Book review: Growing Object Oriented Software Guided by Tests

I’m a curious kind of guy. It is with some surprise, then, that I catch myself re-reading a technical book: Nat Pryce and Steve Freeman’s Growing Object Oriented Software Guided By Tests. It’s a very practical book, stuffed with code and useful advice, but it’s also more than that.

The first section of the book gives an overview of the basic principles of object-oriented design and test-driven development; not much is new but everything is clearly explained. The third and final section is a potpourri of test-centric techniques to identify problems and improve code quality. But the meat of the book is in the second section, a long walkthrough the development of a sample program. It’s a much larger example than usually found on programming books, tackling thorny issues such as asynchornous inter-process communication and end-to-end testing of GUIs. And it reads like a real software project, there are missteps, refactorings are rolled-back, some of the work is almost clerical, but then there are the great design breakthoughs, the elegant ideas that simultaneously solve several difficulties, the joy in seeing the product grow. It felt like reading a good novel. And that’s kind of what it is, a programming book that is a narrative, not an exposition. Besides making for a good read, the narrative aspect of the book is important for showing how modern object-orientation practice takes place.

OO criticisms nowadays are a dime a dozen, and though they sometimes present good points, often many of the arguments are directed at practices that aren’t so common, or at least that shouldn’t be so common. For instance, inheritance hierarchies, rampant mutable state, and patternitis (the FactoryFactory syndrome), are not indictments of object orientation, just symptoms of bad programming practice. One of the great things about GOOS is that it provides a great example of actual non-trivial object-orientation. And the same goes for test-driven-development, any abstract discussion of the benefits of TDD is bound to seem hand-wavey; this book helps to ground the understanding in real coding, done step by step in front of the reader’s eyes.

Anyway, I've read some pretty good technical books this year, but this one was the best.

Context, context, context

Joel Spolsky's latest diatrabe, and the outcry the blogosphere predictably issued, got me thinking about, well, about an old joelonsoftware article: Five Worlds. This one is a favorite of mine, maybe second only to the classic The Law of Leaky Abstractions. The point, in a nutshell, is that we too often forget the importance of context when discussing our trade.

I personally believe the Agile movement induced solid progress in software development teams worldwide, but we shouldn't forget where it came from: corporate software projects. Extreme Programming was born in a Chrysler project, it doesn't get much more corporate than this. Most of the signatures under the Agile Manifesto come from consultants, and again, is there anything more corporate that consultants?

This isn't meant to be a put-down of enterpresey work. I am myself a consultant and won't apologise for it. But it pays to look at the differences between the internal corporate projects world and the software product development world:

• Corporate projects tend to be wide: lots of forms gathering data, lots of reports spitting data out, huge ugly menus. Products are usually more focused, with fewer interaction points that are backed with more sophisticated logic.
• A consequence is that, while a developer for an internal corporate system might see any given screen a handful of times throughout the project, a software product developer can live inside the system almost as much as the end users (and so, catch more bugs).
• Corporate systems are expected to reproduce complicated real-life behavior. Tax codes and compliance requirements come to mind. Sounds boring, but at least there are clear expectations for what the correct functioning of the software should be. Another way to put it is that in these systems, it's feasible to anticipate putative bugs. In a product, on the other hand, there could be many undesirable characteristics that are impossible to precisely specify (say we're working on a game, and level 3 should be just a notch more difficult than level 2 but still much easier that level 4 - how would you precisely specify that?).
• First impressions are crucial for a product. A 1.0 dud can kill a startup - just think of Cuil. Not only it must work, it must be polished, discoverable and pretty. The incentive framework for internal products is very different; as long as the team delivers anything at all, even if almost useless, it's often possible to change course and steer the project towards the actual needs.

Reading these points, it seems that I'm justifying a lower standard of code quality in product development. I'm not. TDD really does allow you to go faster, I can't even fathom what would be like to code without refactoring every few seconds, and all the old sayings about how we spend much more time reading that writing code are true, regardless of how crucial is that we reach that 1.0 milestone.

I was desperatly trying to avoid this cliché, but I just couldn't resist. In the end, we should really try to learn from each other. Agile teams should spend more time thinking about the people who will live in their systems day-in-day-out, and product devs might have a thing or two to learn from the fast pace of a pair TDD-ing away.