Thursday, 3 September 2009

First JDojo@Gbg meeting

A little while ago we had the first meeting of our new coding dojo here in Göteborg. We are focussing on learning Test Driven Development using Java and Eclipse. I was very encouraged that two of my colleagues, Fredrik and Martin, volunteered to help organize the group. There was actually quite a lot of interest generally, and we filled all 12 places and even have a (small) waiting list. I didn't want the group to grow too big, since the dojo style of learning should be quite participatory, and the time slot is only 2 hours. Everyone should get a chance to be heard, and to take the keyboard.

At the meeting I introduced the dojo concept with a set of slides I have used before. At dojo meetings our focus should be on deliberate practice, aquiring good coding habits, mutual encouragement and feedback.

We then took on KataFizzBuzz which went very smoothly. I started by introducing the Kata, using this picture of the "teacher" pointing at you, asking you to say the next number in the FizzBuzz sequence. She is sufficiently scary looking that you definitely need to write a program to print a FizzBuzz cheat sheet before the next lesson!

I also introduced something I havn't done before at a dojo meeting - starting with some code rather than a blank editor. I had the acceptance test for the Kata already coded up and failing. When I practiced this Kata I realized the hardest part was writing the acceptance test, which captures the sequence that is written to System.out. I could have begun the meeting by written it in front of the audience, but I really wanted to get them coding, not just watching me.

Martin wrote the first unit test, fizzbuzz(1) -> [1] and I noticed that his style is slightly different from mine. He fixed all the compiler errors as he went along, whereas I would tend to leave them all until I finish the test, or at least until I want to run it. Maybe that is because he has worked in Java/Eclipse longer than me, and that is the way Eclipse likes you to work. Anyway, I then implemented the code to make the test pass (fake it!) and wrote the next test fizzbuzz(2) -> [1,2]. So then he had to write just enough code to make it pass (a simple loop).

Then we handed the keyboard to two members of the audience, and Martin and I sat down in their chairs, and the Randori was really underway. We continued with this pair and two others using this ping-pong style until after about an hour we had completed the first part of the Kata - printing out the basic fizzbuzz sequence up to 100.

I suggested that the pair at the front try to run the acceptance test, which they did, and it failed. The reason was that the unit tests had been testing an internal method fizzbuzz() and the acceptance test checked that when you call main() you get the right sequence written to System.out. It was at this point I wondered if I had made the right decision when I wrote the acceptance test in advance, since that meant the guy at the keyboard clearly didn't really understand what it was for. His first thought of how to make it pass was to change it to call fizzbuzz() instead of main(), until I stopped him - "No! don't change the test! Fix the code!". I felt like I was rapping him over the knuckles with a ruler (something I am thankful my Maths teacher never did).

Towards the end of the meeting so we held a 10 minute retrospective. People seemed cautiously positive towards TDD and the dojo in general, but I think they maybe still getting used to the format and working out whether it is "ok" to be openly critical. I hope for more dissent, discussion and group learning next time.

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