def METHOD_NAME(self):
    '''
    Take time object and create ISO string from it.
    This is the reverse test to test_parse.
    '''
    if expectation is None:
        self.assertRaises(AttributeError,
                          time_isoformat, expectation, format)
    elif format is not None:
        self.assertEqual(time_isoformat(expectation, format),
                         timestring)