[lyudmil]

I think there are three more reasons to do unit tests I wish the author had mentioned:

1. Not only do they prevent you from messing your code up because you forgot how it actually worked, they prevent you from having to think about how and whether you've messed something up. I find this to be a creativity boost.

2. By helping you maintain the same level of quality, they ensure that if you don't add any new features but keep fixing bugs (and unit testing the fixes), your bug-count will go down. That's a good property for a system to have.

3. They give you the freedom to quickly and securely change your design, which in turn means you can keep improving quality, which in turn means you maintain higher productivity in the long run.

With this in mind the it seems the author's suggested alternative approaches fall short of what unit tests can do.