def test_copyToFileClosing(self):
        """
        If an exception is raised while L{FilePath.copyTo} is copying bytes
        between two regular files, the source and destination files are closed
        and the exception propagates to the caller of L{FilePath.copyTo}.
        """
        destination = ExplodingFilePath(self.mktemp())
        source = ExplodingFilePath(__file__)
        self.assertRaises(IOError, source.copyTo, destination)
        self.assertTrue(source.fp.closed)
        self.assertTrue(destination.fp.closed)

        If an exception is raised while L{FilePath.copyTo} is copying bytes
        between two regular files, the source and destination files are closed
        and the exception propagates to the caller of L{FilePath.copyTo}.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_paths.py