Move the helpful method to the TestCase class

apps/encryption/tests/lib/HookManagerTest.php

apps/encryption/tests/lib/KeyManagerTest.php

apps/encryption/tests/lib/MigrationTest.php

apps/encryption/tests/lib/RecoveryTest.php

apps/encryption/tests/lib/crypto/cryptTest.php

apps/encryption/tests/lib/crypto/encryptionTest.php

apps/files_sharing/tests/external/managertest.php

...files_sharing/tests/middleware/sharingcheckmiddleware.php

tests/core/command/encryption/disabletest.php

tests/core/command/encryption/enabletest.php

tests/core/command/encryption/setdefaultmoduletest.php

tests/core/command/user/deletetest.php

tests/core/command/user/lastseentest.php

tests/lib/activitymanager.php

tests/lib/appframework/http/RequestTest.php

tests/lib/encryption/keys/storage.php

tests/lib/encryption/managertest.php

tests/lib/files/pathverificationtest.php

tests/lib/files/storage/wrapper/encryption.php

tests/lib/helper.php