,11 @@ class XssTest extends UITestBase {
    */
   public static $modules = ['node', 'user', 'views_ui', 'views_ui_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   public function testViewsUi() {
     $this->drupalGet('admin/structure/views/view/sa_contrib_2013_035');
     $this->assertEscaped('<marquee>test</marquee>', 'Field admin label is properly escaped.');
diff --git a/core/modules/views_ui/tests/src/FunctionalJavascript/DisplayTest.php b/core/modules/views_ui/tests/src/FunctionalJavascript/DisplayTest.php
index 6b7cd1226f88..799bb8762141 100644
--- a/core/modules/views_ui/tests/src/FunctionalJavascript/DisplayTest.php
+++ b/core/modules/views_ui/tests/src/FunctionalJavascript/DisplayTest.php
@@ -28,6 +28,11 @@ class DisplayTest extends WebDriverTestBase {
     'views_test_config',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   public static $testViews = ['test_content_ajax', 'test_display'];
 
   /**
diff --git a/core/modules/views_ui/tests/src/FunctionalJavascript/FilterCriteriaTest.php b/core/modules/views_ui/tests/src/FunctionalJavascript/FilterCriteriaTest.php
index f12c4784320d..1f28058fa99c 100644
--- a/core/modules/views_ui/tests/src/FunctionalJavascript/FilterCriteriaTest.php
+++ b/core/modules/views_ui/tests/src/FunctionalJavascript/FilterCriteriaTest.php
@@ -16,6 +16,11 @@ class FilterCriteriaTest extends WebDriverTestBase {
    */
   public static $modules = ['node', 'views', 'views_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/views_ui/tests/src/FunctionalJavascript/FilterOptionsTest.php b/core/modules/views_ui/tests/src/FunctionalJavascript/FilterOptionsTest.php
index 6f2f6259682d..69c9021e172a 100644
--- a/core/modules/views_ui/tests/src/FunctionalJavascript/FilterOptionsTest.php
+++ b/core/modules/views_ui/tests/src/FunctionalJavascript/FilterOptionsTest.php
@@ -16,6 +16,11 @@ class FilterOptionsTest extends WebDriverTestBase {
    */
   public static $modules = ['node', 'views', 'views_ui', 'views_ui_test_field'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/views_ui/tests/src/FunctionalJavascript/LibraryCachingTest.php b/core/modules/views_ui/tests/src/FunctionalJavascript/LibraryCachingTest.php
index b1b158ba6ce3..c4e14c63cf29 100644
--- a/core/modules/views_ui/tests/src/FunctionalJavascript/LibraryCachingTest.php
+++ b/core/modules/views_ui/tests/src/FunctionalJavascript/LibraryCachingTest.php
@@ -16,6 +16,11 @@ class LibraryCachingTest extends WebDriverTestBase {
    */
   public static $modules = ['node', 'views', 'views_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests if the Views UI dialogs open on consecutive requests.
    */
diff --git a/core/modules/views_ui/tests/src/FunctionalJavascript/PreviewTest.php b/core/modules/views_ui/tests/src/FunctionalJavascript/PreviewTest.php
index 489a3748df44..ae33591b102a 100644
--- a/core/modules/views_ui/tests/src/FunctionalJavascript/PreviewTest.php
+++ b/core/modules/views_ui/tests/src/FunctionalJavascript/PreviewTest.php
@@ -31,6 +31,11 @@ class PreviewTest extends WebDriverTestBase {
     'views_test_config',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/views_ui/tests/src/FunctionalJavascript/ViewsListingTest.php b/core/modules/views_ui/tests/src/FunctionalJavascript/ViewsListingTest.php
index fc696c03a866..f6a9976dcf9a 100644
--- a/core/modules/views_ui/tests/src/FunctionalJavascript/ViewsListingTest.php
+++ b/core/modules/views_ui/tests/src/FunctionalJavascript/ViewsListingTest.php
@@ -17,6 +17,11 @@ class ViewsListingTest extends WebDriverTestBase {
    */
   public static $modules = ['node', 'views', 'views_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/views_ui/tests/src/FunctionalJavascript/ViewsWizardTest.php b/core/modules/views_ui/tests/src/FunctionalJavascript/ViewsWizardTest.php
index 16369f12fea1..33611fbe1e5a 100644
--- a/core/modules/views_ui/tests/src/FunctionalJavascript/ViewsWizardTest.php
+++ b/core/modules/views_ui/tests/src/FunctionalJavascript/ViewsWizardTest.php
@@ -17,6 +17,11 @@ class ViewsWizardTest extends WebDriverTestBase {
    */
   public static $modules = ['node', 'views', 'views_ui', 'block', 'user'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/workflows/tests/src/Functional/Hal/WorkflowHalJsonAnonTest.php b/core/modules/workflows/tests/src/Functional/Hal/WorkflowHalJsonAnonTest.php
index 0c2fe0046325..741970775c11 100644
--- a/core/modules/workflows/tests/src/Functional/Hal/WorkflowHalJsonAnonTest.php
+++ b/core/modules/workflows/tests/src/Functional/Hal/WorkflowHalJsonAnonTest.php
@@ -17,6 +17,11 @@ class WorkflowHalJsonAnonTest extends WorkflowResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/workflows/tests/src/Functional/Hal/WorkflowHalJsonBasicAuthTest.php b/core/modules/workflows/tests/src/Functional/Hal/WorkflowHalJsonBasicAuthTest.php
index b2e9807333a7..2a9c18bf165e 100644
--- a/core/modules/workflows/tests/src/Functional/Hal/WorkflowHalJsonBasicAuthTest.php
+++ b/core/modules/workflows/tests/src/Functional/Hal/WorkflowHalJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class WorkflowHalJsonBasicAuthTest extends WorkflowHalJsonAnonTest {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/workflows/tests/src/Functional/Hal/WorkflowHalJsonCookieTest.php b/core/modules/workflows/tests/src/Functional/Hal/WorkflowHalJsonCookieTest.php
index 94199e5fa482..db1a75c1d120 100644
--- a/core/modules/workflows/tests/src/Functional/Hal/WorkflowHalJsonCookieTest.php
+++ b/core/modules/workflows/tests/src/Functional/Hal/WorkflowHalJsonCookieTest.php
@@ -16,4 +16,9 @@ class WorkflowHalJsonCookieTest extends WorkflowHalJsonAnonTest {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/workflows/tests/src/Functional/Rest/WorkflowJsonAnonTest.php b/core/modules/workflows/tests/src/Functional/Rest/WorkflowJsonAnonTest.php
index edb7d0b556e7..4865353f8f54 100644
--- a/core/modules/workflows/tests/src/Functional/Rest/WorkflowJsonAnonTest.php
+++ b/core/modules/workflows/tests/src/Functional/Rest/WorkflowJsonAnonTest.php
@@ -21,4 +21,9 @@ class WorkflowJsonAnonTest extends WorkflowResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/workflows/tests/src/Functional/Rest/WorkflowJsonBasicAuthTest.php b/core/modules/workflows/tests/src/Functional/Rest/WorkflowJsonBasicAuthTest.php
index db687cfbb48b..0c979d6d6e2f 100644
--- a/core/modules/workflows/tests/src/Functional/Rest/WorkflowJsonBasicAuthTest.php
+++ b/core/modules/workflows/tests/src/Functional/Rest/WorkflowJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class WorkflowJsonBasicAuthTest extends WorkflowResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/workflows/tests/src/Functional/Rest/WorkflowJsonCookieTest.php b/core/modules/workflows/tests/src/Functional/Rest/WorkflowJsonCookieTest.php
index 19bd342503fd..42165deb536b 100644
--- a/core/modules/workflows/tests/src/Functional/Rest/WorkflowJsonCookieTest.php
+++ b/core/modules/workflows/tests/src/Functional/Rest/WorkflowJsonCookieTest.php
@@ -26,4 +26,9 @@ class WorkflowJsonCookieTest extends WorkflowResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/workflows/tests/src/Functional/Rest/WorkflowXmlAnonTest.php b/core/modules/workflows/tests/src/Functional/Rest/WorkflowXmlAnonTest.php
index a66cc7763bf1..dbd938d23009 100644
--- a/core/modules/workflows/tests/src/Functional/Rest/WorkflowXmlAnonTest.php
+++ b/core/modules/workflows/tests/src/Functional/Rest/WorkflowXmlAnonTest.php
@@ -23,4 +23,9 @@ class WorkflowXmlAnonTest extends WorkflowResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/workflows/tests/src/Functional/Rest/WorkflowXmlBasicAuthTest.php b/core/modules/workflows/tests/src/Functional/Rest/WorkflowXmlBasicAuthTest.php
index db443e4763cd..0f1bbb721915 100644
--- a/core/modules/workflows/tests/src/Functional/Rest/WorkflowXmlBasicAuthTest.php
+++ b/core/modules/workflows/tests/src/Functional/Rest/WorkflowXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class WorkflowXmlBasicAuthTest extends WorkflowResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/workflows/tests/src/Functional/Rest/WorkflowXmlCookieTest.php b/core/modules/workflows/tests/src/Functional/Rest/WorkflowXmlCookieTest.php
index 50ea707ba8b4..e5ad8f6d790b 100644
--- a/core/modules/workflows/tests/src/Functional/Rest/WorkflowXmlCookieTest.php
+++ b/core/modules/workflows/tests/src/Functional/Rest/WorkflowXmlCookieTest.php
@@ -28,4 +28,9 @@ class WorkflowXmlCookieTest extends WorkflowResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/workflows/tests/src/Functional/WorkflowCustomStateTransitionAccessTest.php b/core/modules/workflows/tests/src/Functional/WorkflowCustomStateTransitionAccessTest.php
index 327b17255816..c0b044ed791f 100644
--- a/core/modules/workflows/tests/src/Functional/WorkflowCustomStateTransitionAccessTest.php
+++ b/core/modules/workflows/tests/src/Functional/WorkflowCustomStateTransitionAccessTest.php
@@ -20,6 +20,11 @@ class WorkflowCustomStateTransitionAccessTest extends BrowserTestBase {
     'workflow_type_test',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A test admin user.
