Unresolved external symbol with google test framework - unit-testing

Question

I try to implement google test framework for verifing dll library into my existed solution by visual studio community 2019. Basically, I have 3 files:
Source code is built in single dll project.
FooCmdMgr.cpp
FooCmdMgr.h
Unit test code using the latest google test framework in other project in a same solution with source code.
FooCmdMgr_Test.cpp
FooCmdMgr.h
class FooCmdMgr
{
public:
FooCmdMgr(const FooCmdMgr&) = delete;
FooCmdMgr& operator=(const FooCmdMgr& ) = delete;
bool func_1() {
return true;
}
private:
FooCmdMgr();
~FooCmdMgr();
static FooCmdMgr& Instance ( );
friend FooCmdMgr& GetFooCmdMgr ( );
};
inline FooCmdMgr& GetFooCmdMgr()
{
return FooCmdMgr::Instance();
}
FooCmdMgr_Test.cpp
#include "stdafx.h"
#include "../FooCmdMgr.h"
TEST_F(CJobChangeTestFixture, UnitTest2) {
FooCmdMgr& FooCmdMgr = ICmdEx::FooCmdMgr();
//bool bRet = FooCmdMgr.func_1();
//EXPECT_EQ(bRet, true);
}
Solution was compliled successful but linker was not OK.
It shown error LNK2019 something likes this:
Severity Code Description Project File Line Suppression State
Error LNK2019 unresolved external symbol "private: static class ICmdEx::FooCmdMgr & __cdecl ICmdEx::FooCmdMgr::Instance(void)" (?Instance#FooCmdMgr#ICmdEx##CAAEAV12#XZ) referenced in function "class ICmdEx::FooCmdMgr & __cdecl ICmdEx::GetIKYCmdMgr(void)" (?GetIKYCmdMgr#ICmdEx##YAAEAVFooCmdMgr#1#XZ) IEditorDll_GTest E:\work\project\UnitTest\FooCmdMgr_Test.obj
Project structure
E:\work\project\FooCmdMgr.vcxproj
E:\work\project\FooCmdMgr.cpp
E:\work\project\FooCmdMgr.h
E:\work\project\FooCmdMgr.dll
E:\work\project\FooCmdMgr.lib
Google test project
E:\work\project\UnitTest\FooCmdMgr_Test.vcxproj
E:\work\project\UnitTest\FooCmdMgr_Test.cpp
I also change the configuration of linker in gtest project
General/Additional Library Directories
$(ProjectDir)../
Input/Additional Dependencies/
FooCmdMgr.lib
I am struggling to figure out what happened with linker? Please give me advise.

Answer 1

your Foo class should be like this
#pragma once
#ifdef PROJECT1_EXPORTS
#define PROJECT1_API __declspec(dllexport)
#else
#define PROJECT1_API __declspec(dllimport)
#endif
class PROJECT1_API Foo
{
};
PROJECT1_EXPORTS is defined in your main source PREPROCESSOR project.
and it will NOT be define in your Test project

Answer 2

I had the same problem and fixed it by adding the output .obj/.lib files to the dependencies of the test project as described here: https://learn.microsoft.com/en-us/previous-versions/visualstudio/visual-studio-2015/test/unit-testing-existing-cpp-applications-with-test-explorer?view=vs-2015&redirectedfrom=MSDN#objectRef
I have Visual Studio 2022 with Google Test, and for me, it was enough to perform only steps 2 to 4 from the instruction. I.e.:
In Solution Explorer, on the shortcut menu of the test project, choose Properties. The project properties window opens.
Choose Configuration Properties, Linker, Input, Additional Dependencies.
Choose Edit, and add the names of the .obj or .lib files. Do not use the full path names.
Choose Configuration Properties, Linker, General, Additional Library Directories.
Choose Edit, and add the directory path of the .obj or .lib files. The path is typically within the build folder of the project under test.
I use NVIDIA CUDA, so needed to add its .lib file and path too.