Why the Testing Pyramid is Misleading
As testers, we often hear about the Software Testing Pyramid. I myself have talked about it many times in my blog and on my podcast.
What is the Testing Pyramid?
For those of you that aren’t familiar with the testing pyramid, it’s basically a way to break down the type of test case distribution you should have for testing your development efforts. This breakdown resembles a pyramid, and is one of the more popular concepts QA teams use when planning their testing efforts.
Unit Tests makes up the largest section of the pyramid, forming a solid base. Unit tests are the easiest to create and yield the biggest “bang for the buck.” Since unit tests are usually written in the same language an application is written in, developers should have an easy time adding them to their development process.
The middle of the pyramid consists of Integration Tests. They’re a little more expensive, but they test a different part of your system.
GUI testing is at the top of the pyramid, and represents a small piece of the total number of automation test types that should be created.
The Testing Pyramid is Flawed
Sounds reasonable, but I think a concept can sometimes be misused and misunderstood. And honestly, sometimes the testing pyramid itself is misleading. I spoke with Todd Gardner of TrackJs recently, and he believes that the testing pyramid concept is flawed for two main reasons.
The first reason is that it misses market risk. Determining whether or not the project itself is a good idea, and how do you test that? In other words, operating at a level above system tests.
Todd’s second problem with the model is that it implies volume. It’s basically saying you should have more unit tests than integration tests because unit tests are cheap to write — and he believes that’s missing the point. It shouldn’t be about how what it costs to write and maintain, but rather what kind of risks are being addressed by these sorts of tests.
The question of “Are you testing the right thing?” I don’t think is asked often enough, because it’s really hard~@toddhgardnerClick to tweet
Does it always make sense to adhere to the Testing Pyramid?
Todd goes on to say that a lot of web applications he tends to write today are really trivial. He’s simply trying to demonstrate a concept, or attempting to build a CRUD App for some purpose, and he’s basically converting SQL into HTML and back. In those sort of apps, there’s very little functional complexity happening. Normally, you have a framework that you’ve shoved in place that’s handling and abstracting all that stuff away.
He doesn’t really see much risk in the functional logic at that level, so he tends not to write many unit tests in that situation. If it works, it works, and if it doesn’t work, it’s not going to work. There’s not a whole lot complexity at that level.
There is complexity, however at an integration level: “Can my app talk to my database?” and, “Am I writing queries correctly?” Todd will write some integration tests around that. “Am I presenting a user interface that makes sense?” He’ll write some system tests around that.
Depending on the app, he might have completely inverted the Pyramid. He may have ten system tests, five integration tests, and one unit test for the one actual, interesting piece of logic he had in an app, which totally messes with that metaphor of a “pyramid.”
Scales, not Pyramids
Todd firmly believes we should think scales instead of pyramids when it comes to software development testing. Rather than prescribing how many of one kind of test you should have over another, you should look at, say, “What kind of risks exist in my system? How can my system break?” and build up the testing coverage that you need in each of those areas to address the risks of the system. Software development and testing are really all about risk.
What is Software Risk?
As Matt Heusser from Test Talks Episode 61 explains it,
“We can look at the risk of building the wrong thing that is not going to be fit for use. That’s product risk.
We can look at the risks that are injected from theory that we learned from a book, and then try to implement that process on our teams only to find that it doesn’t really work for us, and that’s process risk. Of course, there’s a software buggy risk.”
The Heuristic Test Strategy Model has a half-dozen different ways to look at all the risks on a project~@mheusserClick to tweet
It all about Risk
So how does risk fit into our testing efforts? Matt recommends using the Heuristic Test Strategy Model, which has a half-dozen different ways to look at all the risks in a project.
If you go through all the risks on the project in a systematic way, you identify which risks you want to do something about. You figure out the kinds of different ways you can address those risks, and you stand that up against the consequences. If those things break, you sort that, and you go through it until you run through the amount of time you’re willing to invest.
That’s a whole lot more responsible. It’s better testing than the kind of requirement-based testing that many testers end up following.
- How to Reduce the Cost of Software Testing – Matt Heusser
- Case Studies in Terrible Testing Todd Garder 2015 OreDev video presentation