The difference between expect my_func to call thing.method and expect my_func to return a call_thing_method Might not seem like much except that the impleme

The difference between expect my_func to call thing.method and expect my_func to return a call_thing_method Might not seem like much except that the implementation of indirection is one that is in place during production and whole-system tests - a genuine article - and not one that is only in place during unit testing. An indirection that behaves contrary to how it's expected to but is used in production or whole-system testing can be found, a faulty indirection that exists only during a particular unit test goes unnoticed