What is the best way to unit test a protected method in C++?

Question

What is the best way to unit test a protected method in C++?

In Java, I'd either create the test class in the same package as the class under test or create an anonymous subclass that exposes the method I need in my test class. Because neither of those methods are available to me in C++, what are suggested approaches for testing protected methods in C++ classes?

I am testing an unmanaged C++ class using NUnit.

Answer 1

One approach :

http://praveen.kumar.in/2008/01/02/how-to-unit-test-c-private-and-protected-member-functions/

Answer 2

Consider a public, possibly static 'unit test' function.

Ugly, but better than the alternatives I can think of using macros or friends or such.

Answer 3

Declare a friend class MyClass_UnitTest; in your MyClass. You can then define MyClass_UnitTest elsewhere in your unit test program that has full access to MyClass internals, but you don't have to provide an implementation in your release application. See CppUnit documentation for a good example of how this is done.

Answer 4

Assuming you mean a protected method of a publicly-accessible class:

In the test code, define a derived class of the class under test (either directly, or from one of its derived classes). Add accessors for the protected members, or perform tests within your derived class . "protected" access control really isn't very scary in C++: it requires no co-operation from the base class to "crack into" it. So it's best not to introduce any "test code" into the base class, not even a friend declaration:

// in realclass.h
class RealClass {
    protected:
    int foo(int a) { return a+1; }
};

// in test code
#include "realclass.h"
class Test : public RealClass {
    public:
    int wrapfoo(int a) { return foo(a); }
    void testfoo(int input, int expected) {
        assert(foo(input) == expected);
    }
};

Test blah;
assert(blah.wrapfoo(1) == 2);
blah.testfoo(E_TO_THE_I_PI, 0);

Answer 5

I use CxxTest and have the CxxTest derive from the class that contains the protected member function. If you're still searching around for your favorite C++ Unit Testing framework, take a look at this article.