Fatal error: Uncaught Error: Class "Drupal\KernelTests\Core\Plugin\PluginTestBase" not found in /home/www/drupal8/test/core/tests/Drupal/KernelTests/Core/Plugin/InspectionTest.php:10 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/tests/Drupal/KernelTests/Core/Plugin/InspectionTest.php on line 10