def verify_response_time(self, expected_below):
        """
        Verify that response time (time span between request-response) is reasonable.

        :param expected_below: integer
        :return: Nothing
        :raises: ValueError if timedelta > expected time
        """
        if self.timedelta > expected_below:
            raise ValueError("Response time is more (%f) than expected (%f)!"
                             % (self.timedelta, expected_below))