When Do We Stop Testing? One More Sure Thing

Not too long ago, I posted a list of stopping heuristics for testing. As usual, such lists are always subjective, subject to refinement and revision, and under scrutiny from colleagues and other readers. As usual, James Bach is a harsh critic (and that’s a compliment, not a complaint). We’re still transpecting over some of the points; eventually we’ll come out with something on which we agree.

Joe Harter, in his blog, suggests splitting “Pause That Refreshes” into two: “Change in Priorities” and “Lights are Off“. The former kicks in when we know that there’s still testing to be done, but something else is taking precedence. The latter is that we’ve lost our sense of purpose—as I suggested in the original post we might be tired, or bored, or uninspired to test and that a break will allow us to return to the product later with fresh eyes or fresh minds. Maybe they’re different enough that they belong in different categories, and I’m thinking that they are. Joe provides a number of examples of why the lights go out; one feels to me like “customary conclusion”, another looks like “Mission Accomplished”. But his third point is interesting: it’s a form of Parkinson’s Law, “work expands to fill the time available for its completion”. Says Joe, “The test team might be given more time than is actually necessary to test a feature so they fill it up with old test cases that don’t have much meaning.” I’m not sure how often people feel as though they have more time than they need, but I am sure that I’ve seen (been in) situations where people seem to be bereft of new ideas and simply going through the motions. So: if that feeling comes up, one should consider Parkinson’s Law and a Pause That Refreshes. Maybe there’s a new one there. But as Joe himself points out, “In the end it doesn’t matter if you use [Michael’s] list, my list or any list at all. These heuristics are rules of thumb to help thinking testers decide when testing should stop. The most important thing is that you are thinking about it.”

For sure, however, there is a glaring omission in the original list. Cem Kaner pointed it out to me—and that shouldn’t have been necessary, because I’ve used this heuristic myself. It focuses on the individual tester, but it might also apply to a testing or development team.

Mission Rejected. We stop testing when we perceive a problem for some person—in particular, an ethical issue—that prevents us from continuing work on a given test, test cycle, or development project.

Would you continue a test if it involved providing fake test results? Lying? Damaging valuable equipment? Harming a human, as in the Milgram Experiment or the Stanford Prison Experiment? Maybe the victim isn’t the test subject, but the client: Would you continue a test if you believed that some cost of what you were doing—including, perhaps, your own salary—were grossly disproportionate to the value it produced? Maybe the victim is you: Would you stop testing if you believed that the client wasn’t paying you enough?

The consequences of ignoring this heuristic can be dire. Outside the field of software testing, but in testing generally, a friend of mine worked in a science lab that did experiments on bone regeneration. The experimental protocol involved the surgical removal of around one inch of bone from both forelegs of a dog (many dogs, over the course of the research), treating one leg as an experiment and the other as a control. Despite misgivings, my friend was reasonably convinced of the value of the work. Later, when he found out that these experiments had been performed over and over, and that no new science was really being done, he suffered a nervous breakdown and left the field. Sometimes testing doesn’t have a happy ending.

4 replies to “When Do We Stop Testing? One More Sure Thing”

  1. I like to Go over two things, ‘Change in Priorities’ and ‘Lights off’. Glad it comes from a experienced 🙂

    Michael replies: Nice suggestions. I’ve incorporated “change tack” into the list since the post was written, and “lights off” is to me like “mission abandoned”. But I’m delighted that you seem to have developed a list of your own. It’s important that each of us owns his testing models.


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