Test driven development

[Neil Cerutti]

On 1/24/08, ajcppmod at gmail.com <ajcppmod at gmail.com> wrote:
> Hi
>
> Sorry if this is a bit off topic but as unit testing is such a
> cornerstone of python development I thought a few of you may be able
> to share your knowledge/experiences.

Test driven development, simplistically, means to write the tests
before you write the code.

> I like the concept of TDD but find it difficult to put into practice
> most of the time. I think this primarily because I tend to like top-
> down development and functional/object decomposition and TDD feels
> more like a bottom-up approach.

It should work with any unit of development, although it can be hard
to usefully test high-level functionality that depends on currently
unimplemented underware.

> So my question is when approaching a project that you want to employ
> test driven development on how and where do you start? And also if
> anyone uses top-down design with TDD I would be interested in how you
> do it (does it involve lots of mock objects/ is the first test you
> write the last one to pass)?

The system I've adopted is to use inline doctests for the simplest,
tutorial-like examples, with "outline" unit tests composd to verify
implementation details and to probe bounderies. Typically, I write a
doctest, then the routine, and finally the unit tests.

Top-down should work fine with test-driven, although your highest
level tests will fail until your low-level tests pass. All the failing
tests might be kind of depressing, though. Personally, I haven't
really given top-down a fair shake, so I don't know which approach
reveals my stupid design mistakes faster.

-- 
Neil Cerutti <mr.cerutti+python at gmail.com>