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Posted 30 Jul 2014


, 30 Jul 2014
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This post is an introduction to a library I have written, UnitC++.

This post is an introduction to a library I have written, UnitC++.

UnitC++ is a modern, light weight, header-only C++ library for making unit testing easy. The intention of this library is to make it really easy to test C++ code in a portable way.

How to Use UnitC++

How to Get UnitC++

UnitC++ is stored in a mercurial repository. The best way to get it is to clone it onto local disk. Like so.

cd ~
hg clone

You can also download/clone it from GitHub at

How to Include UnitC++ in Your Project

As a header-only library, this step should be easy to accomplish. However, while how you do this will vary depending on your build process, it will be straightforward. As this is a header-only library, all you need to do is add the repository path to the compiler include line. Here are two examples of how that is done.

From Command Line

Compiling from the command line, you add the argument -I $(path_to_unitc++). This works for g++/clang/cl from the command line. This can also be added to the compiler arguments in a makefile.

From Visual Studio

In Visual Studio, you go to Project Properties -> C/C++ -> Additional Include Directories, and browse to $(path_to_unitc++).

How to Write a Unit Test Using UnitC++

Writing a Test

The first thing to do is include. This is the header which will bring in everything you need.

Then you need to declare you are writing a test by writing TEST(goup_name, test_name). This works like declaring a function, so a set of tests for a class called MyString will look something like this.

#include <UnitCpp/Test.h>

TEST(MyString, length_test)

TEST(MyString, validity_test)

Note: The pattern here is to write several tests for a class with the class as the group_name and what you are testing as the test_name in the TEST macro.

Now you are ready to write the test code. UnitC++ provided some helpful macros for writing tests. Here is a list of them.


So here is a filled out version of the above example of a test.

#include <UnitCpp/Test.h>

TEST(MyString, length_test)
  MyString str("This is a string");
  TEST_EQUAL(str.length(), 16);
  TEST_NOT_EQUAL(str.length(), 17);
  TEST_LESS_THAN(str.length(), 20);
  TEST_MORE_THAN(str.length(), 10);
  TEST_APPROX_EQUAL(str.length(), 15, 1.1); // test the length is within 1.1 of 15

TEST(MyString, validity_test)
  MyString invalid_string;

  MyString valid_string("");

  TEST_THROWS([&](){invalid_string.length();}, MyString::InvalidStringException);

This is obviously a contrived example, there are several tests checking the same thing, i.e., that the length of "This is a string" is 16. However, it is an example of how the macros are used.

Note the use of TEST_THROWS, it is for testing that a certain exception was thrown. It takes a function to call, the exception which should be thrown and the arguments to the function. Note the use of a lambda function, this is because TEST_THROWS is expecting a function and you want to call a member function.

In each TEST, you can use functions from TestCase. This means for example, you can call test_equal(1, some_function()) if you want the values to be compared as doubless not ints.

Running the Tests

So you’ve written a nice set of tests and now you want to run them. This is done with the TestRegister class. This is a singleton that has registered all of the tests you’ve declared with the TEST macro. These are run in the following way:

#include <UnitCpp/TestRegister.h>

int main()
  return UnitCpp::TestRegister::test_register().run_tests();

As long as the code with the tests in is linked into the executable, TestRegister::test_register().run_tests() will run the tests.

You can also call TestRegister::test_register().run_tests("group_name") to run all the tests in a specific group.

Working Examples

In the Example folder, there is a working example for a further demonstration of some of the capabilities of UnitC++.

Frequently Asked Questions

UnitC++ Doesn’t Work With My Compiler!

Ok, this isn’t actually a commonly asked question. But, if your compiler doesn’t work with UnitC++, please let me know! I will fix this as soon as I can. See _How do I report an issue or request a feature_ for how to let me know, thanks.

How Do I Request a Feature or Report an Issue

I am always happy to take a look at an improvement or fix a bug, you just have to let me know about it. The best way to do this is file an issue on my issue tracker. This is located here don’t be shy, I’m not going to snap at anyone.

Do You Use This?

I made UnitC++ for my personal use. This means that I use it whenever I need to test anything.

How is UnitC++ Tested?

It’s tested using UnitC++ of course! I run continuous integration using I currently test it with g++, clang and cl. On, I test g++ and clang and I test/develop with g++ and cl on my windows machine using cygwin. The current state of the build is Build Status.

How Does It Work?

Each TEST does 3 things:

  1. It defines a class derived from TestCase.
  2. It makes a global instance of this class.
  3. It lets you provide the body of the overriden function run().

The reason a global object is declared is to call the constructor. In the constructor of TestCase, it registers itself so TestRegister knows which tests to run. This is how as long as the objects are linked against, TestRegister::test_register().run_tests() will run them all.

You Say This is a Modern Library, Why Are There So Many Preprocessor Macros?

This is because unfortunately macros are the best way of doing some things. Macros are used for 2 reasons in UnitC++.

  1. For judging compiler support. For the TEST_THROWS functionality, we use variadic templates, this was not supported by Visual Studio until 2013. As pre-2013 Visual Studio compilers are in very widely use, we decided to include this functionality for those with compiler support, and to not break the build of those without.
  2. For generating good error messages in tests. Compare the following message; Fail: These arguments should be equal and Fail: "Maths::sqrt(4.0) should equal 2." utest_Maths.cpp:8. I know I prefer the second one, and getting the line of code, file name and line number cannot be done without macros.

Contributing to UnitC++

The GitHub site is a mirror of the mercurial repository. So you should use mercurial and bitbucket. Send me a pull request at and I’ll get back to you.


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

David Corne
Software Developer
United Kingdom United Kingdom
I am a C++ developer with a strong interest in Python, C#, and Qt. I work on a native C++ application which uses COM to call C# in order to use a WPF GUI.

While I develop an application using WPF exclusivly for windows, I am a big linux user. My favourite distro at the moment is Linux Mint, and I love the delights of the command line,.

If you've read something of mine and you enjoyed it, check out my blog.

I am also active on various other sites, listed below.

Coding Sites

  • BitBucket where I keep the majority of my projects.

  • GitHub where I have a few older projects. This includes my current long term project, I'm writing a book about design patterns in python. Find the repository here and blog posts about individual patterns here

  • Stackoverflow I'm not too active on stackoverflow, I'm more of a listener.

  • coderwall and coderbits two profile compilation websites.

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