How to link a file properly in Visual Studio to run native tests?

Question

I'm trying to write unit tests for my classes but I'm getting "unresolved external symbol." There are no syntax errors and I have tried looking up the cause on the official Microsoft website but unfortunately it can be caused for a million different reasons. Any suggestions on what I can do or what might be causing it? This is my code:

// Example.h file
#pragma once
#include <iostream>

using namespace std;

class Example {
public:
  int addTwoNumbers(int first, int second);
};

// Example.cpp file
#include "Example.h"
#include <iostream>

using namespace std;

int Example::addTwoNumbers(int first, int second) {
  return first + second;
}

// Test.cpp file
#include "pch.h"
#include "../Project/Example.h"
#include "CppUnitTest.h"

using namespace Microsoft::VisualStudio::CppUnitTestFramework;

namespace Tests
{
  TEST_CLASS(Tests)
  {
  public:
    TEST_METHOD(UnitTest1)
    {
      Example e;
      Assert::AreEqual(4, e.addTwoNumbers(2, 2)); // this line is causing issues
    }
  };
}

The exact error that I'm getting:

Severity    Code    Description Project File    Line    Suppression State
Error   LNK2019 unresolved external symbol "public: int __thiscall Example::addTwoNumbers(int,int)" (?addTwoNumbers@Example@@QAEHHH@Z) referenced in function "public: void __thiscall Tests::Tests::UnitTest1(void)" (?UnitTest1@Tests@1@QAEXXZ)   Tests   C:\Users\me\source\repos\Tests\Tests.obj    1

In your Test project how are you compiling `Example.cpp`? Or is Example.cpp in a static library? Or have you included Example.obj in your linker setting for the Test project? — drescherjm, Nov 06 '20 at 20:44
Please provide the full error with the symbol that is unresolved. Things to check: if program and test are separate projects, ensure the link tab contains the program/library in the list. Same static or dynamic C++. — un-CharlieH, Nov 06 '20 at 20:55
@drescherjm I have added the Project as a reference by clicking on Tests and then on Add Reference... Is there anything else that I need to do? I have also updates the post with the full error that I'm getting. Thank you! — Kau, Nov 06 '20 at 22:16
@un-CharlieH I have updated the code with the original error. The project and test are different projects but I have added a reference to project in test. How do i check if there are both static or dynamic? Thank you! — Kau, Nov 06 '20 at 22:18
I am not sure references help in native c++ that is more of a .NET / CLR concept, Related: [https://stackoverflow.com/questions/40481799/adding-reference-to-native-visual-c-project](https://stackoverflow.com/questions/40481799/adding-reference-to-native-visual-c-project) — drescherjm, Nov 06 '20 at 22:19
So what would be an alternative? Is there an easier way to unit test? — Kau, Nov 06 '20 at 22:22
The easiest would be to add Example.cpp to your test project by right clicking on the project in Solution Manager and select Add ->existing item — drescherjm, Nov 06 '20 at 22:25
Let us [continue this discussion in chat](https://chat.stackoverflow.com/rooms/224223/discussion-between-drescherjm-and-kau). — drescherjm, Nov 06 '20 at 22:33
@kau: You need to add an import for the test project and export for the Example class in the library. See the [import-and-exporting](https://learn.microsoft.com/en-us/cpp/build/importing-and-exporting?view=msvc-160) topic or the [dllexport SO post](https://stackoverflow.com/questions/48977138/using-declspec-dllexport). — un-CharlieH, Nov 09 '20 at 17:47

Barrnet Chou · Answer 1 · 2020-11-09T08:05:14.210

You could check if the following steps are included. You could refer to this link about Write unit tests for C/C++ in Visual Studio.

Add Reference to UnitTest.
Link to object or library files: Properties->Linker->Input->Additional Dependencies->input ..\ProjectName\Debug\*.obj
Add #include directives for header files: #include "../Project1/Example.h"

If the lnk2019 still appears, try to add the following code to Example.cpp.

#include<iostream>
#include "Example.h"
using namespace std;

int Example::addTwoNumbers(int first, int second) {
    return first + second;
}

int main()
{
    return 0;
}

How to link a file properly in Visual Studio to run native tests?

1 Answers1