Agreed. In general, I prefer integration tests, especially end to end tests. The one exception is for utility functions. I advocate TDD for utility functions,

Agreed. In general, I prefer integration tests, especially end to end tests. The one exception is for utility functions. I advocate TDD for utility functions, with heavy testing of standard and edge cases, to ensure that the functions conform to spec and any future tweaks / refactors of the functions continue to conform to spec.