I used to hate tests, but now I love them.
When possible, I prefer to write the tests first - and yes, it can help you catch a kludgy implementation earlier.
Sometimes, when refactoring older code, I find it easier to do the rewrite first, because I often don't fully understand what I'm refactoring when I start, so my tests would be way off.
Andy Lester has written some great stuff on the joys of testing. I recommend this (HTML version). If that doesn't convince you of the benefits of a good testing strategy, I don't think anything will :)
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