    *
diff --git a/core/modules/workflows/tests/src/Functional/WorkflowUiNoTypeTest.php b/core/modules/workflows/tests/src/Functional/WorkflowUiNoTypeTest.php
index 01c61ac6b00d..94c862e6b4ef 100644
--- a/core/modules/workflows/tests/src/Functional/WorkflowUiNoTypeTest.php
+++ b/core/modules/workflows/tests/src/Functional/WorkflowUiNoTypeTest.php
@@ -18,6 +18,11 @@ class WorkflowUiNoTypeTest extends BrowserTestBase {
    */
   public static $modules = ['workflows', 'block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/workflows/tests/src/Functional/WorkflowUiTest.php b/core/modules/workflows/tests/src/Functional/WorkflowUiTest.php
index 227ddd769a0c..5a6fa195a9e4 100644
--- a/core/modules/workflows/tests/src/Functional/WorkflowUiTest.php
+++ b/core/modules/workflows/tests/src/Functional/WorkflowUiTest.php
@@ -20,6 +20,11 @@ class WorkflowUiTest extends BrowserTestBase {
    */
   public static $modules = ['workflows', 'workflow_type_test', 'block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/workspaces/tests/src/Functional/EntityResource/WorkspaceJsonAnonTest.php b/core/modules/workspaces/tests/src/Functional/EntityResource/WorkspaceJsonAnonTest.php
index f44286f1262a..17c0e7ea0800 100644
--- a/core/modules/workspaces/tests/src/Functional/EntityResource/WorkspaceJsonAnonTest.php
+++ b/core/modules/workspaces/tests/src/Functional/EntityResource/WorkspaceJsonAnonTest.php
@@ -23,4 +23,9 @@ class WorkspaceJsonAnonTest extends WorkspaceResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/workspaces/tests/src/Functional/EntityResource/WorkspaceJsonBasicAuthTest.php b/core/modules/workspaces/tests/src/Functional/EntityResource/WorkspaceJsonBasicAuthTest.php
index 8be512a7935d..c8721232eb92 100644
--- a/core/modules/workspaces/tests/src/Functional/EntityResource/WorkspaceJsonBasicAuthTest.php
+++ b/core/modules/workspaces/tests/src/Functional/EntityResource/WorkspaceJsonBasicAuthTest.php
@@ -18,6 +18,11 @@ class WorkspaceJsonBasicAuthTest extends WorkspaceResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/workspaces/tests/src/Functional/EntityResource/WorkspaceJsonCookieTest.php b/core/modules/workspaces/tests/src/Functional/EntityResource/WorkspaceJsonCookieTest.php
index dfba4aeeb596..f7c230df2ca9 100644
--- a/core/modules/workspaces/tests/src/Functional/EntityResource/WorkspaceJsonCookieTest.php
+++ b/core/modules/workspaces/tests/src/Functional/EntityResource/WorkspaceJsonCookieTest.php
@@ -28,4 +28,9 @@ class WorkspaceJsonCookieTest extends WorkspaceResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/modules/workspaces/tests/src/Functional/EntityResource/WorkspaceXmlAnonTest.php b/core/modules/workspaces/tests/src/Functional/EntityResource/WorkspaceXmlAnonTest.php
index c87b438a2321..c2c5f3c5d4e3 100644
--- a/core/modules/workspaces/tests/src/Functional/EntityResource/WorkspaceXmlAnonTest.php
+++ b/core/modules/workspaces/tests/src/Functional/EntityResource/WorkspaceXmlAnonTest.php
@@ -25,6 +25,11 @@ class WorkspaceXmlAnonTest extends WorkspaceResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/workspaces/tests/src/Functional/EntityResource/WorkspaceXmlBasicAuthTest.php b/core/modules/workspaces/tests/src/Functional/EntityResource/WorkspaceXmlBasicAuthTest.php
index 8769d9e8bac1..8ba105cb82fc 100644
--- a/core/modules/workspaces/tests/src/Functional/EntityResource/WorkspaceXmlBasicAuthTest.php
+++ b/core/modules/workspaces/tests/src/Functional/EntityResource/WorkspaceXmlBasicAuthTest.php
@@ -20,6 +20,11 @@ class WorkspaceXmlBasicAuthTest extends WorkspaceResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/workspaces/tests/src/Functional/EntityResource/WorkspaceXmlCookieTest.php b/core/modules/workspaces/tests/src/Functional/EntityResource/WorkspaceXmlCookieTest.php
index c37a28376d05..c7066a8dadaf 100644
--- a/core/modules/workspaces/tests/src/Functional/EntityResource/WorkspaceXmlCookieTest.php
+++ b/core/modules/workspaces/tests/src/Functional/EntityResource/WorkspaceXmlCookieTest.php
@@ -30,6 +30,11 @@ class WorkspaceXmlCookieTest extends WorkspaceResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/workspaces/tests/src/Functional/PathWorkspacesTest.php b/core/modules/workspaces/tests/src/Functional/PathWorkspacesTest.php
index 78ae786c5276..1787815b1f60 100644
--- a/core/modules/workspaces/tests/src/Functional/PathWorkspacesTest.php
+++ b/core/modules/workspaces/tests/src/Functional/PathWorkspacesTest.php
@@ -21,6 +21,11 @@ class PathWorkspacesTest extends BrowserTestBase {
    */
   protected static $modules = ['block', 'content_translation', 'node', 'path', 'workspaces'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/workspaces/tests/src/Functional/WorkspaceBypassTest.php b/core/modules/workspaces/tests/src/Functional/WorkspaceBypassTest.php
index cbed0a5f3288..ce5aeceeb00e 100644
--- a/core/modules/workspaces/tests/src/Functional/WorkspaceBypassTest.php
+++ b/core/modules/workspaces/tests/src/Functional/WorkspaceBypassTest.php
@@ -20,6 +20,11 @@ class WorkspaceBypassTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'user', 'block', 'workspaces'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Verifies that a user can edit anything in a workspace they own.
    */
diff --git a/core/modules/workspaces/tests/src/Functional/WorkspaceCacheContextTest.php b/core/modules/workspaces/tests/src/Functional/WorkspaceCacheContextTest.php
index 8945a69176cd..517e6b8d7104 100644
--- a/core/modules/workspaces/tests/src/Functional/WorkspaceCacheContextTest.php
+++ b/core/modules/workspaces/tests/src/Functional/WorkspaceCacheContextTest.php
@@ -22,6 +22,11 @@ class WorkspaceCacheContextTest extends BrowserTestBase {
    */
   public static $modules = ['block', 'node', 'workspaces'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the 'workspace' cache context.
    */
diff --git a/core/modules/workspaces/tests/src/Functional/WorkspaceConcurrentEditingTest.php b/core/modules/workspaces/tests/src/Functional/WorkspaceConcurrentEditingTest.php
index 43e04f0d5ac9..6b53ae4109b2 100644
--- a/core/modules/workspaces/tests/src/Functional/WorkspaceConcurrentEditingTest.php
+++ b/core/modules/workspaces/tests/src/Functional/WorkspaceConcurrentEditingTest.php
@@ -18,6 +18,11 @@ class WorkspaceConcurrentEditingTest extends BrowserTestBase {
    */
   public static $modules = ['block', 'node', 'workspaces'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test editing a node in multiple workspaces.
    */
diff --git a/core/modules/workspaces/tests/src/Functional/WorkspacePermissionsTest.php b/core/modules/workspaces/tests/src/Functional/WorkspacePermissionsTest.php
index c70ceeac6688..99d2b0aaf409 100644
--- a/core/modules/workspaces/tests/src/Functional/WorkspacePermissionsTest.php
+++ b/core/modules/workspaces/tests/src/Functional/WorkspacePermissionsTest.php
@@ -19,6 +19,11 @@ class WorkspacePermissionsTest extends BrowserTestBase {
    */
   public static $modules = ['workspaces'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Verifies that a user can create but not edit a workspace.
    */
diff --git a/core/modules/workspaces/tests/src/Functional/WorkspaceSwitcherTest.php b/core/modules/workspaces/tests/src/Functional/WorkspaceSwitcherTest.php
index 63d7d8609f24..7c8c8fa30f37 100644
--- a/core/modules/workspaces/tests/src/Functional/WorkspaceSwitcherTest.php
+++ b/core/modules/workspaces/tests/src/Functional/WorkspaceSwitcherTest.php
@@ -20,6 +20,11 @@ class WorkspaceSwitcherTest extends BrowserTestBase {
    */
   public static $modules = ['block', 'workspaces'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/workspaces/tests/src/Functional/WorkspaceTest.php b/core/modules/workspaces/tests/src/Functional/WorkspaceTest.php
index a0f887706172..5fb3b6792b64 100644
--- a/core/modules/workspaces/tests/src/Functional/WorkspaceTest.php
+++ b/core/modules/workspaces/tests/src/Functional/WorkspaceTest.php
@@ -18,6 +18,11 @@ class WorkspaceTest extends BrowserTestBase {
    */
   public static $modules = ['workspaces', 'toolbar', 'field_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A test user.
    *
diff --git a/core/modules/workspaces/tests/src/Functional/WorkspaceViewTest.php b/core/modules/workspaces/tests/src/Functional/WorkspaceViewTest.php
index df1b3c8c57f0..7468511990a2 100644
--- a/core/modules/workspaces/tests/src/Functional/WorkspaceViewTest.php
+++ b/core/modules/workspaces/tests/src/Functional/WorkspaceViewTest.php
@@ -19,6 +19,11 @@ class WorkspaceViewTest extends BrowserTestBase {
    */
   public static $modules = ['workspaces'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Verifies that a user can view their own workspace.
    */
diff --git a/core/modules/workspaces/tests/src/Functional/WorkspacesUninstallTest.php b/core/modules/workspaces/tests/src/Functional/WorkspacesUninstallTest.php
index 7e09248c0b5d..975bacabf97f 100644
--- a/core/modules/workspaces/tests/src/Functional/WorkspacesUninstallTest.php
+++ b/core/modules/workspaces/tests/src/Functional/WorkspacesUninstallTest.php
@@ -21,6 +21,11 @@ class WorkspacesUninstallTest extends BrowserTestBase {
    */
   public static $modules = ['workspaces'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests deleting workspace entities and uninstalling Workspaces module.
    */
diff --git a/core/modules/workspaces/tests/src/FunctionalJavascript/WorkspaceToolbarIntegrationTest.php b/core/modules/workspaces/tests/src/FunctionalJavascript/WorkspaceToolbarIntegrationTest.php
index c0eb05728092..889f50261ab0 100644
--- a/core/modules/workspaces/tests/src/FunctionalJavascript/WorkspaceToolbarIntegrationTest.php
+++ b/core/modules/workspaces/tests/src/FunctionalJavascript/WorkspaceToolbarIntegrationTest.php
@@ -16,6 +16,11 @@ class WorkspaceToolbarIntegrationTest extends OffCanvasTestBase {
    */
   public static $modules = ['toolbar', 'workspaces'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/profiles/demo_umami/modules/demo_umami_content/tests/src/Functional/DefaultContentFilesAccessTest.php b/core/profiles/demo_umami/modules/demo_umami_content/tests/src/Functional/DefaultContentFilesAccessTest.php
index cda82219f46c..4a176df14b51 100644
--- a/core/profiles/demo_umami/modules/demo_umami_content/tests/src/Functional/DefaultContentFilesAccessTest.php
+++ b/core/profiles/demo_umami/modules/demo_umami_content/tests/src/Functional/DefaultContentFilesAccessTest.php
@@ -11,6 +11,11 @@
  */
 class DefaultContentFilesAccessTest extends BrowserTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that sample images, recipes and articles are not accessible.
    */
diff --git a/core/profiles/minimal/tests/src/Functional/MinimalTest.php b/core/profiles/minimal/tests/src/Functional/MinimalTest.php
index d743fee5f434..b0c587e937a7 100644
--- a/core/profiles/minimal/tests/src/Functional/MinimalTest.php
+++ b/core/profiles/minimal/tests/src/Functional/MinimalTest.php
@@ -17,6 +17,11 @@ class MinimalTest extends BrowserTestBase {
 
   protected $profile = 'minimal';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests Minimal installation profile.
    */
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxCallbacksTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxCallbacksTest.php
index ffdbd98eb91d..26e2343601bd 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxCallbacksTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxCallbacksTest.php
@@ -16,6 +16,11 @@ class AjaxCallbacksTest extends WebDriverTestBase {
    */
   public static $modules = ['ajax_forms_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests if Ajax callback works on date element.
    */
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxFormCacheTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxFormCacheTest.php
index 52e095267e76..00f01d751450 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxFormCacheTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxFormCacheTest.php
@@ -19,6 +19,11 @@ class AjaxFormCacheTest extends WebDriverTestBase {
    */
   public static $modules = ['ajax_test', 'ajax_forms_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the usage of form cache for AJAX forms.
    */
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxFormImageButtonTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxFormImageButtonTest.php
index 0865b79766a0..64034733cea4 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxFormImageButtonTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxFormImageButtonTest.php
@@ -16,6 +16,11 @@ class AjaxFormImageButtonTest extends WebDriverTestBase {
    */
   public static $modules = ['ajax_forms_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests image buttons can be operated with the keyboard ENTER key.
