def test_it(self):
        # Internally shutil.copyfile() can use "fast copy" methods like
        # os.sendfile().
        size = os.path.getsize(TESTFN)
        shutil.copyfile(TESTFN, TESTFN2)
        self.assertEqual(os.path.getsize(TESTFN2), size)
        with open(TESTFN2, 'rb') as f:
            self.assertEqual(f.read(5), b'z\x00\x00\x00\x00')
            f.seek(size - 5)
            self.assertEqual(f.read(), b'\x00\x00\x00\x00a')