Fatal error: Uncaught Error: Class "Drupal\Tests\field\Kernel\FieldKernelTestBase" not found in /home/www/drupal8/test/core/modules/field/tests/src/Kernel/String/UuidItemTest.php:14
Stack trace:
#0 {main}
thrown in /home/www/drupal8/test/core/modules/field/tests/src/Kernel/String/UuidItemTest.php on line 14