Random failure in ImageTest::testAltTextRequired

I keep forgetting that core/drupalci.yml drives not PHPUnit, but core/scripts/run-tests.sh 😬

PHP Fatal error:  Uncaught ReflectionException: Class "Drupal\Tests\ckeditor5\FunctionalJavascript\ImageTest::testAltTextRequired" does not exist in /var/www/html/core/lib/Drupal/Core/Test/TestDiscovery.php:316

… despite

  --class     Run tests identified by specific class names, instead of group names.
              A specific test method can be added, for example,
              'Drupal\book\Tests\BookTest::testBookExport'. This argument must
              be last on the command line.

in the docs 🤷‍♀️

Created #3317504: run-tests.sh claims to support running a particular test method, but does not for that…

Alright, so instead of running only the one randomly failing test method, due to lacking infrastructure we'll just have to run all of them 🫥

Reproduced locally.

This is a race condition caused by

    $this->addImage();
    $this->assertNotEmpty($assert_session->waitForElementVisible('css', '.ck-widget.image'));

The first uploads an image using \Behat\Mink\Element\NodeElement::attachFile() but doesn't wait for the upload to complete, instead it waits for .ck-widget.image … but this is the THIRD image, so it always matches instantaneously.

core/modules/ckeditor5/js/ckeditor5_plugins/drupalImage/src/imageupload/drupalimageuploadadapter.js uses an AJAX request, we should wait for that … except that it doesn't use the AJAX system. Fortunately, there are other things we can wait for 👍