Mock Twilio

test_twilio.py

@patch('twilio.rest.resources.SmsMessages')
def test_send_sms_valid_args(self, MockClass):
    instance = MockClass.return_value
    instance.create.return_value = None
    to_number = 5555555555
    msg = 'Hello world'
    send_sms(to_number, msg)

    instance.create.assert_called_once_with(to='+1' + str(to_number),
                                body=msg, from_=settings.TWILIO_FROM_NUM)