Testing vs. Checking

There is confusion in the software development business over a distinction between testing and checking. I will now attempt to make the distinction clearer.

Checking Is Confirmation

Checking is something that we do with the motivation of confirming existing beliefs. Checking is a process of confirmation, verification, and validation. When we already believe something to be true, we verify our belief by checking. We check when we’ve made a change to the code and we want to make sure that everything that worked before still works. When we have an assumption that’s important, we check to make sure the assumption holds. Excellent programmers do a lot ofchecking as they write and modify their code, creating automated routines that they run frequently to check to make sure that the code hasn’t broken. Checking is focused on making sure that the program doesn’t fail.

Testing Is Exploration and Learning

Testing is something that we do with the motivation of finding new information. Testing is a process of exploration, discovery, investigation, and learning. When we configure, operate, and observe a product with the intention of evaluating it, or with the intention of recognizing a problem that we hadn’t anticipated, we’re testing. We’re testing when we’re trying to find out about the extents and limitations of the product and its design, and when we’re largely driven by questions that haven’t been answered or even asked before.  testing is focused on “learning sufficiently everything that matters about how the program works and about how it might not work.”