Delete Your Code

Wednesday 24 July 2013 at 17:53 BST

That was my battle cry at Palantir's first ever code retreat.

Last weekend, we spent two and a half days out in the beautiful English countryside on some of the hottest days of the year so far. The agenda was as follows: Friday afternoon was to be dedicated to TDD, a code retreat was held on Saturday, and on Sunday, we held our least hacky "hackday" ever.

Thanks so much to Adrian Bolboaca for helping plan the first two days of this event, and to my colleagues Huw, Joe and Michael for organising the event and the venue.

Level 1: TDD

We started with an introduction to test-driven development, partially historical, but mostly practical. I wrote the simplest test I've ever written:

@Test public void
says_hello_to_the_entire_world() {
    Hello hello = new Hello();
    assertThat(hello.world(), is("Hello, world!"));
}

And proceeded to make it pass. (This is left as an exercise for the reader.) After a few more iterations on this, implementing hello.to("Bob"), the group of ten was ready to try to write tests, some for the first time. I kicked them off with the Anagram kata and watched them work, occasionally dipping in to offer advice. Because people were arriving throughout the day, most of my time was spent redoing my "Hello, world!" demonstration.

Obviously, as newbies to the genre, there were a lot of misconceptions, and people had a really hard time writing the simplest possible code to make their tests pass. On the other hand, we had some real wins, most notably in people discovering the need for other kinds of testing disciplines. Some found the desire to write outside-in tests (even acceptance tests, in one case) before going too low-level, and a couple more essentially reinvented property-based testing.

And then we went and had some drinks and a good night's sleep. Tiredness kills, and I was planning on tiring everyone out tomorrow.

Level 2: The Code Retreat

I've blogged extensively about code retreats and legacy code retreats before, but there were some notable differences between this one and the others in which I've participated or facilitated. They were mostly due to the inexperience of the attendees, resulting in a retreat that was much more of a teaching exercise than is usual. I'm glad to say that most of the teaching was still done between pairs, though, which is always the result I'm looking for in an event like this. As with other code retreats I've run, the kata used was Conway's Game of Life, and sessions were 45 minutes long.

The morning gave way to a large amount of frustration as people had to un-learn the habit of churning out code without too much thinking about design and scope. Palantir is full of developers who can crank out a million lines of code a day, so getting them to slow down and not worry about being too productive was pretty difficult. After a few sessions, people were starting to get into the habit of writing The Simplest Thing That Could Possibly Work™, and so over lunch, I started scheming on how to mess with their brains a little more.

A delicious meal gave way to session four, in which I gave a demonstration of test doubles and the differences between stubs and mocks, as well as explaining the difference between Classic TDD and the "London School". I then told everyone to go and develop a solution to the kata from the outside-in, using mocks to drive the design of their application. There was a lot of head-scratching, and no one came away with much code, but the seed of top-down development was planted.

The last two sessions were designed to completely blow people's minds and really show them why TDD is useful, as well as teaching them some new tricks. I used Adi and Erik's baby steps idea to get people hyperactive, and then dropped Jeff Bay's object calisthenics on them to round off the day with something really thought-provoking. Both of these sessions went down really well—I think that for the first time, things really became challenging for everyone. Object calisthenics really emphasises the need for outside-in design, as it firmly forbids breaking state encapsulation, which I think helped people understand the need for that approach to software design and TDD.

Finally, just to show off, I demonstrated how a decent implementation that follows the rules of object calisthenics can be actually quite beautiful.

The feedback was overwhelmingly positive. Except for the limit on the drinks, because people are alcoholics alcohol is a human right we're pretty spoilt.

Level 3: (Not a) Hackday

Because everyone loves hackdays, we had one. Except this was a hackday with a twist: no hacking allowed. Pair programming was mandatory and not testing was punishable by being locked in a dark box and having your drinks taken away.

With one exception, people worked on new projects or standalone features—we hadn't covered testing legacy code, and I don't think anyone was really in the mood to spend a Sunday banging their heads against walls. We worked on a bunch of cool things, but by far my favourite was the beginnings of a testing framework for an in-house proprietary language, spearheaded by the guy who was initially very much against writing tests. I think it's safe to say he's thoroughly converted.

All in all, great success. I'm really glad that everyone discovered the main lessons of the whole weekend: that tests really don't slow you down, and you learn faster by pairing than by any other method I've found.

Oh, and the drinks and the weather were sublime.