Unit testing, and why it’s a Good Thing (IMO, YMMV)

OK, so there’s a codeplex project set up with no content as yet, and a 30-day deadline to get something in and published. Nothing like a bit of pressure to turn a chap’s thoughts to prevaricating. Why a “unit testing framework” for Excel VBA? Let me see if I can put together a potted history. Some years ago I became infected with the Agile development virus. Some of the practises they described reflected things I’d figured out for myself over the years, some made immediate sense in a “why didn’t I think of that?” way and some I’m still struggling to really get to grips with. Concepts like refactoring , for example, just gave names and descriptions to things I’d been doing for years. I had not, however, put the idea of constant refinement together with automated testing, the idea of which was a revelation. Further, the Refactoring book led me into methodological areas such as Extreme Programming (XP), on...