def test_casePreservation(self):
        """
        L{dns._nameToLabels} preserves the case of ascii
        characters in labels.
        """
        self.assertEqual(
            dns._nameToLabels(b'EXAMPLE.COM'),
            [b'EXAMPLE', b'COM', b''])

        L{dns._nameToLabels} preserves the case of ascii
        characters in labels.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/names/test/test_dns.py