'msg_queue ~ Provider.notify(msg) ~ Publisher.publish(msg)'

def test_publisher_shall_append_subscription_message_to_queue(cls):

    expected_msg = 'expected    msg'
    pro = Provider()
    pub = Publisher(pro)
    sub = Subscriber('sub    name', pro)
    cls.assertEqual(len(pro.msg_queue), 0)
    pub.publish(expected_msg)
    cls.assertEqual(len(pro.msg_queue), 1)
    cls.assertEqual(pro.msg_queue[0], expected_msg)
