TDD – A Fifth School of Software Testing

Bret Pettichord has a presentation on the Four Schools of Software Testing. He covers the schools of testing identified by Cem Kaner, James Bach and himself: Analytic, Factory, Quality and Context-Driven. (For a brief time, Bret had renamed “Factory” school to the “Routine” school, but has since reverted back to “Factory”.) This breaking down of popular testing ideas into schools is a thought-provoking concept, and just reading his presentation notes should get testers thinking about what they do on projects. “What school do I identify with?” a reader might ask themselves.

Cem Kaner has identified Test-Driven Development as another school of software testing. He talks about TDD as a big force in software development from the past decade in this paper: The Ongoing Revolution in Software Testing. On the context-driven testing mailing list, Cem Kaner explained why he identifies TDD as a testing school:

…TDD isn’t completely inside my [schools of software testing] paradigm. At [this] point, I ask:

(a) Is it coherent enough, popular enough, and looked to for guidance–a foundation for teaching about testing– enough to be called a school?

I think this is a clear yes. The fact that courses in TDD exist and are fashionable demonstrates that it’s a source of knowledge, inspiration, and guidance (which is at the essence of what I think of in a school). And there’s clearly an active group of collaborators who jointly develop and push the ideas.

(b) Is it testing?

It’s not inconsistent with my definition of testing, and a lot of people who advocate it think it is testing. OK, I accept it as testing.

Is it a unified field theory of testing? No. But neither is anything I’ve done. TDD focuses on problems that many of us haven’t focused on before, and sheds remarkably little light (or interest) on problems that many of us take very seriously. To the extent that it thinks its problems are the primary interesting problems, it asserts itself as a paradigm–elucidates some key issues and puts on blinders with respect to the rest. But I have my own blinders, so the mere fact that TDD is blind to some of the problems I find most interesting can’t be a basis for invalidating it as a school of testing. It can only be a basis for rejecting it as the driving philosophy of my school of testing.

Along with techniques, TDD advocates often espouse a set of values, a set of broader ideas about development, an attitude about people and how they should use their time and how they should be held accountable, an attitude about the use of tools, about the types of skills people doing this work should possess and how they should/could grow them–for sure, these are fuzzy sets, not everybody adopts all of them. It’s all of this stuff that separates schools — it’s also this type of stuff that gives context/interpretation for the use of the tools/techniques and the directions of advancement of the use and enhancement of these tools/techniques.

I think these illustrate an approach to testing that includes some deep and careful thinking, a rich set of practices, and attention to a lot of basic issues. I think I see different answers than I would expect from the factory school. I think it is much more brain-engaged than factory school, and much more about the cognition of the test creator than about the detail of procedures to be followed by the test runner.

So, I see a thoughtful, coherent view. A lot of practitioners. A body of work and advocates that guide thinking, practice and the teaching of thinking about how to envision, research, and practice testing. Looks like a school to me. And a welcome one.”

(posted with permission)

I agree with what he has said. In my own forays into pair testing with test-driven developers and learning how to do TDD from skilled practitioners, I have met people who are really dedicated to testing. They tend to seek out conventional testers who are also passionate about testing. This intersection of schools can sometimes have some confusing results at first.

I’ve witnessed confusion when conventional testers and TDD testers are working together. That prompted a blog post on vague words used in testing. Those I would characterize as Quality school testers often feel responsible for the TDD process and unit tests even though they aren’t programmers and haven’t tried TDD themselves. I have heard of TDD testers and Quality school testers attending the same meeting, using the same language, agreeing to move forward together, and then independently moving in completely different directions. In one case, a TDD developer and I spent several sessions where I “translated” the language that the Quality school folks were using. He started changing his use of the shared terminology by using synonyms to improve communication and reduce confusion. They managed to work things out reasonably well.

Is it helpful to make distinctions of testing schools like this? Here is one area where it certainly helps: when communicating testing concepts. When a word can mean different things depending on how a practitioner defines their role, it helps to understand where they are coming from. Cem Kaner has provided further insight on TDD, and we can use that to enhance our communication and collaboration with developers who are honing their own testing craft.