On the Value of Test Cases


Something is rotten in the state of Denmark.

William Shakespeare – Hamlet

Over the period of a couple of weeks, I was able to observe the usage of test cases in a software development project. The creation of test cases was started at the moment when the functional specifications were declared to be relatively crystallized. The cases were detailed in specific steps and entered into a test management tool, in this case HP Quality Center. They’d be reviewed, and in due time executed and the results would be reported to the project management.

During these weeks after the finalization of the functional specifications, not a lot of software was actually built, so the testers involved in the project saw the perfect chance to prepare for the coming release by typing their test cases. They believed that they had been given a blissful moment before the storm, in which they would strengthen their approach and do as much of the preparatory work as they could, in order to be ready when the first wave of software would hit. Unfortunately, preparation, to these testers, meant the detailed specification of test cases for software changes that still had to be developed, a system that was partly unknown or unexplored by them, and functional specifications that proved to be less than ready.

There is no need to guess what happened next. When eventually software started coming down the line, the technical implementation of the changes was not quite as expected, the functional specifications had changed, and the project priorities and scope had shifted because of new demands. It was like the testers had shored up defenses to combat an army of foot soldiers carrying spears and they were now, much to their surprise, facing cannons of the Howitzer type. Needless to say, the defenders were scattered and forced to flee.

It is easy to blame our software development methods for these situations. One might argue that this project has characteristics of a typical waterfall project and that the waterfall model of software development invites failure. Such was argued in the 1970s (PDF, opens in new window). But instead of blaming the project we could ask ourselves why we prepare for software development the way we do. My point is that by pouring an huge amount of energy into trying to fixate our experiments in test cases (and rid them of meaning — but that’s another point), we willingly and knowingly move ourselves into a spot where we know we will be hurt the most when something unexpected happens (see Nassim Nicholas Taleb’s Black Swan for reference). Second of all, I think we seriously need to reassess the value of drawing up test cases as a method of preparation for the investigation of software. There are dozens of other ways to prepare for the investigation of software. For one, I think, even doing nothing beats defining elaborate and specific test cases, mainly because the former approach causes less damage. It goes without saying that I do not advocate doing nothing in the preparation for the investigation of software.

As a side note, among these dozens of other ways of preparing for the investigation of software, we can name the investigation of the requirements, the investigation of comparable products, having conversations with stake holders, having conversations with domain experts or users, the investigation of the current software product, the investigation of the history of the product, the reading of manuals etc… An excellent list can be found in Rikard Edgren’s Little Black Book on Test Design (PDF, opens in new window). If you’re a professional software tester, this list is not new to you. What it intends to say is that testers need to study in order to keep up.

Yet the fact remains that the creation of test cases as the best way to prepare for the investigation of software still seems to be what is passed on to testers starting a career in software testing. This is what is propagated in the testing courses offered by the ISTQB or, in the Netherlands, by TMap. This approach should have perished long ago for two reasons. On the one hand, and I’ve seen this happen, it falsely lures the tester in thinking that once we’re done specifying our test cases, we have exhausted and therefore finalized our tests. It strengthens the fallacy that the brain is only engaged during the test case creation ‘phase’ of the project. We’re done testing when the cases are complete and what remains is to run them, obviously the most uninspiring part of testing.

The second thing I’ve seen happening is that test case specification draws the inquiring mind away from what it does best, namely to challenge the assumptions that are in the software and the assumptions that are made by the people involved in creating the (software) system — including ourselves. Test case creation is a particular activity that forces the train of thought down a narrowing track of confirmation of requirements or acceptance criteria, specifically at a time when we should be widening our perspectives. By its focus on the confirmation of what we know about the software, it takes the focus away from what is unknown. Test case creation stands in the way of critical thinking and skepticism. It goes against the grain of experimentation, in which we build mental models of the subject we want to test and iteratively develop our models through interaction with the subject under test.

mcl82If there is one thing that I was forced to look at again during the last couple of weeks — during which I was preparing for the testing of software changes — it was the art of reasoning and asking meaningful questions. Though I feel confident when asking questions, and though I pay a lot of attention to the reasoning that got me to asking exactly that particular set of questions, I also still feel that I need to be constantly aware that there are questions I didn’t ask that could lead down entirely different avenues. It is possible to ask only those questions that strengthen your assumptions, even if your not consciously looking for confirmation. And very much so, it is possible that answers are misleading.

So for the sake of better testing, take your ISTQB syllabus and — by any means other than burning — remove the part on test cases. Replace it with anything by Bacon, Descartes or Dewey.

“Criticism is the examination and test of propositions of any kind which are offered for acceptance, in order to find out whether they correspond to reality or not. The critical faculty is a product of education and training. It is a mental habit and power. It is a prime condition of human welfare that men and women should be trained in it. It is our only guarantee against delusion, deception, superstition, and misapprehension of ourselves and our earthly circumstances. Education is good just so far as it produces well-developed critical faculty. A teacher of any subject who insists on accuracy and a rational control of all processes and methods, and who holds everything open to unlimited verification and revision, is cultivating that method as a habit in the pupils. Men educated in it cannot be stampeded. They are slow to believe. They can hold things as possible or probable in all degrees, without certainty and without pain. They can wait for evidence and weigh evidence. They can resist appeals to their dearest prejudices. Education in the critical faculty is the only education of which it can be truly said that it makes good citizens.”

William Graham Sumner – Folkways: A Study of Mores, Manners, Customs and Morals