I have a whole section in talk-therapeutic-refactoring devoted to her characterization tests.
At one point I thought these were the same as testing-concept-discovery-tests, however they appear to be more about discovering interfaces than about discovering what the
Chuck: "something was really hard to test or really hard to put your head around. And so, by just writing some test to characterize, "I pass this in, I get this back out, I see these side effects," it at least is somewhere to start. Because then I know if I change something along the lines of those assumptions anyway, then I know about it."
At 56:24 whenever he sees a test he assumes it's there for a good reason. Characterization tests don't actually have that same meaning. They just describe the system as it is running, and don't suggest that the way it is running is actually right.
blog-post-back-discovering-tests