    */
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxFormPageCacheTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxFormPageCacheTest.php
index 5a167f729cb9..1ac000ce74da 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxFormPageCacheTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxFormPageCacheTest.php
@@ -16,6 +16,11 @@ class AjaxFormPageCacheTest extends WebDriverTestBase {
    */
   public static $modules = ['ajax_test', 'ajax_forms_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxInGroupTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxInGroupTest.php
index d70b68d8e510..a6bf4f2f4457 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxInGroupTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxInGroupTest.php
@@ -16,6 +16,11 @@ class AjaxInGroupTest extends WebDriverTestBase {
    */
   protected static $modules = ['ajax_forms_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxTest.php
index 5d11ce49b4bc..87e2f88cd5b3 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxTest.php
@@ -16,6 +16,11 @@ class AjaxTest extends WebDriverTestBase {
    */
   public static $modules = ['ajax_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   public function testAjaxWithAdminRoute() {
     \Drupal::service('theme_installer')->install(['stable', 'seven']);
     $theme_config = \Drupal::configFactory()->getEditable('system.theme');
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/BackwardCompatibilityTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/BackwardCompatibilityTest.php
index 9a45583b7c2c..4c2b94d9ed6d 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/BackwardCompatibilityTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/BackwardCompatibilityTest.php
@@ -18,6 +18,11 @@ class BackwardCompatibilityTest extends WebDriverTestBase {
     'js_ajax_test',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Ensures Drupal.Ajax.element_settings BC layer.
    */
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/CommandsTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/CommandsTest.php
index eca511d82239..8dee3fed6963 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/CommandsTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/CommandsTest.php
@@ -16,6 +16,11 @@ class CommandsTest extends WebDriverTestBase {
    */
   public static $modules = ['node', 'ajax_test', 'ajax_forms_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests the various Ajax Commands.
    */
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/DialogTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/DialogTest.php
index b0c655190d88..e6f7c666e10b 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/DialogTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/DialogTest.php
@@ -18,6 +18,11 @@ class DialogTest extends WebDriverTestBase {
    */
   protected static $modules = ['ajax_test', 'ajax_forms_test', 'contact'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Test sending non-JS and AJAX requests to open and manipulate modals.
    */
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/ElementValidationTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/ElementValidationTest.php
index 48bda56cdf93..ad85e98b2a09 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/ElementValidationTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/ElementValidationTest.php
@@ -16,6 +16,11 @@ class ElementValidationTest extends WebDriverTestBase {
    */
   public static $modules = ['ajax_test', 'ajax_forms_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Tries to post an Ajax change to a form that has a validated element.
    *
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/FormValuesTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/FormValuesTest.php
index d1a3e5c2b92c..0911bbe1d7e2 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/FormValuesTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/FormValuesTest.php
@@ -16,6 +16,11 @@ class FormValuesTest extends WebDriverTestBase {
    */
   public static $modules = ['node', 'ajax_test', 'ajax_forms_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/MessageCommandTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/MessageCommandTest.php
index 22cbbab76efb..04b824c57483 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/MessageCommandTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/MessageCommandTest.php
@@ -16,6 +16,11 @@ class MessageCommandTest extends WebDriverTestBase {
    */
   protected static $modules = ['ajax_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test AJAX MessageCommand use in a form.
    */
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/MultiFormTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/MultiFormTest.php
index 283223537c1b..0a1547f8f531 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/MultiFormTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/MultiFormTest.php
@@ -21,6 +21,11 @@ class MultiFormTest extends WebDriverTestBase {
    */
   public static $modules = ['node', 'form_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/ThrobberTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/ThrobberTest.php
index 3ece94942b67..d64e4f1b766b 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/ThrobberTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/ThrobberTest.php
@@ -22,6 +22,11 @@ class ThrobberTest extends WebDriverTestBase {
     'hold_test',
   ];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/BrowserWithJavascriptTest.php b/core/tests/Drupal/FunctionalJavascriptTests/BrowserWithJavascriptTest.php
index 76454f741c76..672b0488ff42 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/BrowserWithJavascriptTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/BrowserWithJavascriptTest.php
@@ -19,6 +19,11 @@ class BrowserWithJavascriptTest extends WebDriverTestBase {
    */
   public static $modules = ['test_page_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   public function testJavascript() {
     $this->drupalGet('<front>');
     $session = $this->getSession();
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/Core/Form/FormGroupingElementsTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Core/Form/FormGroupingElementsTest.php
index 1c76c26ea350..20acd677de54 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/Core/Form/FormGroupingElementsTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Core/Form/FormGroupingElementsTest.php
@@ -18,6 +18,11 @@ class FormGroupingElementsTest extends WebDriverTestBase {
    */
   public static $modules = ['form_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/Core/JsMessageTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Core/JsMessageTest.php
index 89c0b1ec024e..b99f32da1408 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/Core/JsMessageTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Core/JsMessageTest.php
@@ -17,6 +17,11 @@ class JsMessageTest extends WebDriverTestBase {
    */
   public static $modules = ['js_message_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/Core/MachineNameTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Core/MachineNameTest.php
index 4396a8b6e34d..aaa9440e75b6 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/Core/MachineNameTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Core/MachineNameTest.php
@@ -21,6 +21,11 @@ class MachineNameTest extends WebDriverTestBase {
    */
   public static $modules = ['node', 'form_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/Core/Session/SessionTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Core/Session/SessionTest.php
index f4a180038242..1ba1132bcfcc 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/Core/Session/SessionTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Core/Session/SessionTest.php
@@ -17,6 +17,11 @@ class SessionTest extends WebDriverTestBase {
    */
   public static $modules = ['menu_link_content', 'block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/Dialog/DialogPositionTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Dialog/DialogPositionTest.php
index 4bfe3e0b3ae1..280682341a54 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/Dialog/DialogPositionTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Dialog/DialogPositionTest.php
@@ -16,6 +16,11 @@ class DialogPositionTest extends WebDriverTestBase {
    */
   public static $modules = ['block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests if the dialog UI works properly with block layout page.
    */
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/EntityReference/EntityReferenceAutocompleteWidgetTest.php b/core/tests/Drupal/FunctionalJavascriptTests/EntityReference/EntityReferenceAutocompleteWidgetTest.php
index fe4c9cf6c643..0b86802c98a3 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/EntityReference/EntityReferenceAutocompleteWidgetTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/EntityReference/EntityReferenceAutocompleteWidgetTest.php
@@ -23,6 +23,11 @@ class EntityReferenceAutocompleteWidgetTest extends WebDriverTestBase {
    */
   public static $modules = ['node', 'field_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/JavascriptGetDrupalSettingsTest.php b/core/tests/Drupal/FunctionalJavascriptTests/JavascriptGetDrupalSettingsTest.php
index 72ab2e24c4b7..3016dd146825 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/JavascriptGetDrupalSettingsTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/JavascriptGetDrupalSettingsTest.php
@@ -14,6 +14,11 @@ class JavascriptGetDrupalSettingsTest extends WebDriverTestBase {
    */
   protected static $modules = ['test_page_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests retrieval of Drupal settings.
    *
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/TableDrag/TableDragTest.php b/core/tests/Drupal/FunctionalJavascriptTests/TableDrag/TableDragTest.php
index ee7fe96c2ba3..d9fa93034289 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/TableDrag/TableDragTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/TableDrag/TableDragTest.php
@@ -22,6 +22,11 @@ class TableDragTest extends WebDriverTestBase {
    */
   protected static $modules = ['tabledrag_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The state service.
    *
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/Tests/DrupalSelenium2DriverTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Tests/DrupalSelenium2DriverTest.php
index 02fcc6ebaf6e..687cbca4cabe 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/Tests/DrupalSelenium2DriverTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Tests/DrupalSelenium2DriverTest.php
@@ -23,6 +23,11 @@ class DrupalSelenium2DriverTest extends WebDriverTestBase {
    */
   protected static $modules = ['file', 'field_ui', 'entity_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/Tests/JSWebAssertTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Tests/JSWebAssertTest.php
index fa3a3d1aac23..14deebe63b76 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/Tests/JSWebAssertTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Tests/JSWebAssertTest.php
@@ -20,6 +20,11 @@ class JSWebAssertTest extends WebDriverTestBase {
    */
   public static $modules = ['js_webassert_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that JSWebAssert assertions work correctly.
    */
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/Tests/JSWebWithWebDriverAssertTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Tests/JSWebWithWebDriverAssertTest.php
index d31a9a51c3fd..18840e2a893a 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/Tests/JSWebWithWebDriverAssertTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Tests/JSWebWithWebDriverAssertTest.php
@@ -16,4 +16,9 @@ class JSWebWithWebDriverAssertTest extends JSWebAssertTest {
    */
   protected $minkDefaultDriverClass = DrupalSelenium2Driver::class;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/tests/Drupal/FunctionalTests/Bootstrap/UncaughtExceptionTest.php b/core/tests/Drupal/FunctionalTests/Bootstrap/UncaughtExceptionTest.php
index 1a0f19e971d7..61a6f2db04d0 100644
--- a/core/tests/Drupal/FunctionalTests/Bootstrap/UncaughtExceptionTest.php
+++ b/core/tests/Drupal/FunctionalTests/Bootstrap/UncaughtExceptionTest.php
@@ -40,6 +40,11 @@ class UncaughtExceptionTest extends BrowserTestBase {
    */
   public static $modules = ['error_service_test', 'error_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Breadcrumb/Breadcrumb404Test.php b/core/tests/Drupal/FunctionalTests/Breadcrumb/Breadcrumb404Test.php
index b29f2630c6c9..ef06f3a3fc37 100644
--- a/core/tests/Drupal/FunctionalTests/Breadcrumb/Breadcrumb404Test.php
+++ b/core/tests/Drupal/FunctionalTests/Breadcrumb/Breadcrumb404Test.php
@@ -19,6 +19,11 @@ class Breadcrumb404Test extends BrowserTestBase {
    */
   public static $modules = ['system', 'block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that different 404s don't create unnecessary cache entries.
    */
diff --git a/core/tests/Drupal/FunctionalTests/BrowserTestBaseTest.php b/core/tests/Drupal/FunctionalTests/BrowserTestBaseTest.php
index 3a94bddd76e6..95a84babaf7f 100644
--- a/core/tests/Drupal/FunctionalTests/BrowserTestBaseTest.php
+++ b/core/tests/Drupal/FunctionalTests/BrowserTestBaseTest.php
@@ -26,6 +26,11 @@ class BrowserTestBaseTest extends BrowserTestBase {
    */
   public static $modules = ['test_page_test', 'form_test', 'system_test', 'node'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Tests basic page test.
    */
diff --git a/core/tests/Drupal/FunctionalTests/BrowserTestBaseUserAgentTest.php b/core/tests/Drupal/FunctionalTests/BrowserTestBaseUserAgentTest.php
index 8468fd5af831..ac6d76063525 100644
--- a/core/tests/Drupal/FunctionalTests/BrowserTestBaseUserAgentTest.php
+++ b/core/tests/Drupal/FunctionalTests/BrowserTestBaseUserAgentTest.php
@@ -11,6 +11,11 @@
  */
 class BrowserTestBaseUserAgentTest extends BrowserTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The user agent string to use.
    *
diff --git a/core/tests/Drupal/FunctionalTests/Core/Config/SchemaConfigListenerTest.php b/core/tests/Drupal/FunctionalTests/Core/Config/SchemaConfigListenerTest.php
index 698a7d1a0347..b0061f4f7bfb 100644
--- a/core/tests/Drupal/FunctionalTests/Core/Config/SchemaConfigListenerTest.php
+++ b/core/tests/Drupal/FunctionalTests/Core/Config/SchemaConfigListenerTest.php
@@ -19,4 +19,9 @@ class SchemaConfigListenerTest extends BrowserTestBase {
    */
   public static $modules = ['config_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/tests/Drupal/FunctionalTests/Core/Test/ModuleInstallBatchTest.php b/core/tests/Drupal/FunctionalTests/Core/Test/ModuleInstallBatchTest.php
index 60c4356c391d..dc02499d5138 100644
--- a/core/tests/Drupal/FunctionalTests/Core/Test/ModuleInstallBatchTest.php
+++ b/core/tests/Drupal/FunctionalTests/Core/Test/ModuleInstallBatchTest.php
@@ -25,6 +25,11 @@ class ModuleInstallBatchTest extends BrowserTestBase {
    */
   public static $modules = ['test_batch_test', 'entity_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests loading entities created in a batch in test_batch_test_install().
