def test_isRunningInit(self):
        """
        L{PIDFile.isRunning} returns true for a process that we are not allowed
        to kill (errno=EPERM).

        @note: This differs from L{PIDFileTests.test_isRunningNotAllowed} in
        that it actually invokes the C{kill} system call, which is useful for
        testing of our chosen method for probing the existence of a process
        that we are not allowed to kill.

        @note: In this case, we try killing C{init}, which is process #1 on
        POSIX systems, so this test is not portable.  C{init} should always be
        running and should not be killable by non-root users.
        """
        if SYSTEM_NAME != "posix":
            raise SkipTest("This test assumes POSIX")

        pidFile = PIDFile(DummyFilePath())
        pidFile._write(1)  # PID 1 is init on POSIX systems

        self.assertTrue(pidFile.isRunning())

        L{PIDFile.isRunning} returns true for a process that we are not allowed
        to kill (errno=EPERM).

        @note: This differs from L{PIDFileTests.test_isRunningNotAllowed} in
        that it actually invokes the C{kill} system call, which is useful for
        testing of our chosen method for probing the existence of a process
        that we are not allowed to kill.

        @note: In this case, we try killing C{init}, which is process #1 on
        POSIX systems, so this test is not portable.  C{init} should always be
        running and should not be killable by non-root users.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/application/runner/test/test_pidfile.py