Using FRIEND_TEST to test private functions of a class in another namespace-CodePudding

I'm trying to use GTest's FRIEND_TEST() macro to enable testing of some private functions from another namespace. However, I can't get past some errors, though I must be missing something simple.

I have Tests.cpp where I would like to test private functionality of MyClass:

namespace a::b::tests 
{

  class MyTests : public ::testing::Test { ... };

  TEST_F(MyTests, Test1)
  {
    // Test private functions of MyClass instance from MyClass.cpp
    ...
  }

}

In MyClass.h, implemented in MyClass.cpp, I have:

namespace a::b
{
  class MyTests_Test1_Test; // Forward declaration.

  class MyClass
  {
    private:
      FRIEND_TEST(a::b::tests::MyTests, Test1);   
      ...
  };
}

However, this fails with compile-time errors 'a::b::tests' has not been declared and error: friend declaration does not name a class or function.

If I try to forward-declare the namespace by adding using a::b::tests; in MyClass.h, the error remains.

How can I properly make MyTests a friend class of MyClass here?

CodePudding user response：

You need to add a forward declaration for a::b::tests::MyTests because you've implemented it in a source file Tests.cpp which is different from the header file MyClass.h and at the point where you've written FRIEND_TEST(a::b::tests::MyTests, Test1); the compiler doesn't know that there is a class a::b::tests::MyTests.

So to solve this add this in your header file MyClass.h:

MyClass.h

namespace a::b::tests 
{
//-------------v-------------->note only a declaration and not a definition
  class MyTests;//added this forward declaration
}
////////////////////////////
//now we can write the below code exactly as before since we have a forward declaration for a::b::tests::MyTests

namespace a::b
{
  class MyTests_Test1_Test; 

  class MyClass
  {
    private:
      FRIEND_TEST(a::b::tests::MyTests, Test1);   
      ...
  };
}

CodePudding user response：

Turns out I had to do forward declarations like this, in MyClass.h:

namespace a::b::tests
{
    class MyTests;
    class MyTests_Test1_Test;
}

namespace a::b 
{
  class MyClass
  {
    private:
      FRIEND_TEST(a::b::tests::MyTests, Test1);   
      ...
  };
}