Growing Object-Oriented Software, Guided by tests

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Problem domain vs solution domain.

Video game example. Problem: actors, scene, effects… Solution: renderer, animator, collision detector…

An object is an implementation of one or more roles; a role is a set of related responsibilities; a responsibility is an obligation to perform a task or know information.

CRC cards: candidate, responsibilities, collaborators

…nothing forces us to understand a process better than trying to automate it.

1. Understand the problem
2. Broad-brush design
3. Automate: build, deployment, end-to-end test
4. ATDD-TDD cycle

Walking skeleton.