Hm, yes and no. I do feel that mockist TDD is still heavily emphasising the OOP idea (more in the original sense than in the Java sense) of having separate "col

Hm, yes and no. I do feel that mockist TDD is still heavily emphasising the OOP idea (more in the original sense than in the Java sense) of having separate "collaborators" with their own internal state and side effects that exchange messages (in a way similar to the Actor pattern). A functional approach (at least in a pure functional language) wouldn't necessarily emphasise this sort of interaction pattern between independent components and try to isolate state and side effects much more.