I am a reformed non-tester. A couple of projects ago, I started writing some tests for some particularly gnarly pieces of code that I wasn't confident were goin

I am a reformed non-tester. A couple of projects ago, I started writing some tests for some particularly gnarly pieces of code that I wasn't confident were going to stay working throughout the product's development cycle. Once I got those written, I found that I was over a hump - I was already set up with my test suite, object factories, net communications stubs, etc - all the hard work was done. At that point, I found that it became faster to write my tests and then code to make them pass than it was to develop "traditionally"; in cases where you do lot of setup or teardown for a piece of code (what happens when a user adds X to his account? Manually testing involves, adding, then testing, then clearing, then adding...), automated tested really shines. What used to take 30 seconds of manual testing time per iteration now takes a ctrl-S and 3 seconds of tests. Multiply that by 20 iterations and the time savings are significant. I'm at the point now that I write tests because it saves me time, not because it's the "right thing to do", and I'm much more confident in my code as a result. I don't test everything, but the stuff that's easily testable, high volatility, or mission critical, you betcha, that's getting tested thoroughly. The problem is that if you write, manually test, and commit a piece of code once, you're only guaranteed that it is working at the time that you commit. Two weeks down the road when you change something only mildly related, you either a) retest that "known good" code, or b) make the potentially faulty assumption that it still works. Once an app reaches a certain level of complexity, any particular change is going to require a QA department to ensure that it didn't break something else. Automated tests are your first-line QA department. Your test suite can exercise all the important bits of your code in one fell swoop, so if you break anything, it'll let you know, and quickly. The value of this cannot be understated, and once you've tasted it, you'll never want to go back.