I thought I was being pretty clever.
I was being very stupid. I'd just re-invented xUnit, and didn't even know. 
It's a particular type of stupidity that manifests itself only in those who'd otherwise regard themselves as anything but: we get so wrapped up in our great idea that we stop to consider that someone else might have done this already. Programmers are particularly badly afflicted by this, mostly because it suits our vanity to create it ourselves.
There was already an automated testing community, that had over time evolved what worked and what didn't, the practical upshot of which - for a .Net developer at the time - was that NUnit already existed. I could have spent the time writing more tests instead. Or better still, more screens, which is what I was actually being paid for.
The last three applications I've worked on have all involved considerable custom frameworks (stupid) including a custom databinding scheme (very stupid). They were written by clever people, most of whom I respect, but they did some stupid things that less able programmers wouldn't have been able to do. Clever isn't always a complement in the agile camp, and this is why.
Of course 5 years of hindsight is a wonderful thing, and I've written my share of head-slappingly dumb code too. And it's all too easy to succumbed to the 'quick fix' fallacy when the boss is breathing down your neck : after all it's so much easier to get started writing your own framework than to learn to use someone else's.
But once you start down the dark path, forever will it haunt your destiny. Which is why I make this plee to you now:
Please, before you put finger to keyboard again, consider whether what you're about to write has already been written.Don't be stupid.
 To be fair to my erstwhile self, at least I was actually doing some testing, which was more than had been done before on that project
 Or that particular project at any rate