This is what I was alluding to when I mentioned that it's not obvious when tests should be written. It simply isn't practical to write them as part of a quick p

This is what I was alluding to when I mentioned that it's not obvious when tests should be written. It simply isn't practical to write them as part of a quick prototype (or any other rapid iteration). But writing them at the end of a project may also be difficult due to the need to move on to something else. The same argument holds for things like documentation...