Fatal error: Uncaught Error: Class "Drupal\KernelTests\KernelTestBase" not found in /home/www/drupal8/test/modules/webform/tests/src/Kernel/Entity/WebformEntityTest.php:17
Stack trace:
#0 {main}
thrown in /home/www/drupal8/test/modules/webform/tests/src/Kernel/Entity/WebformEntityTest.php on line 17