Comment by lukeramsden

Part of test-driven design is using the tests to drive out a sensible and easy to use interface for the system under test, and to make it testable from the get-go (not too much non-determinism, threading issues, whatever it is). It's well known that you should likely _delete these tests_ once you've written higher level ones that are more testing behaviour than implementation! But the best and quickest way to get to having high quality _behaviour_ tests is to start by using "implementation tests" to make sure you have an easily testable system, and then go from there.