Fatal error: Uncaught Error: Class "Drupal\KernelTests\Core\Entity\EntityKernelTestBase" not found in /home/www/drupal8/test/core/modules/comment/tests/src/Kernel/CommentValidationTest.php:15 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/comment/tests/src/Kernel/CommentValidationTest.php on line 15