def test_connectionLostAfterForceClose(self):
        """
        If a timed out transport doesn't close after 15 seconds, the
        L{HTTPChannel} will forcibly close it.
        """
        reactor, conn, transport = self.prepareAbortTest()

        # Force the follow-on forced closure.
        reactor.advance(15)
        self.assertTrue(transport.disconnecting)
        self.assertTrue(transport.disconnected)

        # Now call connectionLost on the protocol. This is done by some
        # transports, including TCP and TLS. We don't have anything we can
        # assert on here: this just must not explode.
        conn.connectionLost(error.ConnectionDone)

        If a timed out transport doesn't close after 15 seconds, the
        L{HTTPChannel} will forcibly close it.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/test/test_http2.py