Fatal error: Uncaught Error: Class "Drupal\Tests\user\Unit\Plugin\Action\RoleUserTestBase" not found in /home/www/drupal8/test/core/modules/user/tests/src/Unit/Plugin/Action/AddRoleUserTest.php:11 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/user/tests/src/Unit/Plugin/Action/AddRoleUserTest.php on line 11