Google Test: error LNK2019: unresolved external symbol with Visual Studio 2013

Question

I'm trying to get my first ever unit test with Google Test framework + Visual Studio 2013.However I'm hitting the below error and can't understand why.

1>------ Build started: Project: FirstGoogleTest, Configuration: Debug Win32 ------
2>------ Build started: Project: googleTest, Configuration: Debug Win32 ------
1> MyMultiplier.cpp
2> gtest_main.cc
1> main.cpp
1> Generating Code...
2> gtest-all.cc
1> FirstGoogleTest.vcxproj -> D:_Vault\Workspaces\UnitTestLearning\FirstGoogleTest\Debug\FirstGoogleTest.exe
2> Generating Code...
2> googleTest.vcxproj -> D:_Vault\Workspaces\UnitTestLearning\FirstGoogleTest\Debug\googleTest.lib
3>------ Build started: Project: MyMultiplier_UnitLevelTest, Configuration: Debug Win32 ------
3> MyMultiplier_UnitLevelTest.cpp
3>MyMultiplier_UnitLevelTest.obj : error LNK2019: unresolved external symbol "public: unsigned int __thiscall
MyMultiplier::multiply(unsigned int,unsigned int)" (?multiply@MyMultiplier@@QAEIII@Z) referenced in function "private: virtual void __thiscall MyMultiplier_multiplyNormalSmallValues_Test::TestBody(void)" (?TestBody@MyMultiplier_multiplyNormalSmallValues_Test@@EAEXXZ)
3>D:_Vault\Workspaces\UnitTestLearning\FirstGoogleTest\Debug\MyMultiplier_UnitLevelTest.exe : fatal error LNK1120: 1 unresolved externals
========== Build: 2 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

The solution structures is as follow:
https://www.dropbox.com/s/0cu8eqr7pz3ajaz/Untitled.png

The ULT project's "References" projects include "googleTest" and "FirstGoogleTest". here is the "MyMultiplier_UnitLevelTest.cpp"

#include "gtest/gtest.h"  // access test macro
#include "MyMultiplier.h"   // testee
#include <iostream>
#include <string>

TEST(MyMultiplier, multiplyNormalSmallValues){
    MyMultiplier m;
    std::string name("MyMultiplier_ULT");
    unsigned int a = 5;
    unsigned int b = 10;
    unsigned int answer = m.multiply(a, b/*, name*/);
    ASSERT_EQ(a * b, answer);

}

the "multiply" function's declaration in MyMultiplier.h:

class MyMultiplier{
public:
    unsigned int multiply(unsigned int a, unsigned int b/*, std::string& name*/);
};

the signature matches and also the header file is included. why the ult project can't find the symbol?

the entire solution can be downloaded here: https://www.dropbox.com/sh/vc89o5ep139wkuk/AAA8Z76q6iAkP25zTmu9bR3ia

Solution 1

The root cause is the project type is not set correctly.

In this example, there are three projects:

1. FirstGoogleTest, which is the testee. the class to be tested resides in here.
   
2. googleTest, which is the google test framework
   
3. MyMultiplier_UnitLevelTest, which is the ULT project that contains the tests.
   

The root cause is "FirstGoogleTest" project's configuration Type was set to .exe, which is the same as the ULT project. so the ult test cannot get the externals from "FirstGoogleTest". After changing "FirstGoogleTest" configuration Type to Static library (.lib). the solution can be compiled correctly and the ULT runs fine.

Solution 2

The issue here is that you didn't include MyMultiplier.h/cpp in the actual test project.

Add it to the project file (right-click, add existing item and navigate to the files).

Solution 3

I solved a similar problem by including the cpp files (I created a Visual Studio Project for testing with GoogleTest my own class "Number" (.h + .cpp))

Didn't work:

#include "pch.h"
#include "..\..\LAB2\Number.h"

class TestLab2 : public ::testing::Test {
public:
    TestLab2() {
        Number n;
    }
}

Worked:

#include "pch.h"
#include "..\..\LAB2\Number.h"
#include "..\..\LAB2\Number.cpp"

class TestLab2 : public ::testing::Test {
public:
    TestLab2() {
        Number n;
    }
}

Comments

[Solti]

in this case, what would be the missing lib file? the error is referring to multiply function inside MyMultiplier. but MyMultiplier is not a lib file...

[KnightsValour]

How are the functions in FirstGoogleTest and googleTest exported for your use in MyMultiplier_UnitLevelTest? Perhaps I've misunderstood your comment response - but I assumed that you were using .dlls and had already generated .lib files.

[Solti]

I followed a Google Test tutorial video, in which the ULT project only need to do (1) add FirstGoogleTest and GoogleTest as "Reference" projects to the ULT project (2) add the directory paths of FirstGoogleTest and Google test to ULT project's "Include Directories" property<br> in the tutorial video, it works totally fine but not on my case.

[Solti]

It turns out your direction is right. it's about the library linking stuff. I need to change the testee project type to static library to resolve the issue.

[KnightsValour]

Ah I see - didn't realize it could all be done in one step. Glad that it's working for you.

[kinar]

This is not a good solution. It requires everything you test to be a library. What if you are testing an executable? Are you going to maintain a second set of project files to build everything into libraries just for unit testing?