Fatal error: Uncaught Error: Class "Drupal\FunctionalJavascriptTests\WebDriverTestBase" not found in /home/www/drupal8/test/core/modules/system/tests/src/FunctionalJavascript/Form/RebuildTest.php:17
Stack trace:
#0 {main}
thrown in /home/www/drupal8/test/core/modules/system/tests/src/FunctionalJavascript/Form/RebuildTest.php on line 17