    */
diff --git a/core/tests/Drupal/FunctionalTests/Datetime/TimestampAgoFormatterTest.php b/core/tests/Drupal/FunctionalTests/Datetime/TimestampAgoFormatterTest.php
index 6b592346abce..9dd96c79401e 100644
--- a/core/tests/Drupal/FunctionalTests/Datetime/TimestampAgoFormatterTest.php
+++ b/core/tests/Drupal/FunctionalTests/Datetime/TimestampAgoFormatterTest.php
@@ -41,6 +41,11 @@ class TimestampAgoFormatterTest extends BrowserTestBase {
    */
   public static $modules = ['entity_test', 'field_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Datetime/TimestampTest.php b/core/tests/Drupal/FunctionalTests/Datetime/TimestampTest.php
index 064be558b0c6..bf1ca56d5d87 100644
--- a/core/tests/Drupal/FunctionalTests/Datetime/TimestampTest.php
+++ b/core/tests/Drupal/FunctionalTests/Datetime/TimestampTest.php
@@ -43,6 +43,11 @@ class TimestampTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'entity_test', 'field_ui'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Entity/ContentEntityFormCorrectUserInputMappingOnFieldDeltaElementsTest.php b/core/tests/Drupal/FunctionalTests/Entity/ContentEntityFormCorrectUserInputMappingOnFieldDeltaElementsTest.php
index 6c88599d8a75..3248aadaf9ab 100644
--- a/core/tests/Drupal/FunctionalTests/Entity/ContentEntityFormCorrectUserInputMappingOnFieldDeltaElementsTest.php
+++ b/core/tests/Drupal/FunctionalTests/Entity/ContentEntityFormCorrectUserInputMappingOnFieldDeltaElementsTest.php
@@ -33,6 +33,11 @@ class ContentEntityFormCorrectUserInputMappingOnFieldDeltaElementsTest extends B
    */
   public static $modules = ['entity_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Entity/ContentEntityFormFieldValidationFilteringTest.php b/core/tests/Drupal/FunctionalTests/Entity/ContentEntityFormFieldValidationFilteringTest.php
index 3daa841d7ce3..615175269eab 100644
--- a/core/tests/Drupal/FunctionalTests/Entity/ContentEntityFormFieldValidationFilteringTest.php
+++ b/core/tests/Drupal/FunctionalTests/Entity/ContentEntityFormFieldValidationFilteringTest.php
@@ -50,6 +50,11 @@ class ContentEntityFormFieldValidationFilteringTest extends BrowserTestBase {
    */
   public static $modules = ['entity_test', 'field_test', 'file', 'image'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Entity/DeleteMultipleFormTest.php b/core/tests/Drupal/FunctionalTests/Entity/DeleteMultipleFormTest.php
index 45f88d680e26..ef57bd72af35 100644
--- a/core/tests/Drupal/FunctionalTests/Entity/DeleteMultipleFormTest.php
+++ b/core/tests/Drupal/FunctionalTests/Entity/DeleteMultipleFormTest.php
@@ -31,6 +31,11 @@ class DeleteMultipleFormTest extends BrowserTestBase {
    */
   public static $modules = ['entity_test', 'user', 'language'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/FolderTest.php b/core/tests/Drupal/FunctionalTests/FolderTest.php
index 4a66be98b567..c977672d3bf6 100644
--- a/core/tests/Drupal/FunctionalTests/FolderTest.php
+++ b/core/tests/Drupal/FunctionalTests/FolderTest.php
@@ -20,6 +20,11 @@ class FolderTest extends BrowserTestBase {
    */
   public static $modules = ['image'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   public function testFolderSetup() {
     $directory = 'public://styles';
     $this->assertTrue(\Drupal::service('file_system')->prepareDirectory($directory, FALSE), 'Directory created.');
diff --git a/core/tests/Drupal/FunctionalTests/GetTestMethodCallerExtendsTest.php b/core/tests/Drupal/FunctionalTests/GetTestMethodCallerExtendsTest.php
index 81ebb813cd32..123c22b57380 100644
--- a/core/tests/Drupal/FunctionalTests/GetTestMethodCallerExtendsTest.php
+++ b/core/tests/Drupal/FunctionalTests/GetTestMethodCallerExtendsTest.php
@@ -11,6 +11,11 @@
  */
 class GetTestMethodCallerExtendsTest extends GetTestMethodCallerTest {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * A test method that is not present in the parent class.
    */
@@ -18,7 +23,7 @@ public function testGetTestMethodCallerChildClass() {
     $method_caller = $this->getTestMethodCaller();
     $expected = [
       'file' => __FILE__,
-      'line' => 18,
+      'line' => 23,
       'function' => __CLASS__ . '->' . __FUNCTION__ . '()',
       'class' => BrowserTestBase::class,
       'object' => $this,
diff --git a/core/tests/Drupal/FunctionalTests/GetTestMethodCallerTest.php b/core/tests/Drupal/FunctionalTests/GetTestMethodCallerTest.php
index f40ff20e921a..9baad8f27b3b 100644
--- a/core/tests/Drupal/FunctionalTests/GetTestMethodCallerTest.php
+++ b/core/tests/Drupal/FunctionalTests/GetTestMethodCallerTest.php
@@ -11,6 +11,11 @@
  */
 class GetTestMethodCallerTest extends BrowserTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests BrowserTestBase::getTestMethodCaller().
    */
@@ -18,7 +23,7 @@ public function testGetTestMethodCaller() {
     $method_caller = $this->getTestMethodCaller();
     $expected = [
       'file' => __FILE__,
-      'line' => 18,
+      'line' => 23,
       'function' => __CLASS__ . '->' . __FUNCTION__ . '()',
       'class' => BrowserTestBase::class,
       'object' => $this,
diff --git a/core/tests/Drupal/FunctionalTests/Hal/BaseFieldOverrideHalJsonAnonTest.php b/core/tests/Drupal/FunctionalTests/Hal/BaseFieldOverrideHalJsonAnonTest.php
index 688f26b5f43f..254103a087a1 100644
--- a/core/tests/Drupal/FunctionalTests/Hal/BaseFieldOverrideHalJsonAnonTest.php
+++ b/core/tests/Drupal/FunctionalTests/Hal/BaseFieldOverrideHalJsonAnonTest.php
@@ -17,6 +17,11 @@ class BaseFieldOverrideHalJsonAnonTest extends BaseFieldOverrideResourceTestBase
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Hal/BaseFieldOverrideHalJsonBasicAuthTest.php b/core/tests/Drupal/FunctionalTests/Hal/BaseFieldOverrideHalJsonBasicAuthTest.php
index 84907fcc5782..3ebdd19b4d3e 100644
--- a/core/tests/Drupal/FunctionalTests/Hal/BaseFieldOverrideHalJsonBasicAuthTest.php
+++ b/core/tests/Drupal/FunctionalTests/Hal/BaseFieldOverrideHalJsonBasicAuthTest.php
@@ -17,6 +17,11 @@ class BaseFieldOverrideHalJsonBasicAuthTest extends BaseFieldOverrideResourceTes
    */
   public static $modules = ['hal', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Hal/BaseFieldOverrideHalJsonCookieTest.php b/core/tests/Drupal/FunctionalTests/Hal/BaseFieldOverrideHalJsonCookieTest.php
index e373bd824ba0..c119372abe0c 100644
--- a/core/tests/Drupal/FunctionalTests/Hal/BaseFieldOverrideHalJsonCookieTest.php
+++ b/core/tests/Drupal/FunctionalTests/Hal/BaseFieldOverrideHalJsonCookieTest.php
@@ -17,6 +17,11 @@ class BaseFieldOverrideHalJsonCookieTest extends BaseFieldOverrideResourceTestBa
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Hal/DateFormatHalJsonAnonTest.php b/core/tests/Drupal/FunctionalTests/Hal/DateFormatHalJsonAnonTest.php
index 443b607afa5e..06bea1c955b1 100644
--- a/core/tests/Drupal/FunctionalTests/Hal/DateFormatHalJsonAnonTest.php
+++ b/core/tests/Drupal/FunctionalTests/Hal/DateFormatHalJsonAnonTest.php
@@ -17,6 +17,11 @@ class DateFormatHalJsonAnonTest extends DateFormatResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Hal/DateFormatHalJsonBasicAuthTest.php b/core/tests/Drupal/FunctionalTests/Hal/DateFormatHalJsonBasicAuthTest.php
index afab361f3c94..106cc6877398 100644
--- a/core/tests/Drupal/FunctionalTests/Hal/DateFormatHalJsonBasicAuthTest.php
+++ b/core/tests/Drupal/FunctionalTests/Hal/DateFormatHalJsonBasicAuthTest.php
@@ -17,6 +17,11 @@ class DateFormatHalJsonBasicAuthTest extends DateFormatResourceTestBase {
    */
   public static $modules = ['hal', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Hal/DateFormatHalJsonCookieTest.php b/core/tests/Drupal/FunctionalTests/Hal/DateFormatHalJsonCookieTest.php
index 2b0fbd6a2e3f..17e01a7f7537 100644
--- a/core/tests/Drupal/FunctionalTests/Hal/DateFormatHalJsonCookieTest.php
+++ b/core/tests/Drupal/FunctionalTests/Hal/DateFormatHalJsonCookieTest.php
@@ -17,6 +17,11 @@ class DateFormatHalJsonCookieTest extends DateFormatResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Hal/EntityFormDisplayHalJsonAnonTest.php b/core/tests/Drupal/FunctionalTests/Hal/EntityFormDisplayHalJsonAnonTest.php
index 1729c456bd32..726971df204c 100644
--- a/core/tests/Drupal/FunctionalTests/Hal/EntityFormDisplayHalJsonAnonTest.php
+++ b/core/tests/Drupal/FunctionalTests/Hal/EntityFormDisplayHalJsonAnonTest.php
@@ -17,6 +17,11 @@ class EntityFormDisplayHalJsonAnonTest extends EntityFormDisplayResourceTestBase
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Hal/EntityFormDisplayHalJsonBasicAuthTest.php b/core/tests/Drupal/FunctionalTests/Hal/EntityFormDisplayHalJsonBasicAuthTest.php
index c8adf75796ef..4a051751c921 100644
--- a/core/tests/Drupal/FunctionalTests/Hal/EntityFormDisplayHalJsonBasicAuthTest.php
+++ b/core/tests/Drupal/FunctionalTests/Hal/EntityFormDisplayHalJsonBasicAuthTest.php
@@ -17,6 +17,11 @@ class EntityFormDisplayHalJsonBasicAuthTest extends EntityFormDisplayResourceTes
    */
   public static $modules = ['hal', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Hal/EntityFormDisplayHalJsonCookieTest.php b/core/tests/Drupal/FunctionalTests/Hal/EntityFormDisplayHalJsonCookieTest.php
index d519e4a8df0b..1a7aa235fef5 100644
--- a/core/tests/Drupal/FunctionalTests/Hal/EntityFormDisplayHalJsonCookieTest.php
+++ b/core/tests/Drupal/FunctionalTests/Hal/EntityFormDisplayHalJsonCookieTest.php
@@ -17,6 +17,11 @@ class EntityFormDisplayHalJsonCookieTest extends EntityFormDisplayResourceTestBa
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Hal/EntityFormModeHalJsonAnonTest.php b/core/tests/Drupal/FunctionalTests/Hal/EntityFormModeHalJsonAnonTest.php
index 85d3b6f1167b..fb729e522304 100644
--- a/core/tests/Drupal/FunctionalTests/Hal/EntityFormModeHalJsonAnonTest.php
+++ b/core/tests/Drupal/FunctionalTests/Hal/EntityFormModeHalJsonAnonTest.php
@@ -17,6 +17,11 @@ class EntityFormModeHalJsonAnonTest extends EntityFormModeResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Hal/EntityFormModeHalJsonBasicAuthTest.php b/core/tests/Drupal/FunctionalTests/Hal/EntityFormModeHalJsonBasicAuthTest.php
index 373a13eb66f4..7cc7e85f91c7 100644
--- a/core/tests/Drupal/FunctionalTests/Hal/EntityFormModeHalJsonBasicAuthTest.php
+++ b/core/tests/Drupal/FunctionalTests/Hal/EntityFormModeHalJsonBasicAuthTest.php
@@ -17,6 +17,11 @@ class EntityFormModeHalJsonBasicAuthTest extends EntityFormModeResourceTestBase
    */
   public static $modules = ['hal', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Hal/EntityFormModeHalJsonCookieTest.php b/core/tests/Drupal/FunctionalTests/Hal/EntityFormModeHalJsonCookieTest.php
index 2df80e31c24a..4c471c829458 100644
--- a/core/tests/Drupal/FunctionalTests/Hal/EntityFormModeHalJsonCookieTest.php
+++ b/core/tests/Drupal/FunctionalTests/Hal/EntityFormModeHalJsonCookieTest.php
