def METHOD_NAME(self, source_app, app_storage):
    # Given a source in the DB
    passphrase = PassphraseGenerator.get_default().generate_passphrase()
    create_source_user(
        db_session=db.session,
        source_passphrase=passphrase,
        source_app_storage=app_storage,
    )
    # When trying to create another with the same passphrase, it fails
    with pytest.raises(SourcePassphraseCollisionError):
        create_source_user(
            db_session=db.session,
            source_passphrase=passphrase,
            source_app_storage=app_storage,
        )