'Verify that registering a non-streaming producer invokes its
resumeProducing() method and that you can only register one producer
at a time.'

def test_doubleProducer(self):

    fd = abstract.FileDescriptor()
    fd.connected = 1
    dp = DummyProducer()
    fd.registerProducer(dp, 0)
    self.assertEqual(dp.events, ['resume'])
    self.assertRaises(RuntimeError, fd.registerProducer, DummyProducer(), 0)
