In this post: rules 7, 8, and 9; which discuss testing and debugging. They are all related in a way: having to do with making good-quality craft work. Because, as much as computer people like to believe that we're "engineers" or that this is "computer science", we're not really. We're crafts people, in a profession that's still very young and finding its roots and methods in order to be consistently successful.
I'm definitely not trying to pretend I'm an "engineer". For real rigour, there is much more required than a few simple rules. But these are some realistic and humble rules in the area of testing that I aim to stick to.