[random test failure] \Drupal\Tests\ckeditor5\FunctionalJavascript\MediaTest::testViewMode random fail

Let's first proof that running \Drupal\Tests\ckeditor5\FunctionalJavascript\MediaTest::testViewMode() produces both random test failures.

Here's a patch that runs only \Drupal\Tests\ckeditor5\FunctionalJavascript\MediaTest::testViewMode() 500 times.
Let's test that patch enough times to get a feeling on what the failure rate for both of them is.

Let's first proof that running \Drupal\Tests\ckeditor5\FunctionalJavascript\MediaTest::testViewMode() and \Drupal\Tests\ckeditor5\FunctionalJavascript\MediaTest::testViewMode() alone produces both random test failures.

Here's a patch that runs only \Drupal\Tests\ckeditor5\FunctionalJavascript\MediaTest::testViewMode() 500 times.

The normal routine to prove a random failure is fixed is to run the failing patch and the patch with the fix at the same time, whilst the latter has to have ~8000 - 10.000 failure free runs to prove it's credibility.

12 * 750 = 9000 failure free runs. Also, since testViewMode is fed by a dataProvider with 2 cases, the actual method is run twice in each run.

Here's the actual patch.

LGTM

Committed/pushed to 11.x and cherry-picked back through to 9.5.x, thanks!

Automatically closed - issue fixed for 2 weeks with no activity.