diff --git a/core/modules/settings_tray/tests/src/FunctionalJavascript/SettingsTrayBlockFormTest.php b/core/modules/settings_tray/tests/src/FunctionalJavascript/SettingsTrayBlockFormTest.php
index d505a0befcb33e1d05b4dec5c8853cd7dd9c7b57..a5db109f34c65577c41c37ab3c83b4879f7387f9 100644
--- a/core/modules/settings_tray/tests/src/FunctionalJavascript/SettingsTrayBlockFormTest.php
+++ b/core/modules/settings_tray/tests/src/FunctionalJavascript/SettingsTrayBlockFormTest.php
@@ -9,6 +9,7 @@
 /**
  * Testing opening and saving block forms in the off-canvas dialog.
  *
+ * @group #slow
  * @group settings_tray
  */
 class SettingsTrayBlockFormTest extends SettingsTrayTestBase {
diff --git a/core/modules/simpletest/tests/src/Functional/SimpletestUiTest.php b/core/modules/simpletest/tests/src/Functional/SimpletestUiTest.php
index 048ed2738949c46b4cabb04698ad66c585cf096a..f91cb6d5077dc6cf229445d0a70e328d029c44b2 100644
--- a/core/modules/simpletest/tests/src/Functional/SimpletestUiTest.php
+++ b/core/modules/simpletest/tests/src/Functional/SimpletestUiTest.php
@@ -10,6 +10,7 @@
 /**
  * Test various aspects of testing through the UI form.
  *
+ * @group #slow
  * @group simpletest
  */
 class SimpletestUiTest extends BrowserTestBase {
diff --git a/core/modules/system/tests/src/Functional/Module/InstallUninstallTest.php b/core/modules/system/tests/src/Functional/Module/InstallUninstallTest.php
index 9ca44078012f912e095e985a7eee411f520ff0e2..d1f6be457f0dc98a9a56a767ceac5aef390893b8 100644
--- a/core/modules/system/tests/src/Functional/Module/InstallUninstallTest.php
+++ b/core/modules/system/tests/src/Functional/Module/InstallUninstallTest.php
@@ -9,6 +9,7 @@
 /**
  * Install/uninstall core module and confirm table creation/deletion.
  *
+ * @group #slow
  * @group Module
  */
 class InstallUninstallTest extends ModuleTestBase {
diff --git a/core/modules/system/tests/src/Functional/Update/UpdatePathTestBaseFilledTest.php b/core/modules/system/tests/src/Functional/Update/UpdatePathTestBaseFilledTest.php
index 84b44df54791dfb8e9fc3f0c6cbbd5ab1df85d63..5cc23b007d6593208d370be3b7ee18c0e621c1ff 100644
--- a/core/modules/system/tests/src/Functional/Update/UpdatePathTestBaseFilledTest.php
+++ b/core/modules/system/tests/src/Functional/Update/UpdatePathTestBaseFilledTest.php
@@ -10,6 +10,7 @@
 /**
  * Runs UpdatePathTestBaseTest with a dump filled with content.
  *
+ * @group #slow
  * @group Update
  * @group legacy
  */
diff --git a/core/modules/workspaces/tests/src/Kernel/WorkspaceIntegrationTest.php b/core/modules/workspaces/tests/src/Kernel/WorkspaceIntegrationTest.php
index 2678d899904c84659ac97907b39a71ac15852d5b..160c0050575dbc40122058a616817ae95f7f81ae 100644
--- a/core/modules/workspaces/tests/src/Kernel/WorkspaceIntegrationTest.php
+++ b/core/modules/workspaces/tests/src/Kernel/WorkspaceIntegrationTest.php
@@ -18,6 +18,7 @@
 /**
  * Tests a complete deployment scenario across different workspaces.
  *
+ * @group #slow
  * @group workspaces
  */
 class WorkspaceIntegrationTest extends KernelTestBase {
diff --git a/core/tests/Drupal/KernelTests/Core/Extension/ModuleConfigureRouteTest.php b/core/tests/Drupal/KernelTests/Core/Extension/ModuleConfigureRouteTest.php
index 96e469a84bbdfecd4fd57c956f4c72706e652f59..0fca6d2e6ecfdfa9bf4c2dcb5d786e5957f91a84 100644
--- a/core/tests/Drupal/KernelTests/Core/Extension/ModuleConfigureRouteTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Extension/ModuleConfigureRouteTest.php
@@ -8,6 +8,7 @@
 /**
  * Tests the configure route for core modules.
  *
+ * @group #slow
  * @group Module
  */
 class ModuleConfigureRouteTest extends KernelTestBase {