One advantage of test-driven development I’ve rarely seen emphasized is that it enables experimental programming. This was recently brought home to me while I was working on XOM. Steve Loughran had requested the ability to use a
NodeFactory when converting from a DOM document. It was a reasonable request so I set off to implement it.
My first iteration satisfied Steve’s use-case. It was actually a fairly major rework of the code, but the test suite assured me that it all worked and I hadn’t broken anything that used to work. However, Wolfgang Hoschek quickly found a real bug in the new functionality I had added; and things got a little sticky here.
To satisfy John Cowan, the
DOMConverter uses some fancy non-recursive algorithms. This enables it to process arbitrarily deep documents without stack overflows. However the algorithm is far from obvious; and even though the code is well-written it’s hard to come back to it a couple of years later and figure out just how it works.
But this is where test-driven development really shines: I don’t have to understand the code to fix it. (more…)