As I’ve coached software engineering teams on testing practices I’ve found that often the obstacle is not whether they believe they should test or whether they understand the concepts of testing, but the concrete understanding of what testable code looks like and knowledge of the implementation patterns of how to bring code under test.

Looking around, I realized that no one had written squarely on this topic. There are lots of great books by the likes of Bob Martin, Michael Feathers, Lasse Koskela, Kent Beck, Steve Freeman and Nat Pryce, Martin Fowler, Joshua Kierevsky, and others that address approaches to testing, the importance of testing, and so forth. In the process they show techniques for bringing code under test, but it’s usually secondary to the points being made. The only exception to this is Michael Feathers’ “Working Effectively with Legacy Code” but it has a very specific focus that necessarily limits the techniques discussed.

Many of the examples of the book are in Java, although overall I use a dozen or so languages for examples. This is largely an artifact of the language I was most immersed in when the seed of the idea was planted. There are many examples from JavaScript, including one of the worked example chapters. With a few exceptions that I tried to point out, almost all of the techniques can be applied in most languages with only a little adaptation, so if Java and JavaScript are not your primary tools, you should still be able to leverage the techniques.

Happy testing!