Make DrupalCI discover and run JSON:API Hypermedia's tests

https://git.drupalcode.org/project/jsonapi_hypermedia/commit/6f9d50b caught my eye.

https://www.drupal.org/pift-ci-job/1407402 is indeed failing. This is what's happening:

00:03:08.824 cd /var/www/html && sudo MINK_DRIVER_ARGS_WEBDRIVER='["chrome", {"browserName":"chrome","chromeOptions":{"args":["--disable-gpu","--headless"]}}, "http://chromedriver-jenkins-drupal-contrib-44119:9515"]' -u www-data php /var/www/html/core/scripts/run-tests.sh --color --keep-results --suppress-deprecations --types "Simpletest,PHPUnit-Unit,PHPUnit-Kernel,PHPUnit-Functional" --concurrency "32" --repeat "1" --sqlite "/var/lib/drupalci/workdir/run_tests.standard/simpletest.sqlite" --dburl "mysql://drupaltestbot:drupaltestbotpw@172.18.0.4/jenkins_drupal_contrib_44119" --url "http://php-apache-jenkins-drupal-contrib-44119/subdirectory" --directory modules/contrib/jsonapi_hypermedia
00:03:09.153   ERROR: No valid tests were specified.

That error message originates from run-tests.sh. Running it locally yields the same result:

wim.leers at Acquia in ~/Work/d8 on 8.8.x*
$ php core/scripts/run-tests.sh --directory modules/jsonapi_hypermedia
  ERROR: No valid tests were specified.

So I enabled xdebug and stepped through it.

The root cause:

        // Extract all class names.
        // Abstract classes are excluded on purpose.
        preg_match_all('@^\s*class ([^ ]+)@m', $content, $matches);
        if (!$namespace) {
          $test_list = array_merge($test_list, $matches[1]);
        }

in run-tests.sh does not only filter out abstract test classes, but also final test classes… 🤦‍♂️🤯 And this has been known for a long time: #2913819: run-tests.sh ignores final classes. Surprisingly, zero follow-up on that issue. #2551981: Add --directory option to run-tests.sh test discovery introduced this bug.