If you didn’t test it, it doesn’t work

Gary Bernhardt has a great talk online from 2012 called Boundaries, about how design patterns influence, for better and worse, the testing that can be done. In particular he advocates a “core” and “shell” model, having many independent functional cores and one orchestrating shell around them. The idea is that each functional core can be tested independently from the others more effectively by not having to worry about mocks and dependencies. The tests of each core can be greatly simplified, while focusing on what it’s actually supposed to do.

The concept is definitely solid, but I do take issue with one thing he says towards the end. I’ll acknowledge upfront that I’m drawing much more meaning from his choice of words than I think was intended, it just happened to strike a nerve. It happens at about the 29m30s mark, when he’s describing how small the tests for the functional cores became in his example program. As for the shell, the orchestrating code responsible for connecting the wires between these cores, he says:

The shell is actually untested. The only conditional in the shell is the case statement that we saw that was choosing between keys. There’s no other decision made in the entire shell. So I don’t even really feel the need to test it. I fire the program up, I hit ‘j’, as long as that worked, pretty much the whole thing works.

The obvious objection here is that just because the cores work independently doesn’t mean that the shell manipulates those cores correctly. Conditionals aren’t the only things that can have bugs in them. But that’s not my objection. It’s this:

Firing the program up and hitting ‘j’ to see if that works is testing it.

Are there other tests he could do? Sure. At a minimum, ‘j’ isn’t the only keystroke the program supports. So he’s made a risk assessment that the shell is simple enough that this is the only test he needs. It might be an informal assessment, even an unconscious one, but it’s still based on the foundation of unit tests, his knowledge of how the program works, and how it’s going to be used. There’s absolutely nothing wrong with that.

Has he automated his test? No. But is something only a test if it’s automated? Also no. Much like he made a risk assessment that he only needs one test, there’s also a judgement call (perhaps implicit) that this one test isn’t worth automating. There could be any number of reasons for making that call. That doesn’t mean the sequence of firing it up and trying it out is something outside of “testing it”.

I think there is a tendency these days to think that a test only counts if it’s automated, but we should know better than that. It’s been argued that the parts we automate shouldn’t even be called “tests”. Whether or not you agree with the terminology, it has to be acknowledged that testing encompasses a lot more than automating some checks.

I think this same sentiment is what motivates the #NoTesting hashtag on Twitter. If you have a traditional, waterfall style, gated, or heavily regimented picture of what software testing is, you’ll exclude from that umbrella all kinds of other activities that people naturally do to poke at their products. “We don’t want that stuffy bottleneck-creating deadline-breaking time-suck kind of testing around here”, they say, “so therefore we don’t want testing at all.” I bring this up not to put Gary into that camp—in the context of the talk this quibble of mine wouldn’t affect the point he was making—but to point out that people do take this idea too far.

Coincidentally, the same day I came across this talk, I also read The Honest Manual Writer Heuristic by Michael Bolton. It ends with a line that captures this idea that people do a lot more testing than they realize:

Did you notice that I’ve just described testing without using the word “testing”?

If you didn’t test it, it doesn’t work.

or, to make it perfectly clear what I’m getting at, let’s phrase it like this:

If you know it works, you must have tested it.