@@ -17,6 +17,11 @@ class EntityFormModeHalJsonCookieTest extends EntityFormModeResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Hal/EntityViewDisplayHalJsonAnonTest.php b/core/tests/Drupal/FunctionalTests/Hal/EntityViewDisplayHalJsonAnonTest.php
index ff5feaef5eb3..0edefde3636a 100644
--- a/core/tests/Drupal/FunctionalTests/Hal/EntityViewDisplayHalJsonAnonTest.php
+++ b/core/tests/Drupal/FunctionalTests/Hal/EntityViewDisplayHalJsonAnonTest.php
@@ -17,6 +17,11 @@ class EntityViewDisplayHalJsonAnonTest extends EntityViewDisplayResourceTestBase
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Hal/EntityViewDisplayHalJsonBasicAuthTest.php b/core/tests/Drupal/FunctionalTests/Hal/EntityViewDisplayHalJsonBasicAuthTest.php
index 4ba2f444658f..841ec8e3b9d7 100644
--- a/core/tests/Drupal/FunctionalTests/Hal/EntityViewDisplayHalJsonBasicAuthTest.php
+++ b/core/tests/Drupal/FunctionalTests/Hal/EntityViewDisplayHalJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class EntityViewDisplayHalJsonBasicAuthTest extends EntityViewDisplayHalJsonAnon
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Hal/EntityViewDisplayHalJsonCookieTest.php b/core/tests/Drupal/FunctionalTests/Hal/EntityViewDisplayHalJsonCookieTest.php
index 9f822bf636fc..a45e86265d06 100644
--- a/core/tests/Drupal/FunctionalTests/Hal/EntityViewDisplayHalJsonCookieTest.php
+++ b/core/tests/Drupal/FunctionalTests/Hal/EntityViewDisplayHalJsonCookieTest.php
@@ -16,4 +16,9 @@ class EntityViewDisplayHalJsonCookieTest extends EntityViewDisplayHalJsonAnonTes
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/tests/Drupal/FunctionalTests/Hal/EntityViewModeHalJsonAnonTest.php b/core/tests/Drupal/FunctionalTests/Hal/EntityViewModeHalJsonAnonTest.php
index fdd5d7c46c44..5ec8cddab685 100644
--- a/core/tests/Drupal/FunctionalTests/Hal/EntityViewModeHalJsonAnonTest.php
+++ b/core/tests/Drupal/FunctionalTests/Hal/EntityViewModeHalJsonAnonTest.php
@@ -17,6 +17,11 @@ class EntityViewModeHalJsonAnonTest extends EntityViewModeResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Hal/EntityViewModeHalJsonBasicAuthTest.php b/core/tests/Drupal/FunctionalTests/Hal/EntityViewModeHalJsonBasicAuthTest.php
index e13ea25b032b..5d7b1b90fdde 100644
--- a/core/tests/Drupal/FunctionalTests/Hal/EntityViewModeHalJsonBasicAuthTest.php
+++ b/core/tests/Drupal/FunctionalTests/Hal/EntityViewModeHalJsonBasicAuthTest.php
@@ -17,6 +17,11 @@ class EntityViewModeHalJsonBasicAuthTest extends EntityViewModeResourceTestBase
    */
   public static $modules = ['hal', 'basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Hal/EntityViewModeHalJsonCookieTest.php b/core/tests/Drupal/FunctionalTests/Hal/EntityViewModeHalJsonCookieTest.php
index b5f4ad470f77..2f883089ad45 100644
--- a/core/tests/Drupal/FunctionalTests/Hal/EntityViewModeHalJsonCookieTest.php
+++ b/core/tests/Drupal/FunctionalTests/Hal/EntityViewModeHalJsonCookieTest.php
@@ -17,6 +17,11 @@ class EntityViewModeHalJsonCookieTest extends EntityViewModeResourceTestBase {
    */
   public static $modules = ['hal'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/HttpKernel/CorsIntegrationTest.php b/core/tests/Drupal/FunctionalTests/HttpKernel/CorsIntegrationTest.php
index cc43936d6f16..75ba6fc2296b 100644
--- a/core/tests/Drupal/FunctionalTests/HttpKernel/CorsIntegrationTest.php
+++ b/core/tests/Drupal/FunctionalTests/HttpKernel/CorsIntegrationTest.php
@@ -21,6 +21,11 @@ class CorsIntegrationTest extends BrowserTestBase {
    */
   public static $modules = ['system', 'test_page_test', 'page_cache'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   public function testCrossSiteRequest() {
     // Test default parameters.
     $cors_config = $this->container->getParameter('cors.config');
diff --git a/core/tests/Drupal/FunctionalTests/Image/ToolkitSetupFormTest.php b/core/tests/Drupal/FunctionalTests/Image/ToolkitSetupFormTest.php
index d501f1d98c2c..9c9720e177bb 100644
--- a/core/tests/Drupal/FunctionalTests/Image/ToolkitSetupFormTest.php
+++ b/core/tests/Drupal/FunctionalTests/Image/ToolkitSetupFormTest.php
@@ -25,6 +25,11 @@ class ToolkitSetupFormTest extends BrowserTestBase {
    */
   public static $modules = ['system', 'image_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Image/ToolkitTest.php b/core/tests/Drupal/FunctionalTests/Image/ToolkitTest.php
index 17c91158c265..e91dab4b2979 100644
--- a/core/tests/Drupal/FunctionalTests/Image/ToolkitTest.php
+++ b/core/tests/Drupal/FunctionalTests/Image/ToolkitTest.php
@@ -9,6 +9,11 @@
  */
 class ToolkitTest extends ToolkitTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Check that ImageToolkitManager::getAvailableToolkits() only returns
    * available toolkits.
diff --git a/core/tests/Drupal/FunctionalTests/Installer/DistributionProfileExistingSettingsTest.php b/core/tests/Drupal/FunctionalTests/Installer/DistributionProfileExistingSettingsTest.php
index ee97a023f401..d5194bdec11e 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/DistributionProfileExistingSettingsTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/DistributionProfileExistingSettingsTest.php
@@ -22,6 +22,11 @@ class DistributionProfileExistingSettingsTest extends InstallerTestBase {
    */
   protected $info;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Installer/DistributionProfileTest.php b/core/tests/Drupal/FunctionalTests/Installer/DistributionProfileTest.php
index dce7ef51178b..bb7801e7d9ea 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/DistributionProfileTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/DistributionProfileTest.php
@@ -18,6 +18,11 @@ class DistributionProfileTest extends InstallerTestBase {
    */
   protected $info;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected function prepareEnvironment() {
     parent::prepareEnvironment();
     $this->info = [
diff --git a/core/tests/Drupal/FunctionalTests/Installer/DistributionProfileTranslationQueryTest.php b/core/tests/Drupal/FunctionalTests/Installer/DistributionProfileTranslationQueryTest.php
index e4a447f5e6cf..0fc21f42b9ac 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/DistributionProfileTranslationQueryTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/DistributionProfileTranslationQueryTest.php
@@ -13,6 +13,11 @@
  */
 class DistributionProfileTranslationQueryTest extends InstallerTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Installer/DistributionProfileTranslationTest.php b/core/tests/Drupal/FunctionalTests/Installer/DistributionProfileTranslationTest.php
index ac6697a0276a..ec6d81146367 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/DistributionProfileTranslationTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/DistributionProfileTranslationTest.php
@@ -13,6 +13,11 @@
  */
 class DistributionProfileTranslationTest extends InstallerTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallProfileDependenciesBcTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallProfileDependenciesBcTest.php
index 41526333446f..2f3890efc014 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallProfileDependenciesBcTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallProfileDependenciesBcTest.php
@@ -12,6 +12,11 @@
  */
 class InstallProfileDependenciesBcTest extends BrowserTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallProfileDependenciesTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallProfileDependenciesTest.php
index 4ceb7f8af90e..1e397e069ec8 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallProfileDependenciesTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallProfileDependenciesTest.php
@@ -12,6 +12,11 @@
  */
 class InstallProfileDependenciesTest extends BrowserTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerConfigDirectorySetNoDirectoryErrorTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerConfigDirectorySetNoDirectoryErrorTest.php
index 0d955b6957c5..38a08bf3b876 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerConfigDirectorySetNoDirectoryErrorTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerConfigDirectorySetNoDirectoryErrorTest.php
@@ -11,6 +11,11 @@
  */
 class InstallerConfigDirectorySetNoDirectoryErrorTest extends InstallerTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The directory where the sync directory should be created during install.
    *
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerConfigDirectorySetNoDirectoryTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerConfigDirectorySetNoDirectoryTest.php
index dcb47b5ee340..5863d931f465 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerConfigDirectorySetNoDirectoryTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerConfigDirectorySetNoDirectoryTest.php
@@ -11,6 +11,11 @@
  */
 class InstallerConfigDirectorySetNoDirectoryTest extends InstallerTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The sync directory created during the install.
    *
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerCustomConfigDirectoryCreateTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerCustomConfigDirectoryCreateTest.php
index 9e7ab31578a2..ee8b68e18d48 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerCustomConfigDirectoryCreateTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerCustomConfigDirectoryCreateTest.php
@@ -12,6 +12,11 @@
  */
 class InstallerCustomConfigDirectoryCreateTest extends InstallerTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerDatabaseErrorMessagesTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerDatabaseErrorMessagesTest.php
index 69c209070389..021fbc9a221c 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerDatabaseErrorMessagesTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerDatabaseErrorMessagesTest.php
@@ -11,6 +11,11 @@
  */
 class InstallerDatabaseErrorMessagesTest extends InstallerTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerEmptySettingsTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerEmptySettingsTest.php
index 839009ecfbe4..2f3e5acc660e 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerEmptySettingsTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerEmptySettingsTest.php
@@ -9,6 +9,11 @@
  */
 class InstallerEmptySettingsTest extends InstallerTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigDirectoryTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigDirectoryTest.php
index ec6b72b48fc3..eae925a62af2 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigDirectoryTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigDirectoryTest.php
@@ -9,6 +9,11 @@
  */
 class InstallerExistingConfigDirectoryTest extends InstallerTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The expected file perms of the folder.
