Unresolved externals when compiling unit tests for Visual C++ 2012

Question

I want to create unit tests for a Visual C++ project. I tried following these MSDN instructions. I've found pages where they differentiate between unmanaged/mixed/pure code, but I don't fully understand those concepts. My code doesn't use .NET and would likely compile under MinGW with a few code adjustments.

My main project builds an executable, so I followed the steps under To reference exported functions from the test project. For starters I got different project options:

I went with Native Unit Test Project. I added a reference to my main project and I set Include Directories to $(SolutionDir)\Cubes;$(IncludePath). I wrote my code and got this when compiling:

1>Creating library C:\Users\Pieter\Dropbox\Unief\TTUI\TTUIproject\Cubes\Debug\CubesTest.lib and object C:\Users\Pieter\Dropbox\Unief\TTUI\TTUIproject\Cubes\Debug\CubesTest.exp
1>LayoutTest.obj : error LNK2019: unresolved external symbol "public: __thiscall Room::Room(void)" (??0Room@@QAE@XZ) referenced in function "public: void __thiscall CubesTest::LayoutTest::NumOfRoomsConsistency(void)" (?NumOfRoomsConsistency@LayoutTest@CubesTest@@QAEXXZ)
1>LayoutTest.obj : error LNK2019: unresolved external symbol "public: __thiscall Layout::Layout(class Room *,int)" (??0Layout@@QAE@PAVRoom@@H@Z) referenced in function "public: void __thiscall CubesTest::LayoutTest::NumOfRoomsConsistency(void)" (?NumOfRoomsConsistency@LayoutTest@CubesTest@@QAEXXZ)
1>LayoutTest.obj : error LNK2019: unresolved external symbol "public: void __thiscall Layout::add(int,int,class Room *)" (?add@Layout@@QAEXHHPAVRoom@@@Z) referenced in function "public: void __thiscall CubesTest::LayoutTest::NumOfRoomsConsistency(void)" (?NumOfRoomsConsistency@LayoutTest@CubesTest@@QAEXXZ)
1>LayoutTest.obj : error LNK2019: unresolved external symbol "public: void __thiscall Layout::clear(int,int,bool)" (?clear@Layout@@QAEXHH_N@Z) referenced in function __catch$?NumOfRoomsConsistency@LayoutTest@CubesTest@@QAEXXZ$0
1>C:\Users\Pieter\Dropbox\Unief\TTUI\TTUIproject\Cubes\Debug\CubesTest.dll : fatal error LNK1120: 4 unresolved externals

If I'm not mistaken, this means that the compiler finds the header files, but not the source files. What am I missing?

Answer 1

Here is a step-by-step description on how to add an EXE as an unit-test target.

The key point is to "export" the functions/classes you want to test... You can download the complete sample here: http://blog.kalmbachnet.de/files/CPP_UnitTestApp.zip (I did not change any project settings, so all changes you can see in the source-code; of course, some parts can be made in the project settings).

1. Create a Win32 Application (Console or MFC or Windows, does not matter); I created a console project called CPP_UnitTestApp:

2. Add a function you want to test (you can also add classes). For example:

   int Plus1(int i)
   {
     return i+1;
   }
   

3. Add a header file for the functions you want to test: CPP_UnitTestApp.h

4. Put the declaration of the methods into the header file, and also export these functions!

   #pragma once
   
   #ifdef EXPORT_TEST_FUNCTIONS
   
   #define MY_CPP_UNITTESTAPP_EXPORT __declspec(dllexport)
   #else
   #define MY_CPP_UNITTESTAPP_EXPORT
   #endif
   
   MY_CPP_UNITTESTAPP_EXPORT int Plus1(int i);
   

5. Include this header file in the main-cpp (here CPP_UnitTestApp.cpp) and define the EXPORT_TEST_FUNCTIONS before including the header:

   #define EXPORT_TEST_FUNCTIONS
   #include "CPP_UnitTestApp.h"
   

6. Now add a new project (Native unit test project: UnitTest1)

7. Include the header and the lib to the "unittest1.cpp" file (adopt the paths as you want):

   #include "..\CPP_UnitTestApp.h"
   #pragma comment(lib, "../Debug/CPP_UnitTestApp.lib")
   

8. Go to the project settings of the test project add add a reference to the "UnitTest1" project (Project|Properties|Common Properties|Add New Reference...: Select under "Projects" the "CPP_UnitTestApp"-Project)

9. Create the unit test function:

   TEST_METHOD(TestMethod1)
   {
     int res = Plus1(12);
     Assert::AreEqual(13, res);
   }
   

10. Run your unit test ;)

As you can see, the main point was to export the function declaration! This is done via __declspec(dllexport) even if it is an EXE.

As I said, the demo project can be downloaded here: http://blog.kalmbachnet.de/files/CPP_UnitTestApp.zip