6 files declare their use of FileMigrationTestTrait in Drupal 8

MigrateImageTest.php in core/modules/image/tests/src/Kernel/Migrate/d6/MigrateImageTest.php

MigrateNodeCompleteTest.php in core/modules/node/tests/src/Kernel/Migrate/d6/MigrateNodeCompleteTest.php

MigrateNodeTest.php in core/modules/node/tests/src/Kernel/Migrate/d6/MigrateNodeTest.php

MigrateUserPictureD6FileTest.php in core/modules/user/tests/src/Kernel/Migrate/d6/MigrateUserPictureD6FileTest.php

MigrateUserPictureFileTest.php in core/modules/user/tests/src/Kernel/Migrate/d6/MigrateUserPictureFileTest.php

MigrateUserTest.php in core/modules/user/tests/src/Kernel/Migrate/d6/MigrateUserTest.php