CMake and CppUTest

Posted by R4nd0m 6uy on Tue 21 February 2017

When implementing a new feature or fixing bugs, I like having a quick feedback to make sure that my changes didn't break the code. This is why I usually write unit tests and execute them during the build process. In this article I want to give some pointers to make my favorite tools work well together that are the CppUtest unit testing framework and the cmake build utility.

I like cmake because it creates excellent Makefiles that is usually difficult to get right. As a developper, it compiles only files that changed that is very efficient when your recompiling your tests very frequently. cmake is supported by many build systems that facilitates the deployement on embedded targets and can be easily added to your contineous integration process where you want to compile the unit tests automatically.

There are many out the but CppUTest is a well proven unit test framework. I like it because it has a mocking framework, a memory leak detector and doesn't need other external libraries to compile.

Installing cmake and CppUTest

Those tools should be available in your distribution, you should use your package manager to install them. As long as it is decent enough, I don't mind much about cmake version but I like working with the last development version of CppUTest and maybe want to use different version when compiling a stable release.

There are different ways to compile CppUTest but as long as we are talking about cmake, I will use this way. The default installation path is /usr/local but as I want to host different version, I define the prefix to /opt/cpputest-:

git clone ; cd cpputest
mkdir cmake-build ; cd cmake-build
cmake ../ -DCMAKE_INSTALL_PREFIX:PATH=/opt/cpputest-$(git describe)
make -j3

Once the compilation is done, you can run make install and make an user friendly symbolic link to the last available version:

sudo make install
sudo ln -s /opt/cpputest-$(git describe) /opt/cpputest

To switch from a version to another, I just change the /opt/cpputest symlink.

The project structure

My favorite structure is having the sources and tests in separated folders. I write a root CMakeLists.txt that can include what I want to compile, it should be easy to build the application without the tests. Here is a skeleton showing what your project would look like:

├── CMakeLists.txt
├── src
│   ├── CMakeLists.txt
│   ├── main.cpp
│   └── time
│       ├── Bar.cpp
│       ├── Bar.hpp
│       ├── Foo.cpp
│       ├── Foo.hpp
│       ├── IFoo.cpp
│       └── IFoo.hpp
└── tests
    ├── CMakeLists.txt
    ├── BarTest.cpp
    ├── FooTest.cpp
    ├── main.cpp
    └── mocks
        ├── IFooMock.cpp
        └── IFooMOck.hpp


Now the intersting part is writing CMakeFiles. Here is what looks like the root CMakeLists.txt:

# (1) CMake definitions, compiler flags and useful variables
cmake_minimum_required(VERSION 3.7)

add_compile_options(-std=c++11 -Wall -Werror)

set(APP_NAME fooApp)
set(APP_LIB_NAME fooAppLib)

# (2) Include application build instructions

# (3) include tests build instructions   
option(COMPILE_TESTS "Compile the tests" OFF)


First the usual cmake options, we need to define a project name and decide which version of cmake we need. I also add some restrictive compiliation flags and declare some variables that I can share between both subprojects, the application and the tests.


Because making sure that the application compiles is an excellent test, this is done all the time and include the sub cmakefile.


Compiling the unit tests is probably not a required step for everyone, this is why I want to give explicitely the option to do it by passing COMPILE_TESTS=ON to cmake.


Here is how looks the instruction to build the main application:

# (1) Build a library with my application sources

add_library(${APP_LIB_NAME} ${APP_LIB_SOURCE})

# (2) Add main(..) to the application library to have something we can run
add_executable(${APP_NAME} main.cpp)
target_link_libraries(${APP_NAME} ${APP_LIB_NAME})


The trick is to use a separated main function from the application sources, so it doesn't conflict with the main from the tests. We simply compile here a static library that can be used when linking with the tests or the main from the normal program.


As we have all the objects we need, we add the main file where we can provide an entry point.


Finally, how to build the unit tests that you wrote using CppUtest:

# (1) Look for installed version of CppUTest
    message(STATUS "Using CppUTest home: $ENV{CPPUTEST_HOME}")
    set(CPPUTEST_LDFLAGS CppUTest CppUTestExt)
    find_package(PkgConfig REQUIRED)
    pkg_search_module(CPPUTEST REQUIRED cpputest>=3.8)
    message(STATUS "Found CppUTest version ${CPPUTEST_VERSION}")

# (2) Our unit tests sources
set(TEST_APP_NAME ${APP_NAME}_tests)

# (3) Take care of include directories
include_directories(${CPPUTEST_INCLUDE_DIRS} ../src/)

# (4) Build the unit tests objects and link then with the app library
add_executable(${TEST_APP_NAME} ${TEST_SOURCES})
target_link_libraries(${TEST_APP_NAME} ${APP_LIB_NAME} ${CPPUTEST_LDFLAGS})

# (5) Run the test once the build is done


If the user has CPPUTEST_HOME set in his environment, we use it to locate CppUTest installation. In case it is not provided, we use pkgconfig to look for it in the system. The cmake process fails here if CppUTest is not found or its version is too old.


Then we add all the sources required to compile the unit tests, including the main function.


We have to define the include directory of our application source so the compiler can find our headers files. We also have to take care of CppUTest include directories variables we set previously.


Compile the unit test application by linking it with our library and CppUTest.


Finally run the tests once it is built! If the unit test fails, the make command will also fail, that gives us a quick feedback if everything is fine!

Compile the whole

To compile the application, proceed the usual cmake way:

mkdir build ; cd build
cmake ../
make -j3

If you want to compile the unit tests, execute cmake with this parameter:


If you haven't installed cpputest or use a too old version, this error will pop out:

-- Checking for one of the modules 'cpputest>=3.8'
CMake Error at /usr/share/cmake-3.7/Modules/FindPkgConfig.cmake:637 (message):
  None of the required 'cpputest>=3.8' found
Call Stack (most recent call first):
  tests/CMakeLists.txt:8 (pkg_search_module)

You can install cpputest with your package manager or set the CPPUTEST_HOME environment variables pointing to your last version:

CPPUTEST_HOME=/opt/cpputest/ cmake -DCOMPILE_TESTS=ON ../

Once cmake ran correcly, you just need to run make to (re)build the changes and run the unit tests:

make -j3
[100%] Linking CXX executable fooApp_tests
OK (52 tests, 52 ran, 112 checks, 0 ignored, 0 filtered out, 7 ms)

[100%] Built target fooApp_tests


Now you have a template that you can use it for your own project and be efficient by having a quick feedback if something goes wrong!