Fatal error: Uncaught Error: Class "Drupal\Tests\views_ui\Functional\UITestBase" not found in /home/www/drupal8/test/core/modules/views_ui/tests/src/Functional/ArgumentValidatorTest.php:12 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/views_ui/tests/src/Functional/ArgumentValidatorTest.php on line 12