'_next_channel_number must return lowest available channel number'

def test_next_channel_number_returns_lowest_unused(self):

    for channel_num in xrange(1, 50):
        self.connection._channels[channel_num] = True
    expectation = random.randint(5, 49)
    del self.connection._channels[expectation]
    self.assertEqual(self.connection._next_channel_number(), expectation)
