One of the points being discussed here is the impact on velocity due to tests not being functional and tests validating implementation details. This slows down

One of the points being discussed here is the impact on velocity due to tests not being functional and tests validating implementation details. This slows down refactoring or re-design exercises, which is quite inevitable in any customer driven project. I suggest looking at BDD (http://guide.agilealliance.org/guide/bdd.html http://guide.agilealliance.org/guide/bdd.html) which results in tests that validate scenarios/specification/behavior and are not coupled too closely with the implementation details.