One of my testing little dirty secrets

July 31, 2011

I recently read yet another article on TDD, and one of the things this article talked about was the benefit of reading tests in order to understand what the code was doing.

When I thought about someone doing this to my tests, I laughed hollowly.

One of the little dirty secrets about the tests I write is that they are, well, slapped together. I almost invariably write tests in the most expedient and brute force way, and I don't particularly write comments about what the tests are testing and how. (Sometimes I will write a one sentence summary of what bit of the API a test is testing, mostly because Python's unittest module encourages this.)

This goes well beyond how I'd rather have clean code and dirty tests. A good part of it is that I still have the mindset that tests are overhead, and the less time I spend on them the more time I have to spend on writing the useful things. Writing clean, carefully commented test code would require a lot more work. A part of it is that most test code is about the most boring, straightforward code that you could imagine; 'repeatedly call this routine with certain inputs and verify that you get certain outputs' is essentially boilerplate, except you can't automate it.

(I have a tendency to make my tests somewhat exhaustive. I'm not content to test that a routine works with one set of inputs, so I want to call anything important with all sorts of arguments to check basic functionality, boundary conditions, and so on.)

When I was essentially developing code for myself, this was sort of acceptable (although not great, since even I can forget what my tests were about if I was away from the code for a while). But since I've been developing code in a more shared environment I've become increasingly conscious of how hard it would be for my co-workers to understand my tests as part of developing a change to my code. Although I'm not certain what the right answer is, I suspect that it is adding more comments and more careful code structure to my tests, even though this is sure to make them slower and more annoying to write (and to revise).

(Probably I should look at how some real projects in the wild structure and document their tests, to see how people who really know TDD deal with this problem.)


Written on 31 July 2011.
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