Saturday, November 27, 2004

Friendy C++ Unit Tests In C++ the friend keyword makes writing unit test code easy and clean. The question is how do you keep your test code separate from your "real" code while having a minimal public interface and allowing seperate test classes access to the internals of the classes being tested? I want code separation so my code is clean and the final image doesn't include test code. As the test code is usually larger than the code being tested this is important. Please, no separate compilation using macros. I believe in testing everything that can break so i don't just test public interfaces. Public interfaces often use a common private interface that i want to be able to test directly so it doesn't have to be retested for each public interface. This requires another class to have non-public access to the innards of another class. In C++ this is what friend does for you, rather cleanly. Test classes can be put in another package. And with a forward declaration and the friend keyword, a class can be put under test by any number of other test classes. class TestClass; class ClassTested { private: friend TestClass; }; The implementation source file would include the path to the full TestClass. I allow all the code in a package to touch the privates of other classes in the same package. This makes for a minimum public display of behaviour. I assume all code in the same package goes together somehow so there's no need for a class to protect itself from code in the same package. comment[] 1:40:25 PM

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