'If there is no producer, the L{HTTPChannel} can still have
C{unregisterProducer} called.'

def test_HTTPChannelCanUnregisterWithNoProducer(self):

    (channel, transport) = self.buildChannelAndTransport(StringTransport(), DummyHTTPHandler)
    channel.unregisterProducer()
    self.assertIs(channel._requestProducer, None)
