def test_connectionLost(self):
        """
        The L{IProtocol} provider passed to L{Response.deliverBody} has its
        C{connectionLost} method called with a L{Failure} wrapping
        L{ResponseDone} when the response's C{_bodyDataFinished} method is
        called.
        """
        lost = []
        class ListConsumer(Protocol):
            def connectionLost(self, reason):
                lost.append(reason)

        consumer = ListConsumer()
        response = justTransportResponse(StringTransport())
        response.deliverBody(consumer)

        response._bodyDataFinished()
        lost[0].trap(ResponseDone)
        self.assertEqual(len(lost), 1)

        # The protocol reference should be dropped, too, to facilitate GC or
        # whatever.
        self.assertIdentical(response._bodyProtocol, None)

        The L{IProtocol} provider passed to L{Response.deliverBody} has its
        C{connectionLost} method called with a L{Failure} wrapping
        L{ResponseDone} when the response's C{_bodyDataFinished} method is
        called.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/test/test_newclient.py