Uncle Bob recently made an interesting post on TDD and test generators, and I couldn’t agree more! I’ve always despised test generators myself, mostly for the same reasons Martin makes.

In my opinion, desiring to use a test generator on fresh code is an attempt to cut corners and bypass testing, which really is counterproductive. From my experience thus far, writing code test first has helped me write more loosely couple code, while both legacy code and code written test last usually end up being a tightly coupled mess. Even if you design nice, loosely coupled code and generate the tests for it, there is still the problem that the test generator is not really going to be smart enough to figure out your domain logic, and TDD is a helpful tool for expressing domain logic in the form of both test inputs/outputs and object behavior.

Like Bob mentions, it’s helpful to use generators to provide coverage for a legacy code base (especially when refactoring… I once spent a couple days writing tests around a legacy system to prepare it for refactoring!) but if you’re using them for a fresh code base, you’re of course not doing TDD… and you lose all the benefits you could reap from practicing TDD!

As an aside, I noticed he mentioned that 33% of the codebase for fitnesse was unit tests… I’d go further and argue that one should aim for 50-60% of their codebase being composed of unit tests! I’m just extreme like that. ;)

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This entry was posted on Thursday, January 10th, 2008 at 11:07 pm and is filed under Agile Software Development, Test Driven Development, Thoughts. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.