Monday, April 06, 2015

Unit Testing Points of View, Probably

Michael Feathers, Brian Marick, and I are collaborating to create a new book: Unit Testing Points of View ... probably.


In 2014 Martin Fowler provided Technical Review for Working Effectively with Unit Tests. As part of his feedback he said something along the lines of: I'm glad you wrote this book, and I'll likely write a bliki entry noting what I agree with and detailing what I would do differently. I'm still looking forward to that entry, and I think the idea is worth extending beyond Martin.

Unit testing is now mainstream, has tons of entry level books, and has a great reference book. The result is a widely accepted idea that you can quickly and easily adopt; unfortunately, I've found little in the way of documenting pattern trade-offs. I believe that combination leads to a lot of waste. To help avoid some of that waste, I'd like to see more written about why you may want to choose one Unit Testing style over another. That was the inspiration and my goal for Working Effectively with Unit Tests. Growing Object-Oriented Software is another great example of a book that documents both the hows and whys of unit testing. After that, if you're looking for tradeoff guidance... good luck.

Is this a problem? I think so. Without discussion of tradeoffs, experience reports, and concrete direction you end up with hours wasted on bad tests and proclamations of TDD's death. The report of TDD's death was an exaggeration, and the largest clue was the implication that TDD and Unit Testing were synonymous. To this day, Unit Testing is still largely misunderstood.

What could be

Working Effectively with Unit Tests starts with one set of opinionated Unit Tests and evolves to the types of Unit Tests that I find more productive. There's no reason this evolution couldn't be extended by other authors. This is the vision we have for Unit Testing Points of View. Michael, Brian, and I began by selecting a common domain model. The first few chapters will detail the hows and whys of how I would test the common domain model. After I've expressed what motivates my tests, Brian or Michael will evolve the tests to a style they find superior. After whoever goes second (Brian or Michael) finishes, the other will continue the evolution. The book will note where we agree, but the majority of the discussion will occur around where our styles differ and what aspect of software development we've chosen emphasize by using an alternative approach.

Today, most teams fail repeatedly with Unit Tests, leading to (at best) significant wasted time and (at worst) abandoning the idea with almost nothing gained. We aim to provide tradeoff guidance that will help teams select a Unit Testing approach that best fits their context.

As I said above: There's no reason this evolution couldn't be extended by other authors. In fact, that's our long term hope. Ideally, Brian, Michael and I write volume one of Unit Testing Points of View. Volume two could be written by Kevlin Henney, Steve Freeman, and Roy Osherove - or anyone else who has interest in the series. Of course, given the original inspiration, we're all hoping Martin Fowler clears some time in his schedule to take part in the series.

Why "Probably"?

Writing a book is almost always a shot in the dark. Martin, Michael, Brian, and I all think this a book worth writing (and a series worth starting), but we have no idea if people actually desire such a book. In the past you took the leap expecting failure and praying for success. Michael, Brian, and I believe there's a better way: leanpub interest lists (here's Unit Testing Points of View's). We're looking for 15,000 people to express interest (by providing their email addresses). I'm writing the first 3 chapters, and they'll be made available when we cross the 15k mark. At that point, Michael and Brian will know that the interest is real, and their contributions need to be written. If we never cross the 15k mark then we know such a book isn't desired, and we shouldn't waste our time.

If you'd like to see this project happen, please do sign up on the interest list and encourage others to as well (here's a tweet to RT, if you'd like to help).