I made this trivial GrowthExperiments patch: https://gerrit.wikimedia.org/r/c/mediawiki/extensions/GrowthExperiments/+/779082
It fails in quibble-vendor-mysql-php74-noselenium-docker, and the failing lines are probably these:
14:42:15 There were 2 failures: 14:42:15 14:42:15 1) ParserIntegrationTest::testParse with data set "timedMediaHandlerParserTests.txt: Video with different thumb image" ('legacy parser') 14:42:15 Failed asserting that two strings are equal. 14:42:15 --- Expected 14:42:15 +++ Actual 14:42:15 @@ @@ 14:42:15 -'<figure class="mw-default-size" typeof="mw:Video/Thumb"><a href="/wiki/File:Video.ogv" title="File:Video.ogv"><img alt="Video.ogv" src="http://example.com/images/3/3a/Foobar.jpg" decoding="async" width="1941" height="220" /></a><figcaption></figcaption></figure>' 14:42:15 +'<figure class="mw-default-size" typeof="mw:Image/Thumb"><a href="/wiki/File:Video.ogv" title="File:Video.ogv"><img alt="Video.ogv" src="http://example.com/images/3/3a/Foobar.jpg" decoding="async" width="1941" height="220" /></a><figcaption></figcaption></figure>' 14:42:15 14:42:15 /workspace/src/tests/phpunit/suites/ParserIntegrationTest.php:64 14:42:15 /workspace/src/tests/phpunit/suites/SuiteEventsTrait.php:69 14:42:15 /workspace/src/tests/phpunit/suites/SuiteEventsTrait.php:69 14:42:15 === Logs generated by test case 14:42:15 [wfDebug] [debug] ParserTestRunner::runTest: running Video with different thumb image {"private":false} 14:42:15 [wfDebug] [debug] ParserFactory: using default preprocessor {"private":false} 14:42:15 [wfDebug] [debug] File::transform: Doing stat for mwstore://local-backend/local-thumb/3/3a/Foobar.jpg/1941px-Foobar.jpg {"private":false} 14:42:15 [wfDebug] [debug] MockImageHandler::doFakeTransform: returning unscaled image {"private":false} 14:42:15 [wfDebug] [debug] ContextSource::getContext (FormatMetadata): called and $context is null. Using RequestContext::getMain() {"private":false} 14:42:15 === 14:42:15 14:42:15 2) ParserIntegrationTest::testParse with data set "timedMediaHandlerParserTests.txt: Image with video thumb" ('legacy parser') 14:42:15 Failed asserting that two strings are equal. 14:42:15 --- Expected 14:42:15 +++ Actual 14:42:15 @@ @@ 14:42:15 -'<figure class="mw-default-size" typeof="mw:Image/Thumb"><span><video id="mwe_player_1" poster="http://example.com/images/thumb/0/00/Video.ogv/320px--Video.ogv.jpg" controls="" preload="none" width="320" height="240" data-durationhint="5" data-mwtitle="Video.ogv" data-mwprovider="local"><source src="http://example.com/images/0/00/Video.ogv" type="video/ogg; codecs="theora"" data-title="Original Ogg file, 320 × 240 (590 kbps)" data-shorttitle="Ogg source" data-width="320" data-height="240" data-bandwidth="590013" data-framerate="30" /></video></span><figcaption></figcaption></figure>' 14:42:15 +'<figure class="mw-default-size" typeof="mw:Video/Thumb"><span><video id="mwe_player_1" poster="http://example.com/images/thumb/0/00/Video.ogv/320px--Video.ogv.jpg" controls="" preload="none" width="320" height="240" data-durationhint="5" data-mwtitle="Video.ogv" data-mwprovider="local"><source src="http://example.com/images/0/00/Video.ogv" type="video/ogg; codecs="theora"" data-title="Original Ogg file, 320 × 240 (590 kbps)" data-shorttitle="Ogg source" data-width="320" data-height="240" data-bandwidth="590013" data-framerate="30" /></video></span><figcaption></figcaption></figure>' 14:42:15 14:42:15 /workspace/src/tests/phpunit/suites/ParserIntegrationTest.php:64 14:42:15 /workspace/src/tests/phpunit/suites/SuiteEventsTrait.php:69 14:42:15 /workspace/src/tests/phpunit/suites/SuiteEventsTrait.php:69
(Please fix my tags if needed. I don't often report bugs like this one. Thank you.)