Fatal error: Uncaught Error: Class "PHPUnit\Framework\TestCase" not found in /home/www/drupal8/test/core/tests/Drupal/Tests/Component/Serialization/YamlTest.php:16
Stack trace:
#0 {main}
thrown in /home/www/drupal8/test/core/tests/Drupal/Tests/Component/Serialization/YamlTest.php on line 16