    *
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigMultilingualTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigMultilingualTest.php
index db05d32031e6..2feb840693d7 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigMultilingualTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigMultilingualTest.php
@@ -9,6 +9,11 @@
  */
 class InstallerExistingConfigMultilingualTest extends InstallerExistingConfigTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigNoConfigTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigNoConfigTest.php
index 01ddefa9048a..b19ee442677f 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigNoConfigTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigNoConfigTest.php
@@ -9,6 +9,11 @@
  */
 class InstallerExistingConfigNoConfigTest extends InstallerExistingConfigTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected $profile = 'no_config_profile';
 
   /**
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigNoSystemSiteTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigNoSystemSiteTest.php
index 4ac68d4e8637..42d1c11f6cb0 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigNoSystemSiteTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigNoSystemSiteTest.php
@@ -9,6 +9,11 @@
  */
 class InstallerExistingConfigNoSystemSiteTest extends InstallerExistingConfigTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigProfileHookInstall.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigProfileHookInstall.php
index 2d9d6cdfc121..09f377415353 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigProfileHookInstall.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigProfileHookInstall.php
@@ -11,6 +11,11 @@ class InstallerExistingConfigProfileHookInstall extends InstallerExistingConfigT
 
   protected $profile = 'config_profile_with_hook_install';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigSyncDirectoryMultilingualTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigSyncDirectoryMultilingualTest.php
index e223998ed7cf..42bf5b5fbb70 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigSyncDirectoryMultilingualTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigSyncDirectoryMultilingualTest.php
@@ -9,6 +9,11 @@
  */
 class InstallerExistingConfigSyncDirectoryMultilingualTest extends InstallerExistingConfigTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigSyncDirectoryProfileHookInstall.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigSyncDirectoryProfileHookInstall.php
index 63aea303de3b..38a06971fa21 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigSyncDirectoryProfileHookInstall.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigSyncDirectoryProfileHookInstall.php
@@ -9,6 +9,11 @@
  */
 class InstallerExistingConfigSyncDirectoryProfileHookInstall extends InstallerExistingConfigTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigSyncDriectoryProfileMismatchTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigSyncDriectoryProfileMismatchTest.php
index 54b25ee8de67..80b392a72a70 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigSyncDriectoryProfileMismatchTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigSyncDriectoryProfileMismatchTest.php
@@ -9,6 +9,11 @@
  */
 class InstallerExistingConfigSyncDriectoryProfileMismatchTest extends InstallerExistingConfigTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigTest.php
index c1e75a87aeb4..01e71cf85614 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingConfigTest.php
@@ -9,6 +9,11 @@
  */
 class InstallerExistingConfigTest extends InstallerExistingConfigTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingDatabaseSettingsTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingDatabaseSettingsTest.php
index caf8b48097ce..021abd42f745 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingDatabaseSettingsTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingDatabaseSettingsTest.php
@@ -12,6 +12,11 @@
  */
 class InstallerExistingDatabaseSettingsTest extends InstallerTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingInstallationTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingInstallationTest.php
index 7b29d4acc834..1c8bfb9e5cec 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingInstallationTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingInstallationTest.php
@@ -9,6 +9,11 @@
  */
 class InstallerExistingInstallationTest extends InstallerTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Verifies that Drupal can't be reinstalled while an existing installation is
    * available.
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingSettingsMismatchProfileTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingSettingsMismatchProfileTest.php
index 596f522fb842..acbd93047e4c 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingSettingsMismatchProfileTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingSettingsMismatchProfileTest.php
@@ -15,6 +15,11 @@
  */
 class InstallerExistingSettingsMismatchProfileTest extends InstallerTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    *
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingSettingsNoProfileTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingSettingsNoProfileTest.php
index 791135e7a0b1..42f354221205 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingSettingsNoProfileTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingSettingsNoProfileTest.php
@@ -13,6 +13,11 @@
  */
 class InstallerExistingSettingsNoProfileTest extends InstallerTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    *
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingSettingsReadOnlyMismatchProfileTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingSettingsReadOnlyMismatchProfileTest.php
index 46d6f8b94714..86ac0a5956f8 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingSettingsReadOnlyMismatchProfileTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingSettingsReadOnlyMismatchProfileTest.php
@@ -15,6 +15,11 @@
  */
 class InstallerExistingSettingsReadOnlyMismatchProfileTest extends InstallerTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    *
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingSettingsTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingSettingsTest.php
index 5af025e5ee4c..f5fb5dc225e4 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingSettingsTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerExistingSettingsTest.php
@@ -13,6 +13,11 @@
  */
 class InstallerExistingSettingsTest extends InstallerTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    *
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerLanguageDirectionTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerLanguageDirectionTest.php
index ac2c46297f04..48d50af4d1e8 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerLanguageDirectionTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerLanguageDirectionTest.php
@@ -9,6 +9,11 @@
  */
 class InstallerLanguageDirectionTest extends InstallerTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Overrides the language code the installer should use.
    *
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerLanguagePageTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerLanguagePageTest.php
index 5ea9692f341b..692dd314b1cb 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerLanguagePageTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerLanguagePageTest.php
@@ -11,6 +11,11 @@
  */
 class InstallerLanguagePageTest extends InstallerTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Installer step: Select language.
    */
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerNonEnglishProfileWithoutLocaleModuleTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerNonEnglishProfileWithoutLocaleModuleTest.php
index 1ae12c7115a8..ecfe255b9404 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerNonEnglishProfileWithoutLocaleModuleTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerNonEnglishProfileWithoutLocaleModuleTest.php
@@ -11,6 +11,11 @@
  */
 class InstallerNonEnglishProfileWithoutLocaleModuleTest extends InstallerTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The testing profile name.
    *
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerProfileRequirementsTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerProfileRequirementsTest.php
index 56e7e245370b..1dd1649e3ec7 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerProfileRequirementsTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerProfileRequirementsTest.php
@@ -9,6 +9,11 @@
  */
 class InstallerProfileRequirementsTest extends InstallerTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerSiteConfigProfileTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerSiteConfigProfileTest.php
index 791befd0468b..a0483aba0190 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerSiteConfigProfileTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerSiteConfigProfileTest.php
@@ -10,6 +10,11 @@
  */
 class InstallerSiteConfigProfileTest extends InstallerTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerSkipPermissionHardeningTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerSkipPermissionHardeningTest.php
index 5a09571b3993..f282de86785a 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerSkipPermissionHardeningTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerSkipPermissionHardeningTest.php
@@ -9,6 +9,11 @@
  */
 class InstallerSkipPermissionHardeningTest extends InstallerTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerTest.php
index 97d59d055376..1fd544948253 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerTest.php
@@ -9,6 +9,11 @@
  */
 class InstallerTest extends InstallerTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Ensures that the user page is available after installation.
    */
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerTranslationMultipleLanguageForeignTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerTranslationMultipleLanguageForeignTest.php
index 58100cdbf3d7..846aa212ffaa 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerTranslationMultipleLanguageForeignTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerTranslationMultipleLanguageForeignTest.php
@@ -9,6 +9,11 @@
  */
 class InstallerTranslationMultipleLanguageForeignTest extends InstallerTranslationMultipleLanguageTest {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Overrides the language code in which to install Drupal.
    *
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerTranslationMultipleLanguageKeepEnglishTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerTranslationMultipleLanguageKeepEnglishTest.php
index 3c103103a31e..5ff0f7521d73 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerTranslationMultipleLanguageKeepEnglishTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerTranslationMultipleLanguageKeepEnglishTest.php
@@ -9,6 +9,11 @@
  */
 class InstallerTranslationMultipleLanguageKeepEnglishTest extends InstallerTranslationMultipleLanguageForeignTest {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Switch to the multilingual testing profile with English kept.
    *
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerTranslationMultipleLanguageTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerTranslationMultipleLanguageTest.php
index dcd112ae19bc..0f06d17a5cf3 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerTranslationMultipleLanguageTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerTranslationMultipleLanguageTest.php
@@ -9,6 +9,11 @@
  */
 class InstallerTranslationMultipleLanguageTest extends InstallerTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Switch to the multilingual testing profile.
    *
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerTranslationQueryTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerTranslationQueryTest.php
index 152713b27325..5c1c14a98961 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerTranslationQueryTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerTranslationQueryTest.php
@@ -11,6 +11,11 @@
  */
 class InstallerTranslationQueryTest extends InstallerTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Overrides the language code in which to install Drupal.
    *
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerTranslationTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerTranslationTest.php
index 55ce6b534c7c..c38d4719fc89 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerTranslationTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerTranslationTest.php
@@ -12,6 +12,11 @@
  */
 class InstallerTranslationTest extends InstallerTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'classy';
+
   /**
    * Overrides the language code in which to install Drupal.
    *
diff --git a/core/tests/Drupal/FunctionalTests/Installer/MinimalInstallerTest.php b/core/tests/Drupal/FunctionalTests/Installer/MinimalInstallerTest.php
index baefe0fe1c6f..4ff32ec9d07f 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/MinimalInstallerTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/MinimalInstallerTest.php
@@ -18,6 +18,11 @@ class MinimalInstallerTest extends ConfigAfterInstallerTestBase {
    */
   protected $profile = 'minimal';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Ensures that the exported minimal configuration is up to date.
    */
diff --git a/core/tests/Drupal/FunctionalTests/Installer/MultipleDistributionsProfileTest.php b/core/tests/Drupal/FunctionalTests/Installer/MultipleDistributionsProfileTest.php
index 4ced7a704e51..a0f2069cba56 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/MultipleDistributionsProfileTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/MultipleDistributionsProfileTest.php
@@ -18,6 +18,11 @@ class MultipleDistributionsProfileTest extends InstallerTestBase {
    */
   protected $info;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Installer/SingleVisibleProfileTest.php b/core/tests/Drupal/FunctionalTests/Installer/SingleVisibleProfileTest.php
index a6366ee76079..02e60a817e7a 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/SingleVisibleProfileTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/SingleVisibleProfileTest.php
@@ -20,6 +20,11 @@ class SingleVisibleProfileTest extends InstallerTestBase {
    */
   protected $profile = NULL;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Installer/SiteNameTest.php b/core/tests/Drupal/FunctionalTests/Installer/SiteNameTest.php
index b77fe35a725a..44087f2004e8 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/SiteNameTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/SiteNameTest.php
@@ -18,6 +18,11 @@ class SiteNameTest extends BrowserTestBase {
    */
   protected $siteName;
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Installer/TestingProfileInstallTest.php b/core/tests/Drupal/FunctionalTests/Installer/TestingProfileInstallTest.php
index d18de97d5667..b358787ba98d 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/TestingProfileInstallTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/TestingProfileInstallTest.php
@@ -16,6 +16,11 @@ class TestingProfileInstallTest extends BrowserTestBase {
    */
   protected $profile = 'testing';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Ensure the Update module and its dependencies are installed.
    */
diff --git a/core/tests/Drupal/FunctionalTests/MailCaptureTest.php b/core/tests/Drupal/FunctionalTests/MailCaptureTest.php
index 0f48d79e0e04..74e2f07ef8c1 100644
--- a/core/tests/Drupal/FunctionalTests/MailCaptureTest.php
+++ b/core/tests/Drupal/FunctionalTests/MailCaptureTest.php
@@ -17,6 +17,11 @@ class MailCaptureTest extends BrowserTestBase {
     getMails as drupalGetMails;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Test to see if the wrapper function is executed correctly.
