Fatal error: Uncaught Error: Interface "Drupal\Core\Cache\Context\CacheContextInterface" not found in /home/www/drupal8/test/core/modules/simpletest/src/Cache/Context/TestDiscoveryCacheContext.php:16 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/simpletest/src/Cache/Context/TestDiscoveryCacheContext.php on line 16