[kstenerud]

I've used it for almost 2 decades now. The general rule is:

Don't write tests until you're sure about your design and interface. If you're doing exploratory coding, you write tests later. If you're adding features to something that already exists, you're more likely to write tests first.

The end target is roughly the same: 80-90% test coverage. But you'll waste a lot less time throwing test code away.