There’s a one day domain-driven design event happening at SkillsMatter this Friday, 19 June in London. I’m not speaking this time so I get to sit back and enjoy some talented folks talking about really applying DDD rather than just theoretical stuff.
It’s finally happening - I’m writing a book! Well ok, the remarkable David Chelimsky is writing a book. It’s called Behaviour Driven Development with RSpec, Cucumber and Friends and myself and a few other folks are contributing in varying degrees.
…or why Mockito is my new friend.
Back in 2003 I started work on a framework called JBehave. It was an experiment to see what JUnit might have looked like if it had been designed from the ground up for TDD rather than as a unit testing framework. I was also starting to use the phrase “behaviour-driven development” to describe what I meant. The jbehave.org domain was registered and the first lines of code written on Christmas Eve 2003, much to my wife’s bemusement. Over time JBehave grew a much more interesting aspect in the form of a framework for defining and running scenarios, or automated acceptance tests.
So it’s that time of year again. I’ve got a number of conferences and workshops coming up, ranging over all sorts of topics. I just popped over to Martin Fowler’s site (I’m doing a talk with him this week) and noticed that he has a much more organised setup than me. All his events are in a sidebar and there is a handy link if you want more details. Another idea to go on my to-do pile.
Earlier this year I wrote an article to introduce service-oriented architecture to non-technical people. It was published in the May 2007 issue of Better Software magazine.
The kind folks at Better Software have allowed me to provide a PDF version of the article, complete with retro 1950s graphics. You can also read it as a single html page.
Please post any comments here, because I’ve disabled comments on the page itself.
It turns out that having a day job can play havoc with your blogging activities. I’m posting a round-up of recent activities, in no particular order, with the intention of expanding on each of these topics in the coming weeks. But we all know what happens to intentions.
This is mostly a brain dump to make me feel guilty enough to write some of it up, so feel free to skip it if you’re busy. That FaceBook page isn’t going to update itself you know.
RBehave is a framework for defining and executing application requirements. Using the vocabulary of behaviour-driven development, you define a feature in terms of a Story with Scenarios that describe how the feature behaves. Using a minimum of syntax (a few “quotes” mostly), this becomes an executable and self-describing requirements document.
BDD has been around in the Ruby world for a while now, in the form of the excellent RSpec framework, which describes the behaviour of objects at the code level. The RSpec team has focused on creating a simple, elegant syntax and playing nicely with other frameworks, in particular Rails and the Mocha mocking library.
At a recent software architecture workshop, I was discussing the ideas behind BDD with a great group of people (more about that soon). One theme that kept coming up was the fact that I needed to write much more about BDD as an entire methodology, and to address the current perception that it is just a repackaging of test-driven development (which, to be fair, is where it started).
As I was describing the workings of BDD, I discovered that I had made the assumption that everyone knew what a Story was, in the agile sense of defining a requirement. It turns out that there’s a whole world outside of my little bubble that use all sorts of different processes for identifying and defining requirements, and in particular they don’t know what I mean by a Story, nor why they should care.
At the beginning of this year I wrote a feature article for Better Software magazine, which was published as “Behavior Modification” back in March.
The article is now available on my site. It gives an overview of behaviour-driven development, from its origins as a coaching aid for TDD through to its current form as a proven, comprehensive development approach.
Behaviour-driven development started life as an NLP exercise to stem the abuse of the word “test” in “test-driven development”. Since then it has grown into a respectable and proven agile methodology (with a small “m” of course).
Dave Astels, the award-winning author, was an early adopter of BDD and has been instrumental in raising its profile. He presented it at Canada on Rails and is taking it to JAOO and SD Best Practices. He has even presented it to Google. His Ruby BDD framework, rspec, has inspired a number of similar projects.
This question came up at the recent Expo-C conference, when presenter Michael Stal talked about designing services to be “as simple as possible but no simpler”. Kent Beck advises us to do “the simplest thing that could possibly work”, but this is often mistaken for “the first thing I could possibly think of” or even “the only thing I know” (also known as the Golden Hammer antipattern).
We picked up the topic as an open space session later that day. I took the position that you should only ever focus on the specific case in hand, and then only generalize if you meet another similar case. Erik Meijer, the reknowned language guru and thoroughly nice guy, took the opposing stance that you should abstract the general solution and then implement it locally. He pointed out that this was an approach with centuries of mathematical tradition behind it and is a fundamental tenet of modern functional programming1. This developed into a good-natured but heated stand-off. I just couldn’t see the value of building a fancy general solution on the client’s money, when there was lots more important work to do and limited time. He couldn’t understand why you wouldn’t take the effort to make something as flexible as possible for the end user, especially if you were designing something like a programmers’ toolset or language. On the scale of specific to general—or concrete to abstract—we were at opposite ends, with a seemingly intractable chasm between us. He was simply wrong, and so, of course, was I.
From the session summary
The Ruby language has taken the development world by storm. Its combination of clean, object-oriented syntax (everything is an object) coupled with Perl-like platform independence and inline text processing power make it a useful tool both for writing small utilities and as a rapid prototyping language. The popular web framework, Ruby-on-Rails, allows for easy development of highly-functional web applications.
This session will explore these aspects of Ruby, namely for utilities, prototyping and web development. We will also discuss issues such as scalability and deployment.??
I was lucky enough to attend the Software Architecture Workshop in Cortina recently. It was a three day workshop based around the idea of Open Spaces, which involves handing the asylum keys to the inmates and seeing what happens.
I convened a session called “What’s so hard about Event-Driven Programming?” to explore the experiences of the other delegates in designing, implementing and testing asynchronous, event- or message-driven systems. I took the position that actually it was all very straightforward as long as you followed a few basic principles. Another delegate, Mats Helander, took the opposing view that asynchronous, event-based systems could develop scary emergent behaviour that would lead to a world of hurt.