The T in FIRST didn't mean Thorough originally. The T was for Timely. There's a post by Tim Ottinger on his blog "Tim Ottinger's thoughts on Software Development" that explains the history of the FIRST acronym: FIRST: an idea that ran away from home Google it because it seems that as a new users I can't add inks in comments. I agree with you. I think that I, R and S can be applied to other type of tests other than unit-tests. I liked your post. Thank you!