diff --git a/core/modules/system/src/Tests/Asset/LibraryDiscoveryIntegrationTest.php b/core/modules/system/src/Tests/Asset/LibraryDiscoveryIntegrationTest.php
index f433390..f109d4c 100644
--- a/core/modules/system/src/Tests/Asset/LibraryDiscoveryIntegrationTest.php
+++ b/core/modules/system/src/Tests/Asset/LibraryDiscoveryIntegrationTest.php
@@ -159,19 +159,19 @@ public function testLibrariesOverrideOtherAssetLibraryNames() {
 
     // Assert Drupal relative paths.
     $library = $library_discovery->getLibraryByName('core', 'jquery.once'); 
-    $this->assertAssetInLibrary($library['js'], 'jquery.once', 'themes/my_theme/js/jquery.once.js');
+    $this->assertAssetInLibrary($library['css'], 'drupal.dropbutton', 'themes/my_theme/css/dropbutton.css');
 
     // Assert streamwrappers.
     $library = $library_discovery->getLibraryByName('core', 'drupal.active-link'); 
-    $this->assertAssetInLibrary($library['js'], 'drupal.active-link', 'public://my_js/active-link.js');
+    $this->assertAssetInLibrary($library['css'], 'drupal.vertical-tabs', 'public://my_css/vertical-tabs.css');
 
     // Assert protocol-free URI.
     $library = $library_discovery->getLibraryByName('core', 'drupal.dialog'); 
-    $this->assertAssetInLibrary($library['js'], 'drupal.dialog', '//my-server/my_theme/js/dialog.js');
+    $this->assertAssetInLibrary($library['css'], 'jquery.ui', '//my-server/my_theme/css/jquery_ui.css');
 
     // Assert regular URI.
     $library = $library_discovery->getLibraryByName('core', 'jquery.farbtastic'); 
-    $this->assertAssetInLibrary($library['js'], 'jquery.farbtastic', 'http://example.com/my_theme/js/farbtastic.js');
+    $this->assertAssetInLibrary($library['css'], 'jquery.farbtastic', 'http://example.com/my_theme/css/farbtastic.css');
   }
 
   /**
diff --git a/core/modules/system/tests/themes/test_theme/test_theme.info.yml b/core/modules/system/tests/themes/test_theme/test_theme.info.yml
index 32d723c..ae8a09c 100644
--- a/core/modules/system/tests/themes/test_theme/test_theme.info.yml
+++ b/core/modules/system/tests/themes/test_theme/test_theme.info.yml
@@ -28,13 +28,13 @@ libraries-override:
   # It works for JS as well.
   core/jquery/js/assets/vendor/jquery/jquery.min.js: js/collapse.js
   # Use Drupal relative paths.
-  core/jquery.once/js/assets/vendor/jquery-once/jquery.once.min.js: /themes/my_theme/js/jquery.once.js
+  core/drupal.dropbutton/css/component/misc/dropbutton/dropbutton.css: /themes/my_theme/css/dropbutton.css
   # Use streamwrappers.
-  core/drupal.active-link/js/misc/active-link.js: public://my_js/active-link.js
+  core/drupal.vertical-tabs/css/component/misc/vertical-tabs.css: public://my_css/vertical-tabs.css
   # Use protocol-free URI.
-  core/drupal.dialog/js/misc/dialog/dialog.js: //my-server/my_theme/js/dialog.js
+  core/jquery.ui/css/component/assets/vendor/jquery.ui/themes/base/core.css: //my-server/my_theme/css/jquery_ui.css
   # Use regular URI.
-  core/jquery.farbtastic/js/component/assets/vendor/farbtastic/farbtastic.js: http://example.com/my_theme/js/farbtastic.js
+  core/jquery.farbtastic/css/component/assets/vendor/farbtastic/farbtastic.css: http://example.com/my_theme/css/farbtastic.css
 regions:
   content: Content
   left: Left