Unit testing handling of degraded network stack, file corruption, and other imperfections

Question

I\'m primarily a C++ coder, and thus far, have managed without really writing tests for all of my code. I\'ve decided this is a Bad Idea(tm), after adding new features that subt

Answer 1

The beauty of mock objects is that you can have more than one. Assume that you are programming against a well-defined interface for a network stack. Then you can have a mock object WellBehavingNetworkStack to test the normal case and another mock object OddlyBehavingNetworkStack that simulates some of the network failures that you expect.

Using unit tests I usually also test argument validation (like ensuring that my code throws NullPointerExceptions), and this is easy in Java, but difficult in C++, since in the latter language you can hit undefined behavior quite easily, and then all bets are off. Therefore you cannot be strictly sure that your unit tests work, even if they seem to. But still you can test for odd situations that do not invoke undefined behavior, which should be quite a lot in well-written code.