The Art of Agile Development, 2nd Edition

Incremental Design

AUDIENCE

Programmers

We design while we deliver.

Agile teams make a challenging demand of their programmers: every week or two, the team is expected to finish 4–10 customer-centric stories. Every week or two, customers may revise the current plan and introduce entirely new stories, with no advance notice. This regimen starts on the very first week.

For programmers, this means you must be able to implement stories, from scratch, in a single week. Because the plan can change at nearly any time, you can’t set aside several weeks for establishing design infrastructure—that work might be wasted when plans change. You’re expected to focus on delivering customer-valued stories instead.

This sounds like a recipe for disaster. Fortunately, incremental design allows you to build your designs incrementally, in small pieces, as you deliver stories.

Never Stop Designing

Computers don’t care what your code looks like. If the code compiles and runs, the computer is happy. Design is for humans: specifically, to allow programmers to easily understand and change the code. Code is well-designed when the costs of change are low.

The secret behind successful Delivering zone teams, therefore, is that they never stop designing. As Ron Jeffries used to say about Extreme Programming, design is so important, we do it all the time. With pairing or mobbing, at least half the programmers on your team are dedicated to thinking about design, and test-driven development encourages you to ...