    */
diff --git a/core/tests/Drupal/FunctionalTests/Rest/BaseFieldOverrideJsonAnonTest.php b/core/tests/Drupal/FunctionalTests/Rest/BaseFieldOverrideJsonAnonTest.php
index d5a416ad85e6..6e75e823763a 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/BaseFieldOverrideJsonAnonTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/BaseFieldOverrideJsonAnonTest.php
@@ -21,4 +21,9 @@ class BaseFieldOverrideJsonAnonTest extends BaseFieldOverrideResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/tests/Drupal/FunctionalTests/Rest/BaseFieldOverrideJsonBasicAuthTest.php b/core/tests/Drupal/FunctionalTests/Rest/BaseFieldOverrideJsonBasicAuthTest.php
index c40de5517b3c..c922c8d6d1a6 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/BaseFieldOverrideJsonBasicAuthTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/BaseFieldOverrideJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class BaseFieldOverrideJsonBasicAuthTest extends BaseFieldOverrideResourceTestBa
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Rest/BaseFieldOverrideJsonCookieTest.php b/core/tests/Drupal/FunctionalTests/Rest/BaseFieldOverrideJsonCookieTest.php
index a60fdf493682..142cc6cb095c 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/BaseFieldOverrideJsonCookieTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/BaseFieldOverrideJsonCookieTest.php
@@ -26,4 +26,9 @@ class BaseFieldOverrideJsonCookieTest extends BaseFieldOverrideResourceTestBase
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/tests/Drupal/FunctionalTests/Rest/BaseFieldOverrideXmlAnonTest.php b/core/tests/Drupal/FunctionalTests/Rest/BaseFieldOverrideXmlAnonTest.php
index 7b995b425045..887c53fd42f6 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/BaseFieldOverrideXmlAnonTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/BaseFieldOverrideXmlAnonTest.php
@@ -23,4 +23,9 @@ class BaseFieldOverrideXmlAnonTest extends BaseFieldOverrideResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/tests/Drupal/FunctionalTests/Rest/BaseFieldOverrideXmlBasicAuthTest.php b/core/tests/Drupal/FunctionalTests/Rest/BaseFieldOverrideXmlBasicAuthTest.php
index 1e3f83356741..3a3f08bf5719 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/BaseFieldOverrideXmlBasicAuthTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/BaseFieldOverrideXmlBasicAuthTest.php
@@ -28,6 +28,11 @@ class BaseFieldOverrideXmlBasicAuthTest extends BaseFieldOverrideResourceTestBas
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Rest/BaseFieldOverrideXmlCookieTest.php b/core/tests/Drupal/FunctionalTests/Rest/BaseFieldOverrideXmlCookieTest.php
index ba1d166c826c..0aed06ffcb7f 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/BaseFieldOverrideXmlCookieTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/BaseFieldOverrideXmlCookieTest.php
@@ -28,4 +28,9 @@ class BaseFieldOverrideXmlCookieTest extends BaseFieldOverrideResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/tests/Drupal/FunctionalTests/Rest/DateFormatJsonAnonTest.php b/core/tests/Drupal/FunctionalTests/Rest/DateFormatJsonAnonTest.php
index ad53e9da2f2f..a114aa609a93 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/DateFormatJsonAnonTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/DateFormatJsonAnonTest.php
@@ -21,4 +21,9 @@ class DateFormatJsonAnonTest extends DateFormatResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/tests/Drupal/FunctionalTests/Rest/DateFormatJsonBasicAuthTest.php b/core/tests/Drupal/FunctionalTests/Rest/DateFormatJsonBasicAuthTest.php
index 453f8a192035..0ae83504a45f 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/DateFormatJsonBasicAuthTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/DateFormatJsonBasicAuthTest.php
@@ -26,6 +26,11 @@ class DateFormatJsonBasicAuthTest extends DateFormatResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Rest/DateFormatJsonCookieTest.php b/core/tests/Drupal/FunctionalTests/Rest/DateFormatJsonCookieTest.php
index 2c1548f32dbf..61e1ccaee5fe 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/DateFormatJsonCookieTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/DateFormatJsonCookieTest.php
@@ -26,4 +26,9 @@ class DateFormatJsonCookieTest extends DateFormatResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/tests/Drupal/FunctionalTests/Rest/DateFormatXmlAnonTest.php b/core/tests/Drupal/FunctionalTests/Rest/DateFormatXmlAnonTest.php
index 8eec7d4e8c00..47ea72b28f00 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/DateFormatXmlAnonTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/DateFormatXmlAnonTest.php
@@ -23,4 +23,9 @@ class DateFormatXmlAnonTest extends DateFormatResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/tests/Drupal/FunctionalTests/Rest/DateFormatXmlBasicAuthTest.php b/core/tests/Drupal/FunctionalTests/Rest/DateFormatXmlBasicAuthTest.php
index eb787a99b83c..8a09a33a8422 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/DateFormatXmlBasicAuthTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/DateFormatXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class DateFormatXmlBasicAuthTest extends DateFormatResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Rest/DateFormatXmlCookieTest.php b/core/tests/Drupal/FunctionalTests/Rest/DateFormatXmlCookieTest.php
index 124614d27d25..7fd076fda7c9 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/DateFormatXmlCookieTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/DateFormatXmlCookieTest.php
@@ -28,4 +28,9 @@ class DateFormatXmlCookieTest extends DateFormatResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/tests/Drupal/FunctionalTests/Rest/EntityFormDisplayJsonAnonTest.php b/core/tests/Drupal/FunctionalTests/Rest/EntityFormDisplayJsonAnonTest.php
index 9ae38d80d17d..b39205e65c5d 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/EntityFormDisplayJsonAnonTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/EntityFormDisplayJsonAnonTest.php
@@ -21,4 +21,9 @@ class EntityFormDisplayJsonAnonTest extends EntityFormDisplayResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/tests/Drupal/FunctionalTests/Rest/EntityFormDisplayJsonBasicAuthTest.php b/core/tests/Drupal/FunctionalTests/Rest/EntityFormDisplayJsonBasicAuthTest.php
index 36ca913eddae..a3871c845599 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/EntityFormDisplayJsonBasicAuthTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/EntityFormDisplayJsonBasicAuthTest.php
@@ -26,6 +26,11 @@ class EntityFormDisplayJsonBasicAuthTest extends EntityFormDisplayResourceTestBa
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Rest/EntityFormDisplayJsonCookieTest.php b/core/tests/Drupal/FunctionalTests/Rest/EntityFormDisplayJsonCookieTest.php
index 5154ababbaed..1fdebc9f81f2 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/EntityFormDisplayJsonCookieTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/EntityFormDisplayJsonCookieTest.php
@@ -26,4 +26,9 @@ class EntityFormDisplayJsonCookieTest extends EntityFormDisplayResourceTestBase
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/tests/Drupal/FunctionalTests/Rest/EntityFormDisplayXmlAnonTest.php b/core/tests/Drupal/FunctionalTests/Rest/EntityFormDisplayXmlAnonTest.php
index da1437ed123c..56375974cc33 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/EntityFormDisplayXmlAnonTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/EntityFormDisplayXmlAnonTest.php
@@ -23,4 +23,9 @@ class EntityFormDisplayXmlAnonTest extends EntityFormDisplayResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/tests/Drupal/FunctionalTests/Rest/EntityFormDisplayXmlBasicAuthTest.php b/core/tests/Drupal/FunctionalTests/Rest/EntityFormDisplayXmlBasicAuthTest.php
index 2edf2460a9a5..ba89d79e1f45 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/EntityFormDisplayXmlBasicAuthTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/EntityFormDisplayXmlBasicAuthTest.php
@@ -28,6 +28,11 @@ class EntityFormDisplayXmlBasicAuthTest extends EntityFormDisplayResourceTestBas
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Rest/EntityFormDisplayXmlCookieTest.php b/core/tests/Drupal/FunctionalTests/Rest/EntityFormDisplayXmlCookieTest.php
index e9e93b0d475e..391370ec8405 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/EntityFormDisplayXmlCookieTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/EntityFormDisplayXmlCookieTest.php
@@ -28,4 +28,9 @@ class EntityFormDisplayXmlCookieTest extends EntityFormDisplayResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/tests/Drupal/FunctionalTests/Rest/EntityFormModeJsonAnonTest.php b/core/tests/Drupal/FunctionalTests/Rest/EntityFormModeJsonAnonTest.php
index a1cea00f1f13..816e1e9af9ed 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/EntityFormModeJsonAnonTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/EntityFormModeJsonAnonTest.php
@@ -21,4 +21,9 @@ class EntityFormModeJsonAnonTest extends EntityFormModeResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/tests/Drupal/FunctionalTests/Rest/EntityFormModeJsonBasicAuthTest.php b/core/tests/Drupal/FunctionalTests/Rest/EntityFormModeJsonBasicAuthTest.php
index bbfb6fbc98ef..a813e1a2de36 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/EntityFormModeJsonBasicAuthTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/EntityFormModeJsonBasicAuthTest.php
@@ -26,6 +26,11 @@ class EntityFormModeJsonBasicAuthTest extends EntityFormModeResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Rest/EntityFormModeJsonCookieTest.php b/core/tests/Drupal/FunctionalTests/Rest/EntityFormModeJsonCookieTest.php
index 5f336260e0ed..f8a1753a8777 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/EntityFormModeJsonCookieTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/EntityFormModeJsonCookieTest.php
@@ -26,4 +26,9 @@ class EntityFormModeJsonCookieTest extends EntityFormModeResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/tests/Drupal/FunctionalTests/Rest/EntityFormModeXmlAnonTest.php b/core/tests/Drupal/FunctionalTests/Rest/EntityFormModeXmlAnonTest.php
index 2da724f804a3..f5065283cc32 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/EntityFormModeXmlAnonTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/EntityFormModeXmlAnonTest.php
@@ -23,4 +23,9 @@ class EntityFormModeXmlAnonTest extends EntityFormModeResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/tests/Drupal/FunctionalTests/Rest/EntityFormModeXmlBasicAuthTest.php b/core/tests/Drupal/FunctionalTests/Rest/EntityFormModeXmlBasicAuthTest.php
index 721ded8fd959..64ce5a08311f 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/EntityFormModeXmlBasicAuthTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/EntityFormModeXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class EntityFormModeXmlBasicAuthTest extends EntityFormModeResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Rest/EntityFormModeXmlCookieTest.php b/core/tests/Drupal/FunctionalTests/Rest/EntityFormModeXmlCookieTest.php
index 6f426570a564..c02d46d58bfc 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/EntityFormModeXmlCookieTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/EntityFormModeXmlCookieTest.php
@@ -28,4 +28,9 @@ class EntityFormModeXmlCookieTest extends EntityFormModeResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/tests/Drupal/FunctionalTests/Rest/EntityViewDisplayJsonAnonTest.php b/core/tests/Drupal/FunctionalTests/Rest/EntityViewDisplayJsonAnonTest.php
index c26362aa748c..38b1c21f7a14 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/EntityViewDisplayJsonAnonTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/EntityViewDisplayJsonAnonTest.php
@@ -21,4 +21,9 @@ class EntityViewDisplayJsonAnonTest extends EntityViewDisplayResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/tests/Drupal/FunctionalTests/Rest/EntityViewDisplayJsonBasicAuthTest.php b/core/tests/Drupal/FunctionalTests/Rest/EntityViewDisplayJsonBasicAuthTest.php
index f4f2d15045c1..efd558c9f6f8 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/EntityViewDisplayJsonBasicAuthTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/EntityViewDisplayJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class EntityViewDisplayJsonBasicAuthTest extends EntityViewDisplayResourceTestBa
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Rest/EntityViewDisplayJsonCookieTest.php b/core/tests/Drupal/FunctionalTests/Rest/EntityViewDisplayJsonCookieTest.php
index 6f5832342644..90ef3a05bc4a 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/EntityViewDisplayJsonCookieTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/EntityViewDisplayJsonCookieTest.php
@@ -26,4 +26,9 @@ class EntityViewDisplayJsonCookieTest extends EntityViewDisplayResourceTestBase
