def test_devFDImplementation(self):
        """
        L{_FDDetector._devFDImplementation} raises L{OSError} if there is no
        I{/dev/fd} directory, otherwise it returns the basenames of its children
        interpreted as integers.
        """
        self.devfs = False
        self.assertRaises(OSError, self.detector._devFDImplementation)
        self.devfs = True
        self.accurateDevFDResults = False
        self.assertEqual([0, 1, 2], self.detector._devFDImplementation())

        L{_FDDetector._devFDImplementation} raises L{OSError} if there is no
        I{/dev/fd} directory, otherwise it returns the basenames of its children
        interpreted as integers.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/internet/test/test_posixprocess.py