What should a “unit” be when unit testing?

Question

On Proggit today I was reading the comment thread on a submission entitled, \"Why Unit Testing Is A Waste of Time\".

I\'m not really concerned with premise of the ar

Answer 1

I've always tested at the function level, and that's worked just fine. The big point for me is that unit testing tests the contract between two pieces of code. The unit test just acts as a caller, and ensures that the code being tested (no matter how large - a single function or a huge, nested library that takes 30 minutes to test) returns results in a predictable way.

The whole point of a unit test it to ensure compatibility (by not breaking intereactions) and ensure predictable results. Testing at any place there's an exchange of information will help stabilize your application.

UPDATE: I've also always added a unit test whenever a customer or user reports an edge case that breaks an interaction in my application. Fixing it isn't sufficient for me - adding a unit test to ensure that the fix holds prevents regression, and helps keep things stable down the line.