Fatal error: Uncaught Error: Class "Drupal\Tests\WebAssert" not found in /home/www/drupal8/test/core/tests/Drupal/FunctionalJavascriptTests/JSWebAssert.php:14 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/tests/Drupal/FunctionalJavascriptTests/JSWebAssert.php on line 14