6 files declare their use of OEmbedTestTrait in Drupal 8

MediaSourceOEmbedVideoTest.php in core/modules/media/tests/src/FunctionalJavascript/MediaSourceOEmbedVideoTest.php

MediaStandardProfileTest.php in core/modules/media/tests/src/FunctionalJavascript/MediaStandardProfileTest.php

OEmbedFormatterTest.php in core/modules/media/tests/src/Functional/FieldFormatter/OEmbedFormatterTest.php

ResourceFetcherTest.php in core/modules/media/tests/src/Functional/ResourceFetcherTest.php

UrlResolverTest.php in core/modules/media/tests/src/Functional/UrlResolverTest.php

WidgetOEmbedTest.php in core/modules/media_library/tests/src/FunctionalJavascript/WidgetOEmbedTest.php