There are many technical reasons to chose (or not chose!) to use Test Driven Development. In my opinion, one of the most important benefits isn’t technical at all – it’s that it forces you to have an opinion! When you decide what you are going to test, you are forming an opinion on what you want your code to do. It might be processing an input, transforming an input, or providing output based on current state. You have an opinion on the end state but leave the implementation to be determined.
I liken this to having an outline for writing. If you start writing without an outline, the end result never seems to match what you thought you’d end up with. If you follow an outline, however sparse, the result matches what you thought you’d up with – if not, you didn’t follow the outline. Sure, it requires some revisions here and there to make it all tidy, but at least your first draft is legible.
When considering whether you should employ Test Driven Development, keep this in mind as a non-technical benefit!