At Wealthfront we are on a 5-minute commit-to-production cycle and have adopted continuous deployment as the natural next step to CI. This talk will cover how we achieved the core of our extreme iteration cycles: TDD. We will look at two fundamental aspects of software: stateless data operations (transformations) and dealing with state (interactions). With this background we will delve into practical matters, surveying various testing approaches which will be thoroughly motivated.

Conversations surrounding TDD tend to be riddled with statements along the lines of “Tests are really <something else>.” While I am certainly not going to try and convince you that “tests aren’t really tests,” we will briefly discuss how tests can be used for process control, specification, analysis, design, etc. In fact, I believe the list of duties that a test can fulfill will continue to grow for decades.

The point of this talk is to open up our eyes to yet another way to look at tests and reconciling them with lean principles. Tests are also increments of process improvement.