The case against detailed tests cases (part one)

We recently read an article on the QA Revolution website, titled 7 Great Reasons to Write Detailed Test Cases, which claims to give “valid justification to write detailed test cases” and goes as far as to “encourage you to write more detailed test cases in the future.” We strongly disagree with both the premise and the “great reasons” and we’ll argue our counter position in a series of blog posts.

What is meant by detailed test cases?

This was not defined in the article (well there’s a link to “test cases” – see article extract below – but it leads to a page with no relevant content – was there a detailed test case for this?). As we have no working definition from the author, this article is assuming that detailed test cases are those that comprise predefined sections, typically describing input actions, data inputs and expected result. The input actions are typically broken into low level detail and could be thought of as forming a string of instructions such as “do this, now do this, now do this, now input this, now click this and check that the output is equal to the expected output that is documented”.

Let’s start at the very beginning

For the purposes of this article, the beginning is planning. The article makes the following supporting argument for detailed test cases

It is important to write detailed test cases because it helps you to think through what needs to be tested. Writing detailed test cases takes planning. That planning will result in accelerating the testing timeline and identifying more defects. You need to be able to organize your testing in a way that is most optimal. Documenting all the different flows and combinations will help you identify potential areas that might otherwise be missed.

Let’s explore the assertions made by these statements.

We should start by pointing out that we agree that planning is important. But test planning can be accomplished in many different ways and the results of it documented in many different ways – as always, context matters!

Helps you to think through what needs to be tested

When thinking through what needs to be tested, you need to focus on a multitude of factors. Developing an understanding of what has changed and what this means for testing will lead to many different test ideas. We want to capture these for later reference but not in a detailed way. We see much greater value in keeping this as “light as possible”. We don’t want our creativity and critical thinking to be overwhelmed by details. We also don’t want to fall into a sunk cost fallacy trap by spending so much time documenting an idea that we then feel we can’t discard it later.

Planning can be made an even more valuable activity when it is used to also think of “what ifs” and looking for problems in understanding as the idea and code is developed, while “detailed test cases” (in the context of this article) already suggests waterfall and the idea that testers do not contribute to building the right thing, right.

Another major problem with planning via the creation of detailed test cases is the implication that we already know what to test (a very common fallacy in our industry). In reality, we know what to confirm based on specifications. We are accepting, as correct, documentation that is often incorrect and will not reflect the end product. Approaching testing as a proving, rather than disproving, or confirming over questioning activity plays to confirmation bias. Attempting to demonstrate that the specification is right and not considering ways it could be wrong does not lead us into deeper understanding and learning. This is a waste of tester time and skills.

That planning will result in accelerating the testing timeline and identifying more defects

We are a bit surprised to find a statement like this when there is no evidence provided to support the assertion. As testing has its foundations in evidence, it strikes us as a little strange to make this statement and expect it to be taken as fact. We wonder how the author has come up with both conclusions.

Does the author simply mean that by following scripted instructions testing is executed at greater speed? Is this an argument for efficiency over efficacy? We’d argue, based on our experiences, that detailed test cases are neither efficient nor effective. True story – many years ago Paul, working in a waterfall environment, decided to write detailed test cases that could be executed by anybody. At that point in test history this was “gold standard” thinking. Three weeks later, Paul was assigned to the testing. Having been assigned to other projects in the meantime he came back to this assignment and found the extra detail completely useless. It had been written “for the moment”. With the “in the moment knowledge” missing, the cases were not clear and it required a lot of work to get back into testing the changes. If you’ve ever tried to work with somebody else’s detailed test cases, you know the problem we’re describing.

Also, writing detailed test cases, as a precursor to testing, naturally extends the testing timeline. The ability to test early and create rapid feedback loops is removed by spending time writing documentation rather than testing code.

Similarly “identifying more defects” is a rather pointless observation sans supporting evidence. This smacks of bug counting as a measure of success over more valuable themes such as digging deeply into the system, exploring and reporting that provides evidence-based observations around risk. In saying “identifying more defects”, it would have been helpful to indicate alternative approaches being compared against here.

Defects are an outcome of engaging in testing that is thoughtful and based on observation of system responses to inputs. Hanging on to scripted details, trying to decipher them and the required inputs, effectively blunts your ability to observe beyond the instruction set you are executing. Another Paul story – Paul had been testing for only a short while (maybe two years) but was getting a reputation for finding important bugs. In a conversation with a developer one day, Paul was asked why this was so. Paul couldn’t answer the question at the time. Later, however, it dawned on him that those bugs were “off script”. They were the result of observing unusual outcomes or thinking about things the specification didn’t cover.

You need to be able to organize your testing in a way that is most optimal.

This statement, while not being completely clear to us in terms of its meaning, is problematic because for one thing it seems to assume there is an optimal order for testing. So then we need to consider, optimal for whom? Optimal for the tester, the development team, the Project Manager, the Release Manager, the C level business strategy or the customer?

If we adopt a risk-based focus (and we should) then we can have a view about an order of execution but until we start testing and actually see what the system is doing, we can’t know. Even in the space of a single test our whole view of “optimal” could change, so we need to remain flexible enough to change our direction (and re-plan) as we go.

Documenting all the different flows and combinations will help you identify potential areas that might otherwise be missed.

While it might seem like writing detailed test cases would help testers identify gaps, the reality is different. Diving into that level of detail, and potentially delaying your opportunity for hands-on testing, can actually help to obfuscate problem areas. Documenting the different flows and combinations is a good idea, and can form part of a good testing approach, but this should not be conflated with a reason for writing detailed test cases.

The statement suggests to us an implication that approaches other than detailed test cases will fail to detect issues. This is another statement that is made without any supporting evidence. It is also a statement that contradicts our experience. In simple terms, we posit that problems are found through discussion, collaboration and actual hands on testing of the code. The more time we spend writing about tests we might execute, the less time we have to actually learn the system under test and discovering new risks.

We also need to be careful to avoid the fallacy of completeness in saying “documenting all the different flows and combinations”. We all know that complete testing is impossible for any real-world piece of software and it’s important not to mislead our stakeholders by suggesting we can fully document in the way described here.

Summing up our views

Our experience suggests that visual options, such as mind maps, are less heavy and provide easier visual communication to stakeholders than a library of detailed test cases. Visual presentations can be generated quickly and enable stakeholders to quickly appreciate relationships and dependencies. Possible gaps in thinking or overlooked areas also tend to stand out when the approach is highly visual. Try doing that with a whole bunch of words spread across a table.

Our suggestions for further reading:

Thanks to Brian Osman for his review of our blog post.

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