Myopia And Hyperopia
Assume that we’ve just finished designing, testing, and integrating the system below:
Now let’s zoom in on the “as-built“, four class, design of SS2 (SubSystem 2). Assume its physical source tree is laid out as follows:
Given this design data after the fact, some questions may come to mind: How did the four class design cluster come into being? Did the design emerge first, the production code second, and the unit tests come third in a neat and orderly fashion? Did the tests come first and the design emerge second? Who gives a sh-t what the order and linearity of creation was, and perhaps more importantly, why would someone give a sh-t?
It seems that the TDD community thinks the way a design manifests is of supreme concern. You see, some hard core TDD zealots think that designing and writing the test code first ala a strict “red-green-refactor” personal process guarantees a “better” final design than any other way. And damn it, if you don’t do TDD, you’re a second class citizen.
BD00 thinks that as long as refactoring feedback loops exist between the designing-coding-testing efforts, it really doesn’t freakin’ matter which is the cart and which is the horse, nor even which comes first. TDD starts with a local, myopic view and iteratively moves upward towards global abstraction. DDT (Design Driven Test) starts with a global, hyperopic view and iteratively moves downward towards local implementation. A chaotic, hybrid, myopia-hyperopia approach starts anywhere and jumps back and forth as the developer sees fit. It’s all about the freedom to choose what’s best in the moment for you.
Notice that TDD says nothing about how the purely abstract, higher level, three-subsystem cluster (especially the inter-subsystem interfaces) that comprise the “finished” system should come into being. Perhaps the TDD community can (should?) concoct and mandate a new and hip personal process to cover software system level design?