def METHOD_NAME(self, Popen):
    manager = ListenerManager()
    backend = Backend.objects.create(name="foo")
    # start existing backends
    manager.keep_listeners_running()
    manager.stop = MagicMock()
    manager.start = MagicMock()
    # backend is changed
    backend.name = 'bar'
    backend.save()
    manager.keep_listeners_running()
    manager.stop.assert_called_with(backend.id)
    manager.start.assert_called_with(backend)