Fatal error: Uncaught Error: Class "Drupal\Tests\system\FunctionalJavascript\OffCanvasTestBase" not found in /home/www/drupal8/test/core/modules/system/tests/src/FunctionalJavascript/OffCanvasTest.php:10 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/system/tests/src/FunctionalJavascript/OffCanvasTest.php on line 10