Skill Trumps Testing
We are working on a complex app and we are not sure exactly what the use case is yet, but we want to use programmatic design to flesh it out by iterating on it rapidly until we feel like our mental model of the use case and the corresponding implementation feels right.
Iterate on a simple design and example of the use case without writing tests.
Once the design is solid enough and we have a good feel for it, lock down the edge cases of the design with unit and integration tests.
Now the design is ready and can be used as a component or integration piece in a larger picture.