def test_loseConnection(self):
        """
        Verify that a protocol connected to L{StandardIO} can disconnect
        itself using C{transport.loseConnection}.
        """
        errorLogFile = self.mktemp()
        log.msg("Child process logging to " + errorLogFile)
        p = StandardIOTestProcessProtocol()
        d = p.onCompletion
        self._spawnProcess(p, b'stdio_test_loseconn', errorLogFile)

        def processEnded(reason):
            # Copy the child's log to ours so it's more visible.
            with open(errorLogFile, 'r') as f:
                for line in f:
                    log.msg("Child logged: " + line.rstrip())

            self.failIfIn(1, p.data)
            reason.trap(error.ProcessDone)
        return self._requireFailure(d, processEnded)

        Verify that a protocol connected to L{StandardIO} can disconnect
        itself using C{transport.loseConnection}.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_stdio.py