diff --git a/core/modules/responsive_image/src/FunctionalJavascript/ResponsiveImageFieldUiTest.php b/core/modules/responsive_image/tests/src/FunctionalJavascript/ResponsiveImageFieldUiTest.php
similarity index 97%
rename from core/modules/responsive_image/src/FunctionalJavascript/ResponsiveImageFieldUiTest.php
rename to core/modules/responsive_image/tests/src/FunctionalJavascript/ResponsiveImageFieldUiTest.php
index 26571f556e98ed25a12043803df2e2bac640995c..7ecfd5fbec38f3b45a013115d01ca64a2f2eff39 100644
--- a/core/modules/responsive_image/src/FunctionalJavascript/ResponsiveImageFieldUiTest.php
+++ b/core/modules/responsive_image/tests/src/FunctionalJavascript/ResponsiveImageFieldUiTest.php
@@ -1,6 +1,6 @@
 <?php
 
-namespace Drupal\responsive_image\Tests;
+namespace Drupal\Tests\responsive_image\FunctionalJavascript;
 
 use Drupal\FunctionalJavascriptTests\WebDriverTestBase;
 use Drupal\responsive_image\Entity\ResponsiveImageStyle;
@@ -12,6 +12,11 @@
  */
 class ResponsiveImageFieldUiTest extends WebDriverTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * Modules to install.
    *