I forget exactly when, but I think it was 2008 or 2009. Anyway, I was at a software conference, and I was chatting with a developer after one of the sessions about cool new technologies and stuff. I don’t remember what hot new thing it was we talked about, all I remember, is the shoes he was wearing!
This is rather an unusual style of running shoe. At the time, I’d never seen any like this before, and I was intrigued. It turns out that this developer I was talking to was, like me, also something of a serial early adopter, it’s just that he not only picked up shiny new programming tools and technologies.
At the time, I was running in a pair of shoes with thick heel padding the shop assistant had assured me would correct my bad posture and foot “pronation”. This guy’s “five finger” shoes had none of that, in fact quite the opposite. I was looking at disruptive running technology.
The conversation quickly switched from the latest programming tools and frameworks, as this guy explained the essential benefits of his shoes:
- Your toes can spread out, giving better push-off from the ground
- Thin sole – you adapt your stride to the surface because you can feel it
- No heel padding, means you strike the ground with the whole foot simultaneously.
And of course, most importantly for a technology enthusiast:
- People stare at you feet!
Following this conversation, a little googling about and watching the odd video by a “running style expert”, I became convinced. To be honest, it wasn’t much contest – shiny new technology, being in with the cool kids – I bought some new shoes, with toes and everything!
It took me several weeks to get used to them. You have to start with short distances, build up some new muscles in your foot, and learn to strike the ground with the whole foot at once. In my old shoes, I had a tendency to strike heel-first, because of the huge wad of padding on the sole, but in these minimal shoes, that just hurt. It was useful feedback, the whole-foot-at-once gait is supposed to be better for your knees.
After a few weeks of running shorter distances, slower than before, I gradually found my stride, and really started to enjoy running my usual 7km circuit of the local forest, in my eye-catching five-fingered shoes.
Unfortunately it didn’t last. Maybe two or three months later something happened. I think the technical term for it is Swedish Autumn. It turns out that forest tracks gain a surprising number of cold, muddy puddles at that time of year! Shoes with a very thin sole that isolate and surround each individual toe in waterlogged fabric, mean absolutely freezing feet 🙁
So I’m back on the internet, looking for new, shiny technology to fix this problem, and of course, I buy some new shoes. This time I got a pair of minimalist shoes in waterproof goretex, with basically all the features of my old shoes, minus the individual toes.
I was back out on the forest track, faster than ever, with dry, comfortable feet – win! The only problem was, people were no longer staring at my eye-catching toes. So you can’t have it all!
So this is normally a blog about programming. What’s going on?
Test Driven Development as a Disruptive Technology
I’ve been thinking about this, and it seems to me that as with running shoes that have toes, TDD is something of a disruptive technology. Just as I haven’t seen the majority of runners switch to shoes with toes, I also havn’t seen the majority of developers using TDD yet. Neither seem to have crossed Geoffrey Moore’s “chasm”.
Lots of developers write unit tests, but I think that’s slightly different. I’m talking about a TDD where developers primarily use tests to inform and direct design decisions, and rely on them for minute-by-minute feedback as they work. In 2009, Kent Beck made an observation in his blog that “the data suggests that there are at most a few thousand Java programmers actively practicing TDD”. I don’t think the situation is radically different today.
So can we learn anything about TDD from the story about running shoes? A couple of points I find relevant:
- Early adopters will try a new technology based on really very flimsy evidence, and will persevere with it, even if it slows them down in the short term.
- Early adopters like to look cool and stick out.
You may think that last point is just vanity, but actually, being a talking point helps drive adoption, but primarily amongst other, similarly minded technology geeks.
I remember a while back I was at work, writing some code, when a guy from another team came over to ask me something. He was about to leave, when he did a double-take and stared at my screen for a moment. “Are you doing TDD? I’ve never seen anyone actually do that in production code. Do you mind if I watch?”. So, you see, eye-catching shiny new technology, and I’m one of the cool kids, about to be emulated by the guy in the next team. 🙂
The other part of this story, is of course the compromise I made when the cool technology met the reality of a muddy Swedish forest track. The toes went, but the shoe I ended up with is still radically different from the one I had before. I think that for TDD to reach the mainstream, it may need to become a little less extreme, a little more practical – but without losing the essential benefits.
What are the essential benefits of TDD? Well, I would say something like this:
- Design: useful feedback, pushing you away from long methods and tightly-coupled classes, because they’re hard to test.
- Refactoring: quickly detecting regression when you make a mistake
- Productivity: helping you to manage complexity and work incrementally
So is it possible to get these things in another way? Without driving development minute-by-minute with tests? Well, that’s probably the subject of another blog post…
You might be interested to watch a video of my recent keynote speech at Europython, where I told this story.