I think what he wants is to have automatically generated unittests for
derived classes that check if the unittests of the parent still pass for
them. I don't know of a nice way to do that without requiring some
minimal effort by the implementor of the derived class. Contracts
quickly detect and report otherwise potentially unnoticed bugs during
test runs, but they don't provide the robustness of running actual unit
tests. The two features can be combined very well though.
Yes, that's it.
Actually, I'm not blaming D, as I explained, the same problem exists
with others languages.
Contract is a part of the solution, but not really the same as unittest.
Indeed, contract are very compatible with Liskov's principle, but
unittest isn't.
I just wanted to open up the discution on that.
