I’ve written a chapter in my book on The Relationship Between ATDD and Design Patterns. Essentially, ATDD provides us with quality acceptance criteria in the form of test specifications. We can use these to design our code from a behavior point of view instead of from an implementation point of view.
Doing this makes for more testable code, a quality highly correlated with other code qualities we want – strong cohesion, loose coupling and no redundancy. Design patters provide us with a method for combining these high quality objects together through the Gang of Four’s mantra’s of designing to behavior, using variation and encapsulating variation – in this case variation of type.
In the Agile world where requirements evolve, ATDD and Design Patterns Thinking work together to enable emerging designs from emerging requirements.