Fatal error: Uncaught Error: Class "Drupal\Tests\Core\Plugin\LazyPluginCollectionTestBase" not found in /home/www/drupal8/test/core/tests/Drupal/Tests/Core/Plugin/DefaultSingleLazyPluginCollectionTest.php:13 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/tests/Drupal/Tests/Core/Plugin/DefaultSingleLazyPluginCollectionTest.php on line 13