Fatal error: Uncaught Error: Class "Drupal\KernelTests\KernelTestBase" not found in /home/qcsvlel/www/core/modules/block_content/tests/src/Kernel/BlockContentEntityReferenceSelectionTest.php:19 Stack trace: #0 {main} thrown in /home/qcsvlel/www/core/modules/block_content/tests/src/Kernel/BlockContentEntityReferenceSelectionTest.php on line 19