Fatal error: Uncaught Error: Class "Drupal\Tests\UnitTestCase" not found in /home/qcsvlel/www/core/modules/file/tests/src/Unit/Plugin/migrate/field/d6/FileFieldTest.php:19 Stack trace: #0 {main} thrown in /home/qcsvlel/www/core/modules/file/tests/src/Unit/Plugin/migrate/field/d6/FileFieldTest.php on line 19