def METHOD_NAME(self):
    self.transport._sub_id = None
    f = concurrent.Future()
    f.set_result(None)
    self.mock_nats_client.unsubscribe.return_value = f
    self.mock_nats_client.flush.return_value = f
    yield self.transport.close()
    self.mock_nats_client.unsubscribe.assert_not_called()