It had been a long day, so a few of the fellows from the class agreed to meet a restaurant downtown. The main courses had been cleared off the table, some beer had been delivered, and we were waiting for dessert. Pedro (not his real name) was complaining, again, about how much time he had to spend doing administrivial tasks—meetings, filling out forms, time sheets, requisitions, and the like. “Everything … Read more
Calculating a ratio of passing tests to failing tests is a relatively easy task. If it is used as a means of estimating the state of a development project, though, the ratio is invalid, irrelevant, and misleading. At best, if everyone ignores it entirely, it’s simply playing with numbers. Otherwise, producing a pass/fail ratio is irresponsible, unethical, and unprofessional. A passing test is no guarantee that the product is working … Read more
Despite all of the dragons that Agile approaches have attacked successfully, a few still live. As crazy as it is, the idea of one test check per requirement has managed to survive in some quarters. Let’s put aside the fact that neither tests nor requirements are valid units of measurement, and focus on this: If you believe that there should be one test per requirement, then you have to assume … Read more
Let’s imagine, for a second, that you had a political problem at work. Your CEO has promised his wife that their feckless son Ambrose, having flunked his university entrance exams, will be given a job at your firm this fall. Company policy is strict: in order to prevent charges of nepotism, anyone holding a job must be qualified for it. You know, from having met him at last year’s Christmas … Read more
Eric Jacobson has a problem, which he thoughtfully relates on his thoughtful blog in a post called “How Can I Tell Users What Testers Did?”. In this post, I’ll try to answer his question, so you might want to read his original post for context. I see something interesting here: Eric tells a clear story to relate to his readers some problem that he’s having with explaining his work to … Read more
In response to my previous blog post “Another Silly Quantitative Model”, Greg writes: In my current project, the product owner has assumed the risk of any financial losses stemming from bugs in our software. He wants to release the product to customers, but he is of course nervous. How do you propose he should best go about deciding when to release? How should he reason about the risks, short of … Read more
John D. Cook recently issued a blog post, How many errors are left to find?, in which he introduces yet another silly quantitative model for estimating the number of bugs left in a program. The Lincoln Index, as Mr. Cook refers to it here, was used as a model for evaluating typographical errors, and was based on a method for estimating the population of a given species of animal. There … Read more
Yesterday I set up a thought experiment in which we divided our day of testing into three 90-minute sessions. I also made a simplifying assumption that bursts of testing activity representing some equivalent amount of test coverage (I called it a micro-session, or just a “test”) take two minutes. Investigating and reporting a bug that we find costs an additional eight minutes, so a test on its own would take … Read more
If you’re a tester, you’ve probably been asked, “Why is testing taking so long?” Maybe you’ve had a ready answer; maybe you haven’t. Here’s a model that might help you deal with the kind of manager who asks such questions. Let’s suppose that we divide our day of testing into three sessions, each session being, on average, 90 minutes of chartered, uninterrupted testing time. That’s four and a half hours … Read more
In the testing business, we’ve been wrestling with the measurement problem for quite a while. I think there are two prongs to the problem. The first is the aphorism that “you can’t control what you can’t measure”. The second is the confusion between measurement (which can be either quantitative or qualitative) and metrics, which are mathematical functions of measurements, and therefore fundamentally quantitative, only quantitative. I don’t know if you … Read more