The linked article is seven years old. For more up-to-date Python TDD techniques, see chapters 13 & 14 of Mark Pilgrim's 'Dive Into Python' (available free at http://diveintopython.org/), and for Python 3 (though plenty applies to Python 2) chapter 9 of 'Dive Into Python 3' (available free at http://diveintopython3.org/)