I recently read Mike Jansen's 8th Light blog post on The Gilded Rose kata in Clojure and thought I'd give it a crack myself.
First was to get a set of tests setup. The kata is already setup to use the speclj testing library. I'd only used the very fine Midje library for testing in Clojure before, but I thought I'd stick with what was already in the project.
Both allow for very easy and straightforward testing, and both support automatic test running when files change. This makes for a really tight feedback loop when making any changes.
I tried as much as possible to just translate the requirements into a suite of tests without getting bogged down in implementation details. Here it is after the refactoring.
Not very much changed between initially writing the tests and refactoring the main code, just a few bits here and there to match changes made in the core file.
Refactoring the main code basically comprised of splitting each of the different behaviours spread around update-quality into their own functions which could be associated with different items in a declarative fashion. The update-quality function then just became a matter of mapping these functions over the items.
The restriction on being unable to change the item function made this approach a little more convoluted, but best not to enrage the goblin.
Here's the refactored core file.
There's bits I'd like to tweak, but I also wanted to time box it within a reasonable range. One thing I would like to do would be to try core.match on some of the functions; particularly the one relating to concert ticket quality.