On the test automation pyramid (again), opposing views and TestBash Manchester

Short blog post this time, since I’m smack in the middle of three projects while also preparing for my talk at TestBash Manchester, some training stuff and reviewing a book. It can’t always be long form!

With this blog post, I’d like to draw your attention to episode #31 of the Test and Code podcast, where Brian Okken (the host) replayed parts of the recordings of him being on another podcast, hosted by Paul Merrill. Paul’s a great guy and someone whose opinions and view I hold in high esteem, so I knew this was about to be good. In the interviel Paul and Brian did, they shared and discussed their opposing views on the test automation pyramid. By the way, more news about a collaboration (of sorts) between Paul and myself to follow soon!

It seems like Paul roughly shares my own views on the pyramid (read this recent blog post to see what I think of it and how I still use it, whereas Brian thinks the pyramid is falsely promoting the fact that unit tests are the most important tests you can write. Instead, in the recording, he advocates that there’s no value in software until it’s useful to an end user (be it a human being or another system) and that therefore UI tests are the most important and should be treated that way. I deliberately didn’t use the word ‘graphical’ here, by the way, since Brian talks mostly about writing tests for software where the GUI isn’t the interface that’s most extensively used.

You can listen to the podcast episode here. I thought it refreshing to listen to someone that has such an alternative view on a well-worn concept such as the test automation pyramid. Even though my own opinions on the model and its use remain unchanged (for now), I’ll try and make it a habit to listen to other voices and opposing views more often, rather than staying in my comfort zone and listening to podcasts and reading blogs on topics I’m already familiar with. Who knows I might learn a thing or two!

On another note, as I said before, I’m quite busy putting the finishing touches to my upcoming TestBash Manchester talk, and it’s both a talk and an event I’m very, very excited about. To those of you with Ministry of Testing Dojo Pro accounts, my talk will be available shortly after the event. For those of you that haven’t got such an account, you’ll have to wait for next week’s blog post, which will highly likely be a review of the event.

See you next week!

Why I think unit testing is the basis of any solid automation strategy

In a recent blog post I talked about why and how I still use the test automation pyramid as a model to talk about different levels of test automation and how to combine them into an automation strategy that fits your needs. In this blog post I’d like to talk about the basis of the pyramid a little more: unit tests and unit testing. There’s a reason -or better, there are a number of reasons- why unit testing forms the basis of any solid automation strategy, and why it’s depicted as the broadest layer in the pyramid.

Unit tests are fast
Even though end-to-end testing using tools like Selenium is the first thing a lot of people think about when they hear the term ‘test automation’, Selenium tests are actually the hardest and most time-intensive to write, run and maintain. Unit tests, on the other hand, can be written fast, both in absolute time it takes to write unit test code as well as relative to the progress of the software development process. A very good example of the latter is the practice of Test Driven Development (TDD), where tests are written before the actual production code is created.

Unit tests are also fast to run. Their run time is typically in the milliseconds range, where integration and end-to-end tests take seconds or even minutes, depending on your test and their scope. This means that a solid set of unit tests will give you feedback on specific aspects of your application quality much faster than those other types of tests. I stressed ‘specific aspects’, because while unit tests can cover ground in relatively little time, there’s only so much they can do. As goes for automation as a whole.

Unit tests require (and enforce) code testability
Any developer can tell you that the better structured code is, the easier it is to isolate specific classes and methods and write unit tests for them, mocking away all dependencies that method or class requires. This is referred to as highly testable code. I’ve worked in projects where people were stuck with badly testable code and have seen the consequences. I’ve facilitated two day test automation hackathon where the end goal was to write a single unit test and integrate it into the Continuous Integration pipeline. Writing the test took ten minutes. Untangling the existing code so that the unit test could be written? Two days MINUS ten minutes.

This is where practices like TDD can help. When you’ve got your tests in place before the production code that lets the tests pass is written, the risk of that production code becoming untestable spaghetti code is far lower. And having testable code is a massive help with the next reason why unit testing should be the basis of your automation efforts.

Unit tests prevent outside in test automation (hopefully)
If you’re code is testable, it means that it’s far easier to write unit tests for it. Which in turn means that the likelihood that unit tests are actually written increases as well. And where unit tests are written consistently and visibly, the risk that everything and its mother it tested through the user interface (a phenomenon I’ve seen referred to as ‘outside-in test automation’) is far less high. Just writing lots of unit tests is not enough, though, their scope, intent and coverage should be clear to the team as well (so, testers, get involved!).

