Unit test a variable for both true and false

问题

I'm working on a C++ production code here with googletest/googlemock. I've stumble upon this idea when working with one of the function in A.cpp:

bool A::process_(false);

bool A::process()
{
    if ( !process_ ){
        process_ = true;
    }
return process_;
}

where the header contains:

protected:
    static bool process_;
public:
    static bool process();

I am stuck in a way that I can only test the function for an expected output of true or an input of false like so:

TEST(ATest, processVal){

    A a;
    EXPECT_TRUE(a.process());

}

Is there a way to test the function so that both *true* and *false* value of process_ is passed ? So that the test covers the decision for both. I was thinking mocking so that it can expect a call for both true and false but because it is not a function in a member of a class, I guess you can not do mocking for process_ ? If you can, how to mock the variable?

Note: I'm on linux and gcc :) thank you !

回答1:

Solution1: To access any protected attribute/method from a test without modifying production code

You can easily modify _process even if protected, just do this:

class SubA : public A
{
public:
    void setProcess( bool val ) { process_ = val; }
};

A a;
SubA* pA = (SubA*) &a;
pA->setProcess( false );

This will work pretty well and is safe. Even if you are casting A* to SubA* which is not really valid, it will work as SubA objects in memory are the same as A objects (as SubA does not declare any extra attribute).

This only works because process_ is protected, so you create a derived class SubA and use it because compiler will allow this subclass to access the protected stuff.

Solution2: To access any protected and even private attribute/method from a test without modifying production code

Now, if process_ was private, this would not work...but, private/protected is only managed by the compiler...the attributes are here in memory and you may access them even if you are not "allowed to".

It's ugly but works perfectly:

#define protected public
#define private public
#include "A.h"
#undef private
#undef protected

{
    A a;
    a._process = false;
}

This hack makes it easy to access any private/protected attributes/functions from your test programs.

回答2:

Declare a subclass of A. Since process_ is protected, you can use the subclass of A to set it totrueorfalse`, before running the test.

来源：https://stackoverflow.com/questions/37346690/unit-test-a-variable-for-both-true-and-false

标签

c++

Linux

unit-testing

googletest