I’ve been practicing TDD for 6 years and this is exactly what I ended up doing. It’s a fantastic way to program. My leaves are either pure functions (FP langua

I’ve been practicing TDD for 6 years and this is exactly what I ended up doing. It’s a fantastic way to program. My leaves are either pure functions (FP languages) or value objects that init themselves based on other value objects (OOP languages). These value objects have no methods, no computed properties, etc. Just inert data. No mocks and no “header” interfaces needed. On top of that I sprinkle a bunch of UI tests to verify it’s all properly wired up. Works great!