In Test We Trust

Have you ever thought about how much trust testing gets in your projects?

Isn’t it strange that in IT projects you have a group of people that you don’t seem to trust? Developers! I mean, why else would you have one or more dedicated test stages to control and double-check the work of the developers? Developers often don’t even trust their own work, so they add tests to it to validate that the code they write is actually doing what it should.

And of course you trust your developers to do a good job, but you don’t trust your system to remain stable. That’s even better! So you create a product that you don’t trust, except when you have tested it thoroughly. And only then you probably have enough trust to send it to a customer.

Testing is all about trust. We don’t trust our production process without evaluating it every now and then. Let’s take some manufacturing industries, they have many decades, even centuries more of experience than IT. They create processes and tools and machines to produce many pieces of the same kind. Expecting it to have the specified properties and reaching the expected quality aspects every time. Depending on the product, they check every piece (like automobiles) or just rare and random spot checks (for example screws and bolts). They trust their machines – usually to a high degree – to reproduce a product thousands or even millions of times.

We are in IT, we don’t reproduce the same thing over and over again.
Can you imagine that for your project you only do some random spot checks, and only check for a handful of criteria each time? If your answer is ‘yes’, then I wonder if you usually test more and why you still test it. If your answer is ‘no’, you belong to what seems to be the standard in IT.

So, what we have established now is, that we don’t overly trust the outcome of our development process. Except when we have some kind of testing in place.

Have you ever realized how much decision makers rely on their trust in test results? If you are a developer, BA, PO, or a tester, who is part of the testing that happens in your delivery process, have you ever felt the trust that is put into your testing? Decision makers rely on your evaluation or the evaluation of the test automation you implemented!

Does your project have automated tests? Do you trust the results of your tests? Always? Do you run them after every check-in, every night, at least before every delivery? Do you double-check the results of your automated tests? When you implement new features, when you refactor existing code, when you change existing functionality, you re-run those tests and let them evaluate if something changed from their expectations. You trust your automated tests to warn you in case something has been messed up. The last code change, a dependency upgrade, a config change, refactoring an old method.

Do you put enough care into your automated tests, that you can really rely on them to do what you want them to do? Why do you have that trust in your tests, but probably not in your production code? And I don’t ask the question “who tests the tests?”

Of course we do some exploratory testing in addition to our test automation. And sure, sometimes this discovers gaps in your test coverage, but most of all exploratory testing is to cover and uncover additional risks, that automation can not supply. So, when you established exploratory testing in some form, alongside your change detection (a.k.a. test automation), you add another layer of trust, or respectively distrust to some parts of your system.

This is not about distrust, we just want to be sure that it works!

In one of my last consulting gigs for QualityMinds, I had an assignment for a small product company, to analyze their unit tests and make suggestions for improvement. The unit test set was barely existent, and many of the tests I checked were rarely doing anything useful. That wasn’t a big problem for the delivery process, as they have a big QA team who is doing lots of (end-to-end) testing before deployment, and even the developers help in the last week before delivery.

Yet they have a big problem. They don’t have enough trust in their tests and test coverage to refactor and modernize their existing code base. So my main message for the developers was to start writing unit tests that they trust. If you have to extend a method, change functionality, refactor it, debug it, fix something in it, you want to have a small test set in place that you can trust! I don’t care about code coverage, path coverage, or whatever metric. The most important metric is, that the developers trust the test set enough to make changes and receive fast feedback for their changes and that they trust that feedback.

I could add more text here about false negatives, false positives, flaky tests, UI tests, and so many more topics that are risks to the trust that we put into our change detectors.
There are also risks in this thing that is often referred to as “manual testing”. When it is based on age-old pre-defined test cases, or outdated acceptance criteria. Even when you do exploratory testing and use your brains, what are the oracles that you trust? You don’t want to discuss every tiny bit of the software with your colleagues all the time, if it makes sense or not.

We can only trust our tests, if we design them with the necessary reliability. The next time you design and implement an automated test, think about the trust you put into it. The trust that you hand over to this piece of code. Is it reliable to detect all the changes you want it to detect? When it detects a change, is it helpful? When you don’t change the underlying code and run the test 1000 times, does it always return the same result? Did you see your test fail, when the underlying code changes?

PS: This blog post was inspired by a rejected conference talk proposal that I submitted for TestBash Philly 2017. All that time since then, I wanted to write it up. Now was the time!

2 thoughts on “In Test We Trust”

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