Discover the Domain

In this part we used the specifications to discover the domain of the underlying system. Initially, we had a vague idea of the underlying structure for the production code. While automating one example after another, we validated our thoughts. When we had a clear idea about how the production design might look, we started to write the production class for the domain code.

The implementation of the glue code helped to discover the domain. Once we could spot an implementation that supported the examples identified thus far, we could reflect on the code and try to find patterns that motivate the code for the domain. Once we could see the domain behavior growing in the glue code, the step toward either extracting the domain code from the glue code or writing it in parallel in a new class became obvious.