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/tests/Drupal/FunctionalTests/Rest/EntityViewDisplayXmlAnonTest.php b/core/tests/Drupal/FunctionalTests/Rest/EntityViewDisplayXmlAnonTest.php
index 561f2374fd42..1ae34e3e8d9b 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/EntityViewDisplayXmlAnonTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/EntityViewDisplayXmlAnonTest.php
@@ -23,4 +23,9 @@ class EntityViewDisplayXmlAnonTest extends EntityViewDisplayResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/tests/Drupal/FunctionalTests/Rest/EntityViewDisplayXmlBasicAuthTest.php b/core/tests/Drupal/FunctionalTests/Rest/EntityViewDisplayXmlBasicAuthTest.php
index 7c7ce5bb03ab..be597c534ce5 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/EntityViewDisplayXmlBasicAuthTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/EntityViewDisplayXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class EntityViewDisplayXmlBasicAuthTest extends EntityViewDisplayResourceTestBas
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Rest/EntityViewDisplayXmlCookieTest.php b/core/tests/Drupal/FunctionalTests/Rest/EntityViewDisplayXmlCookieTest.php
index 9024ff71aedb..e3f688a670f4 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/EntityViewDisplayXmlCookieTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/EntityViewDisplayXmlCookieTest.php
@@ -28,4 +28,9 @@ class EntityViewDisplayXmlCookieTest extends EntityViewDisplayResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/tests/Drupal/FunctionalTests/Rest/EntityViewModeJsonAnonTest.php b/core/tests/Drupal/FunctionalTests/Rest/EntityViewModeJsonAnonTest.php
index 79d7e7740f1c..6d65359c916b 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/EntityViewModeJsonAnonTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/EntityViewModeJsonAnonTest.php
@@ -21,4 +21,9 @@ class EntityViewModeJsonAnonTest extends EntityViewModeResourceTestBase {
    */
   protected static $mimeType = 'application/json';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/tests/Drupal/FunctionalTests/Rest/EntityViewModeJsonBasicAuthTest.php b/core/tests/Drupal/FunctionalTests/Rest/EntityViewModeJsonBasicAuthTest.php
index e34a58c660eb..70f5271ea5fd 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/EntityViewModeJsonBasicAuthTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/EntityViewModeJsonBasicAuthTest.php
@@ -16,6 +16,11 @@ class EntityViewModeJsonBasicAuthTest extends EntityViewModeResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Rest/EntityViewModeJsonCookieTest.php b/core/tests/Drupal/FunctionalTests/Rest/EntityViewModeJsonCookieTest.php
index 5a8ac6d190a3..9c8cb402433e 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/EntityViewModeJsonCookieTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/EntityViewModeJsonCookieTest.php
@@ -26,4 +26,9 @@ class EntityViewModeJsonCookieTest extends EntityViewModeResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/tests/Drupal/FunctionalTests/Rest/EntityViewModeXmlAnonTest.php b/core/tests/Drupal/FunctionalTests/Rest/EntityViewModeXmlAnonTest.php
index 6e359484172d..a518ea3c4767 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/EntityViewModeXmlAnonTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/EntityViewModeXmlAnonTest.php
@@ -23,4 +23,9 @@ class EntityViewModeXmlAnonTest extends EntityViewModeResourceTestBase {
    */
   protected static $mimeType = 'text/xml; charset=UTF-8';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/tests/Drupal/FunctionalTests/Rest/EntityViewModeXmlBasicAuthTest.php b/core/tests/Drupal/FunctionalTests/Rest/EntityViewModeXmlBasicAuthTest.php
index 1b1e7181d0ad..510ef4dea7b7 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/EntityViewModeXmlBasicAuthTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/EntityViewModeXmlBasicAuthTest.php
@@ -18,6 +18,11 @@ class EntityViewModeXmlBasicAuthTest extends EntityViewModeResourceTestBase {
    */
   public static $modules = ['basic_auth'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Rest/EntityViewModeXmlCookieTest.php b/core/tests/Drupal/FunctionalTests/Rest/EntityViewModeXmlCookieTest.php
index bde3e24664cb..88df86e5cdcb 100644
--- a/core/tests/Drupal/FunctionalTests/Rest/EntityViewModeXmlCookieTest.php
+++ b/core/tests/Drupal/FunctionalTests/Rest/EntityViewModeXmlCookieTest.php
@@ -28,4 +28,9 @@ class EntityViewModeXmlCookieTest extends EntityViewModeResourceTestBase {
    */
   protected static $auth = 'cookie';
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
 }
diff --git a/core/tests/Drupal/FunctionalTests/Routing/CaseInsensitivePathTest.php b/core/tests/Drupal/FunctionalTests/Routing/CaseInsensitivePathTest.php
index 96b59d7be00a..a5532b24ad13 100644
--- a/core/tests/Drupal/FunctionalTests/Routing/CaseInsensitivePathTest.php
+++ b/core/tests/Drupal/FunctionalTests/Routing/CaseInsensitivePathTest.php
@@ -16,6 +16,11 @@ class CaseInsensitivePathTest extends BrowserTestBase {
    */
   public static $modules = ['system', 'views', 'node', 'system_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/tests/Drupal/FunctionalTests/Routing/DefaultFormatTest.php b/core/tests/Drupal/FunctionalTests/Routing/DefaultFormatTest.php
index 26296485e378..6a6f63f33ca8 100644
--- a/core/tests/Drupal/FunctionalTests/Routing/DefaultFormatTest.php
+++ b/core/tests/Drupal/FunctionalTests/Routing/DefaultFormatTest.php
@@ -14,6 +14,11 @@ class DefaultFormatTest extends BrowserTestBase {
    */
   public static $modules = ['system', 'default_format_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   public function testFoo() {
     $this->drupalGet('/default_format_test/human');
     $this->assertSame('format:html', $this->getSession()->getPage()->getContent());
diff --git a/core/tests/Drupal/FunctionalTests/Routing/LazyRouteProviderInstallTest.php b/core/tests/Drupal/FunctionalTests/Routing/LazyRouteProviderInstallTest.php
index cec35a07acc0..d0d9be35677e 100644
--- a/core/tests/Drupal/FunctionalTests/Routing/LazyRouteProviderInstallTest.php
+++ b/core/tests/Drupal/FunctionalTests/Routing/LazyRouteProviderInstallTest.php
@@ -14,6 +14,11 @@ class LazyRouteProviderInstallTest extends BrowserTestBase {
    */
   protected static $modules = ['lazy_route_provider_install_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests that the lazy route provider is used during a module install.
    */
diff --git a/core/tests/Drupal/FunctionalTests/Routing/PathEncodedTest.php b/core/tests/Drupal/FunctionalTests/Routing/PathEncodedTest.php
index bf33b18f3090..9962b993890e 100644
--- a/core/tests/Drupal/FunctionalTests/Routing/PathEncodedTest.php
+++ b/core/tests/Drupal/FunctionalTests/Routing/PathEncodedTest.php
@@ -21,6 +21,11 @@ class PathEncodedTest extends BrowserTestBase {
    */
   public static $modules = ['system', 'path_encoded_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   public function testGetEncoded() {
     $route_paths = [
       'path_encoded_test.colon' => '/hi/llamma:party',
diff --git a/core/tests/Drupal/FunctionalTests/Routing/RouteCachingLanguageTest.php b/core/tests/Drupal/FunctionalTests/Routing/RouteCachingLanguageTest.php
index ba4ec2bea2c3..27eab11dc78b 100644
--- a/core/tests/Drupal/FunctionalTests/Routing/RouteCachingLanguageTest.php
+++ b/core/tests/Drupal/FunctionalTests/Routing/RouteCachingLanguageTest.php
@@ -22,6 +22,11 @@ class RouteCachingLanguageTest extends BrowserTestBase {
    */
   public static $modules = ['path', 'node', 'content_translation', 'link', 'block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * An user with permissions to administer content types.
    *
diff --git a/core/tests/Drupal/FunctionalTests/Routing/RouteCachingNonPathLanguageNegotiationTest.php b/core/tests/Drupal/FunctionalTests/Routing/RouteCachingNonPathLanguageNegotiationTest.php
index 37a07c69fe56..43e5845306b4 100644
--- a/core/tests/Drupal/FunctionalTests/Routing/RouteCachingNonPathLanguageNegotiationTest.php
+++ b/core/tests/Drupal/FunctionalTests/Routing/RouteCachingNonPathLanguageNegotiationTest.php
@@ -23,6 +23,11 @@ class RouteCachingNonPathLanguageNegotiationTest extends BrowserTestBase {
    */
   public static $modules = ['language', 'block'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * The admin user.
    *
diff --git a/core/tests/Drupal/FunctionalTests/Theme/BartikTest.php b/core/tests/Drupal/FunctionalTests/Theme/BartikTest.php
index 8ef9db422999..20b2a5da81d1 100644
--- a/core/tests/Drupal/FunctionalTests/Theme/BartikTest.php
+++ b/core/tests/Drupal/FunctionalTests/Theme/BartikTest.php
@@ -14,15 +14,7 @@ class BartikTest extends BrowserTestBase {
   /**
    * {@inheritdoc}
    */
-  public function setUp() {
-    parent::setUp();
-
-    $this->assertTrue($this->container->get('theme_installer')->install(['bartik']));
-    $this->container->get('config.factory')
-      ->getEditable('system.theme')
-      ->set('default', 'bartik')
-      ->save();
-  }
+  protected $defaultTheme = 'bartik';
 
   /**
    * Tests that the Bartik theme always adds its message CSS and Classy's.
diff --git a/core/tests/Drupal/FunctionalTests/Theme/ClaroTest.php b/core/tests/Drupal/FunctionalTests/Theme/ClaroTest.php
index ad052c5c4150..a9f1d7b716e1 100644
--- a/core/tests/Drupal/FunctionalTests/Theme/ClaroTest.php
+++ b/core/tests/Drupal/FunctionalTests/Theme/ClaroTest.php
@@ -25,15 +25,7 @@ class ClaroTest extends BrowserTestBase {
   /**
    * {@inheritdoc}
    */
-  public function setUp() {
-    parent::setUp();
-
-    $this->assertTrue(\Drupal::service('theme_installer')->install(['claro']));
-    $this->container->get('config.factory')
-      ->getEditable('system.theme')
-      ->set('default', 'claro')
-      ->save();
-  }
+  protected $defaultTheme = 'claro';
 
   /**
    * Tests that the Claro theme always adds its elements.css.
diff --git a/core/tests/Drupal/FunctionalTests/Theme/ClassyTest.php b/core/tests/Drupal/FunctionalTests/Theme/ClassyTest.php
index dca624e4e689..9aabc6167180 100644
--- a/core/tests/Drupal/FunctionalTests/Theme/ClassyTest.php
+++ b/core/tests/Drupal/FunctionalTests/Theme/ClassyTest.php
@@ -14,15 +14,7 @@ class ClassyTest extends BrowserTestBase {
   /**
    * {@inheritdoc}
    */
-  public function setUp() {
-    parent::setUp();
-
-    $this->assertTrue($this->container->get('theme_installer')->install(['classy']));
-    $this->container->get('config.factory')
-      ->getEditable('system.theme')
-      ->set('default', 'classy')
-      ->save();
-  }
+  protected $defaultTheme = 'classy';
 
   /**
    * Tests that the Classy theme always adds its message CSS.
diff --git a/core/tests/Drupal/FunctionalTests/UserHelpersTest.php b/core/tests/Drupal/FunctionalTests/UserHelpersTest.php
index 074f11e3f19b..ad053e362a21 100644
--- a/core/tests/Drupal/FunctionalTests/UserHelpersTest.php
+++ b/core/tests/Drupal/FunctionalTests/UserHelpersTest.php
@@ -11,6 +11,11 @@
  */
 class UserHelpersTest extends BrowserTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Tests WebTestBase::drupalUserIsLoggedIn().
    */
diff --git a/core/tests/Drupal/Tests/Listeners/DeprecationListenerTrait.php b/core/tests/Drupal/Tests/Listeners/DeprecationListenerTrait.php
index de82e6583974..05ec56c59598 100644
--- a/core/tests/Drupal/Tests/Listeners/DeprecationListenerTrait.php
+++ b/core/tests/Drupal/Tests/Listeners/DeprecationListenerTrait.php
@@ -187,8 +187,6 @@ public static function getSkippedDeprecations() {
       'Using the "Symfony\Component\Validator\Constraints\Length" constraint with the "min" option without setting the "allowEmptyString" one is deprecated and defaults to true. In 5.0, it will become optional and default to false.',
       'The "core/jquery.ui.checkboxradio" asset library is deprecated in drupal:8.8.0 and is removed from drupal:9.0.0. See https://www.drupal.org/node/3067969',
       'The "core/jquery.ui.controlgroup" asset library is deprecated in drupal:8.8.0 and is removed from drupal:9.0.0. See https://www.drupal.org/node/3067969',
-      // @todo Remove in https://www.drupal.org/project/drupal/issues/3082655
-      'Drupal\Tests\BrowserTestBase::$defaultTheme is required in drupal:9.0.0 when using an install profile that does not set a default theme. See https://www.drupal.org/node/2352949, which includes recommendations on which theme to use.',
       // The following deprecation is listed for Twig 2 compatibility when unit
       // testing using \Symfony\Component\ErrorHandler\DebugClassLoader.
       'The "Twig\Environment::getTemplateClass()" method is considered internal. It may change without further notice. You should not extend it from "Drupal\Core\Template\TwigEnvironment".',
-- 
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