Unit tests are a safety net for code refactoring
Let’s face it: your production code isn’t going to live unchanged forever (although I’ve heard about lines of COBOL that are busy defying this). Changes to the application, renewed libraries or insights, all of these will in time be reason to refactor your existing code to improve effectivity, readability, maintainability or just to keep things running. This is where a decent set of unit tests helps a lot, since they can be used as a safety net that can give you feedback about the consequences of your refactoring efforts on overall application functionality. And even more importantly, they do this quickly. Developers are humans, and will move on to different tasks if they need to wait hours for feedback. With unit tests, that feedback arrives in seconds, keeping them and you both focused and on the right track.

In the end, unit tests can, will and need not replace integration and end-to-end tests, of course. There’s a reason all of them are featured in the test automation pyramid. But when you’re trying to create or improve your test automation strategy, I’d advise you to start with the basis and get your unit testing in place.

By the way, for those of you reading this on the publication date, I’d like to mention that I’ll be co-hosting a webinar with the folks at Testim, where I’ll be talking about the importance of unit testing, as well as much more with regards to test automation strategy. I hope to see you there! If you’re reading this at a later date, I’ll add a link to the recording as soon as it’s available.

Why and how I still use the test automation pyramid

Last week, while delivering part one of a two-evening API testing course, I found myself explaining the benefits of writing automated tests at the API level using the test automation pyramid. That in itself probably isn’t too noteworthy, but what immediately struck me as odd is that I found myself apologizing to the participants that I used a model that has received so many criticism as the pyramid.

Odd, because

  1. Half of the participants hadn’t even heard of the test automation pyramid before
  2. The pyramid, as a model, to me is still a very useful way for me to explain a number of concepts and good practices related to test automation.

#1 is a problem that should be tackled by better education around software testing and test automation, I think, but that’s not what I wanted to talk about in this blog post. No, what I would like to show is that, at least to me, the test automation pyramid is still a valuable model when explaining and teaching test automation, as long as it’s used in the right context.

The version of the test automation pyramid I tend to use in my talks

The basis of what makes the pyramid a useful concept to me is the following distinction:

It is a model, not a guideline.

A guideline is something that’s (claiming to be) correct, under certain circumstances. A model, as the statistician George Box said, is always wrong, but some models are useful. To me, this applies perfectly to the test automation pyramid:

There’s more to automation than meets the UI
The test automation pyramid, as a model, helps me explain to less experienced engineers that there’s more to test automation than end-to-end tests (those often driven through the user interface). I explain this often using examples from real life projects, where we chose to do a couple of end-to-end tests to verify that customers could complete a specific sequence of actions, combined with a more extensive set of API tests to verify business logic at a lower level, and why this was a much more effective approach than testing everything through the UI.

Unit testing is the foundation
The pyramid, as a model, perfectly supports my belief that a solid unit testing strategy is the basis for any successful, significantly-sized test automation effort. Anything that can be covered in unit tests should not have to be covered again in higher level tests, i.e., at the integration/API or even at the end-to-end level.

E2E and UI tests are two different concepts
The pyramid, as a model, helps me explain the difference between end-to-end tests, where the application as a whole is exercised from top (often the UI) to bottom (often a database), and user interface tests. The latter may be end-to-end tests, but unbeknownst to surprisingly many people you can write unit tests for your user interface just as well.There’s a reason the top layer of the pyramid that I use (together with many others) says ‘E2E’, not ‘UI’…

Don’t try to enforce ratios between test automation scope levels
The pyramid, when used as a guideline, can lead to less than optimal test automation decisions. This mainly applies to the ratio between the number of tests in each of the E2E, integration and unit categories. Even though well though through automation suites will naturally steer towards a ratio of more unit tests than integration tests and more integration tests than E2E tests, it should never be forced to do so. I’ve even seen some people, which unfortunately were the ones in charge, make decisions on what and how to automate based on ratios. Some even went as far as saying ‘X % of our automated tests HAVE TO be unit tests’. Personally, I’d rather go for the ratio that delivers in terms of effectiveness and time needed to write and maintain the tests instead.

Test automation is only part of the testing story
‘My’ version of the test automation pyramid (or at least the version I use in my presentations) prominently features what I call exploratory testing. This helps remind me to tell those that are listening that there’s more to testing than automation. I usually call this part of the testing story ‘exploratory testing’, because this is the part where humans explore and evaluate the application under test to inform themselves and others about aspects of its quality. This is what’s often referred to as ‘manual testing’, but I don’t like that term.

As you can see, to me, the test automation pyramid is still a very valuable model (and still a useless guideline) when it comes to me explaining my thoughts on automation, despite all the criticism it has received over the years. I hope I never find myself apologizing for using it again in the future..