Is this function needed? Not sure if it's for backwards compatibility or not. ``TropoTest`` extends from ``RapidTest``, which has a ``router`` [class attribute](https://github.com/rapidsms/rapidsms/blob/develop/rapidsms/tests/harness/router.py#L115) (looks like this should be added to the RapidSMS docs). I think the tests could just call ``self.router.backends[BACKEND_NAME]``.