I've recently started to attend Extreme Wednesday sessions in the Filmhouse Cafe on Wednesdays. When I got back home after last night's session, Jenny asked how was the "Nerd Club Meeting". Well this is how it went. We had two separate goes at a simple web app to record expenses and payments, based on the spreadsheet I use to track my expenses. There were two pairs: Abdel and Jordon, Andy and I. Colin and John joined later. Getting started - Story Independence Trying to define the stories and acceptance tests was a useful exercise. We had trouble defining tests for "action" stories (eg add expense) without any view stories to verify the action had taken place: we combined an action and view story to get started. Ok, that seems obvious now but I really need to try these things to get a feel for them - reading books (eg Mike Cohn's) is not enough. Upfront Design vs The Simplest thing and Emergent Design Abdel and Jordon invested a small amount of time in defining a domain model. Andy and I had decided to go for what we thought was the simplest thing: a service that interacts directly with the database. We didn't get that for, through spending too much time discussing other things (Andy is so knowlegeable that it'd be a waste not to). Although by the end of the session we both thought our approach was the best - I've changed my mind. We were concentrating on an "enter" action: by the time we'd got to the "query" actions we would have probably needed to introduce some kind of DTO or swap to a domain model; the "simplest thing" was probably (in the end) a domain model. It's dangerous to draw conclusions from simple exercises, but maybe a small amount of upfront design is no bad thing. In reality I find it almost impossible not to think ahead when doing real work. I suppose the key practices are to delay over-commiting to a design until it is tried and proven; even then be prepared to change the design in the face of changing requirements, complexity, and knowledge.

Thursday, January 13, 2005 | Permalink | 0 Comments