Check out A Dozen Reasons Why Test-First Is Better Than Test-Later (Pt. 1) by Rob Myers. Here is an excerpt:
An editor of Dr. Dobbs magazine once wrote to me—replying to my response to an article—“All the benefits [of Test-Driven Development] could be attained equally by writing tests after the code, rather than before.”[1]
Tests exercise software to be sure it’s doing what was intended. So,…
The full article is available here.