def METHOD_NAME(self, mock_load):
    """
    Assert that dev-mode falls back to file locking.
    """
    lockfile = Path(settings.SELF_CERTIFI_DIR) / ".lock"
    def assert_lock_file(*args, **kwargs):
        self.assertTrue(lockfile.is_file())
    mock_load.side_effect = assert_lock_file
    with patch("openforms.setup.get_redis_connection") as mock_redis_conn:
        mock_redis_conn.return_value.ping.side_effect = redis.ConnectionError
        load_self_signed_certs()
    mock_load.assert_called_once_with(settings.SELF_CERTIFI_DIR)