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White box testing - friends or preprocessor?

Imagine we have a class:

class Testee { public: void Func() private: void auxFunc() };

and we want to conduct a block test on it on a white box. What do you think is the best approach? Declare the tester class as a friend of the test class? Or use a preprocessor as follows:

  class Testee { public: void Func() #ifndef UNITTEST_SYMBOL private: #elif public: #endif void auxFunc() };

and then in the test file

 #define UNITTEST_SYMBOL #include "Testee.h" #undef UNITTEST_SYMBOL

So, again, what do you think is the best approach? Or maybe you could suggest a different approach.

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4 answers

What about:

 #ifndef UNITTEST_SYMBOL #define semiprivate private #else #define semiprivate public #endif

and declare your class as follows:

  class Testee  {  public:    void Func()  semiprivate:    void auxFunc()  };

or even if you hold on enough, #define private public when testing

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In the unit test file. You can try

 #define private public #include "Testee.h"

This is what I am doing, it means that there is nothing related to unit testing in the header file. I find this very useful as it is hard for me to follow when there is a lot of #ifdef in my code.

Then I have all my header files before #define

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Using the friend method, the declaration will depend on the name of the test class, so if you ever change its name, the declaration must also be changed. In addition, I use Unittest ++, so the actual name of the test calss is formed by a macro.

Then the method with the definition is less hassle. Also, I would just put the definition as a global compiler option instead of the way you show, e.g.

 gcc -DUNIT_TESTING_ON #ifdef UNIT_TESTING_ON public: //or protected maybe #else private: #endif

Anyone who reads this also sees what the purpose is, it is more clear than looking for a friend’s definition to understand why you made him a friend.

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Below is the way people follow to test the white box,

 #define private friend cTestDriver; private #define protected friend cTestDriver; protected //included all your class header from which you like to access //the private/protected method #include Testee.h" #undef private #undef protected

The cTestDriver class will have shells / setters / getters to access all private and protected members.

You should also be aware of the order of the header files.

For instance:

File1.h

 #include "Testee.h" -- -- --

file TestDriver.h

 #include File1.h #define private friend cTestDriver; private #define protected friend cTestDriver; protected //included all your class header from which you like to access //the private/protected method #include Testee.h" #undef private #undef protected

In the above case, Testee.h will be open while we open File1.h. So macros here will not be effective.

Note: you may receive a warning about multiple friend announcements.

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