Josh Reuben

C++ Unit Testing with GoogleTest

Unit testing is critical for quality code – they help you:

• find problems early
• facilitate change by avoiding breakage of other functionality
• simplify integration via a bottom up approach
• document the code
• maintain good design – testable code is good code: single intent, clear retval etc

Google has created a unit testing framework for C++ :

http://code.google.com/p/googletest/

I downloaded Google Test from http://code.google.com/p/googletest/downloads/list and built the solution under the msvc folder (Im using Visual C++ today). I see that there is a lib file created here called gtest-1.6.0\msvc\gtest\Debug\gtestd.lib

I then created a new VC++ Win32 Console App and set the following project properties:

VC++ Directories > Include Directories – added path to ..\ gtest-1.6.0\include

VC++ Directories > Library Directories – added path to ..\ gtest-1.6.0\msvc\gtest\Debug

Linker > Input > Additional Dependencies  - added gtestd.lib

All swell ?

I thought so, until I compiled & got the dreaded LNK2005: http://msdn.microsoft.com/en-us/library/72zdcz6f(v=vs.80).aspx

WTF – linker errors ?

To quote Cousin Eddie from National Lampoon’s Vacation:

'Everytime Catherine would turn in the microwave I'd piss my pants and forget my name' - C++ often makes me feel like an idiot !

Thank God for Pavel http://blogs.microsoft.co.il/blogs/pavely/ , who pointed out to me that I need to change the C runtime library from DLL multithreaded debug to multithreaded debug:

I could now build.

I added an include to access the Google Test macros:

#include "gtest/gtest.h"

I then created a canonical testable function:

int Factorial(int x, int result = 1) {

if (x == 1) return result;

else return Factorial(x - 1, x * result);

}

I used the TEST macro to construct a named test – it leveraged the EXPECT_EQ & EXPECT_GT macros to test for equality and greater than respectably.

TEST(FactorialTest, Negative) {

        EXPECT_EQ(1, Factorial(-1));

        EXPECT_GT(Factorial(-10), 0);

}

in my main function, I initialized google test & used RUN_ALL_TESTS macro to … run all tests.

int _tmain(int argc, _TCHAR* argv[])

{

        testing::InitGoogleTest(&argc,argv);

        RUN_ALL_TESTS();

        int x;  

        std::cin >> x;

        return 0;

}

I debugged my code - It breaks into the test:

And I get the following test results displayed:

So I am up & running with C++ Google Test !

Further things to try:

• Visual Studio Addin: http://googletestaddin.codeplex.com/ 
• TypeMock Isolator mocking framework: http://www.typemock.com/isolatorpp-product-page

All fun & games !

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Print | posted on Monday, January 28, 2013 12:24 PM

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