I am the author of the post. You are right, even if you know what to code, you don't know how to code it and how part of the code is a more serious and problem

I am the author of the post. You are right, even if you know what to code, you don't know how to code it and how part of the code is a more serious and problem specific problem I think. I am not sure that we can come up with a methodology that describes how to part. I think *DD techniques help to write cleaner code. However, I don't think that implementation becomes dependent to tests / documentation when you write them first. As with your example, sorting algorithms have same goal, so their last output will be same except if you change in-place sort to not-in-place sort. Moreover, we want our interfaces stable so that no change will break any other existing code. btw, thanks for link, I didn't know that.