'L{IReactorTCP.listenTCP} returns an object which provides
L{IListeningPort}.'

def test_listen(self):

    f = MyServerFactory()
    p1 = reactor.listenTCP(0, f, interface='127.0.0.1')
    self.addCleanup(p1.stopListening)
    self.assertTrue(interfaces.IListeningPort.providedBy(p1))
