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Thibaut Andrieu
Thibaut Andrieu

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Tiny Tips : Testing protected method without using friendship in C++

Assume you have this class to test:


class MyClass {
    float publicMethod();
    float criticalInternalMethod();
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criticalInternalMethod() implement a complex business logic or algorithm, but it is too internal to make it part of public API. How to test it ?

With GoogleTest, you can use the FRIEND_TEST macro. But it requires putting google header in public API, and a macro in class definition.

What you can do instead is this:


class MyClassTest : public MyClass
    using MyClass::criticalInternalMethod;

TEST(MyClassShould, computeGoodResult)
    MyClassTest myClass;
    EXPECT_EQ(myClass.criticalInternalMethod(), 12);
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This doesn't work for private method, but at least it avoids polluting public header only for the sake of testing.

Top comments (1)

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Mujtaba Aldebes

This also dosn't work if MyClass is final, but nice tips.