def test_notString(self):
        """
        If something in things is not a string, it is converted into one.
        """
        sample = [1, 2, 'three']
        expected = '1, 2, and three'
        result = util._listToPhrase(sample, 'and')
        self.assertEqual(expected, result)

        If something in things is not a string, it is converted into one.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/trial/test/test_util.py