'"Test the subscription.'

@patch('homeassistant.components.mqtt.async_subscribe')
def test_subscribe(self, mock_sub):

    sub_topic = 'foo'
    assert self.add_eventstream(sub_topic=sub_topic)
    self.hass.block_till_done()
    mock_sub.assert_called_with(self.hass, sub_topic, ANY)
