Fatal error: Uncaught Error: Class "Drupal\Tests\block\Functional\BlockTestBase" not found in /home/www/drupal8/test/core/modules/block/tests/src/Functional/BlockTest.php:16 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/block/tests/src/Functional/BlockTest.php on line 16