Unit tests rock, I suck, news at 11

I’ve just started looking at my Miscellaneous Utility Library again, after quite a while. I’m currently running Vista on my laptop, which means I can’t run Visual Studio 2003 – so it’s about time I updated the library to use generics and all that goodness. I’ll keep the .NET 1.1 version available on the web site, but from now on any new code will be 2.0 only.

In the process of updating RandomAccessQueue to use implement the generic collection interfaces, I decided to do the implementation test-first, as is now my habit. It clearly wasn’t habit back when I originally wrote the code (the same day Peramon laid everyone off, incidentally – I remember as I was at home, ill). The new methods use some of the old methods – and unfortunately that’s now exposed some long-standing bugs.

Looking back, I find it hard to understand why I had so much faith in this code: it’s the kind of code which is bound to suffer from off-by-one errors and the like. It’s not terribly hard to test, fortunately (unlike the threadpool stuff, for example). Oh how I wish I’d been using NUnit back then.

This happened the last time I looked at a MiscUtil class, too. It will take a while to add unit tests giving a decent level of coverage to the code – it’s not like I have a lot of spare time – but it’s clearly got to be done.

I wonder how much other code I’ve written over the years is riddled with bugs? To be fair, the MiscUtil stuff was run considerably less than most of the code I wrote professionally at Peramon… but I bet there were quite a few nasty little gotchas waiting there too. And now?
No, I don’t write perfect code, even with unit tests. Even when the code does what I intend it to do, I have to revisit whether the intention was right in the first place. Even with unit tests there can easily be problems which slip through the cracks – but I don’t think I produce nearly as much code which is basically broken as I used to.