def test_killExitedButNotDetected(self):
        """
        L{process.Process.signalProcess} raises L{error.ProcessExitedAlready}
        if the process has exited but that twisted hasn't seen it (for example,
        if the process has been waited outside of twisted): C{os.kill} then
        raise C{OSError} with C{errno.ESRCH} as errno.
        """
        self.mockos.child = False
        self.mockos.waitChild = (0, 0)
        cmd = b'/mock/ouch'
        p = TrivialProcessProtocol(None)
        proc = reactor.spawnProcess(p, cmd, [b'ouch'], env=None, usePTY=False)
        self.mockos.raiseKill = OSError(errno.ESRCH, "Not found")
        self.assertRaises(error.ProcessExitedAlready,
                          proc.signalProcess, "KILL")

        L{process.Process.signalProcess} raises L{error.ProcessExitedAlready}
        if the process has exited but that twisted hasn't seen it (for example,
        if the process has been waited outside of twisted): C{os.kill} then
        raise C{OSError} with C{errno.ESRCH} as errno.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_process.py