Testing on the C++ track

Learn how to test your C++ exercises on Exercism

Each exercise supplies the unit tests and a CMake build recipe. You provide the implementation. Each test file is meant to link against your implementation to provide a console executable that runs the tests. Running the test executable prints messages for each failing test and reports a non-zero exit status when tests fail.

Note: Your code is being tested against the test suite every time you build your project. If your code does not pass the one or more tests but is valid C++ code, it will still be compiled.

Working through each exercise is a process of:

  • Creating the initial build with CMake
  • For each unit test:
    • Satisfy compile errors to make the test fail.
    • Implement just enough to make the test pass.
    • Refactor your implementation to enhance readability, reduce duplication, etc.
    • Uncomment the next test

Creating the Initial Build with CMake

Each exercise will bring a CMakeLists.txt file along with the unit tests. It contains the canned CMake recipe to handle the build for you. You should not need to edit this file. The provided recipe assumes that your implementation exists as a header file and a source file named after the exercise.

For instance, the exercise bob expects an implementation in bob.h and bob.cpp. For exercises with dashes in their name, the source files are assumed to use underscores, so word-count expects word_count.h and word_count.cpp. You may decide that your implementation is sufficiently simple that it can live entirely in the header, in which case you can omit the cpp file.

Create your initial implementation files before running CMake. If you do not have files bob.h and bob.cpp when running CMake for exercise bob, then CMake will generate an error about files not being found. These files can be empty, but they must exist.

Using this recipe, CMake can generate a suitable project for your environment by running cmake -G with a suitable generator and the location of the directory for the exercise. CMake will generate a build script appropriate for your operating system. To keep those generated files separate from your exercise source code, it is common to create a directory called build to hold these generated build files, as well as the compiled code. This will keep your exercise folder uncluttered and tidy.

Once the build environment has been created by CMake, you can build your code using the appropriate command for your environment:

  • Linux with make: make
  • Windows with Visual Studio: Select Build / Build Solution from the menu.
  • MacOS with Xcode: Select Build from the toolbar

Examples of running CMake for different environments are shown below.

Linux with Make

The generator name for CMake is Unix Makefiles. Assuming the current exercise is bob and we're in the exercise folder:

$ touch bob.{h,cpp}
$ mkdir build
$ cd build
$ cmake -G "Unix Makefiles" ..
$ make

This example shows creating empty files for the implementation before running CMake.

Simply type make in the build directory to compile the tests. This should generate compile time errors. Once the errors are fixed, make will build and run the tests.

Windows with Visual Studio

Visual Studio has native support for CMake projects, so you should not need to install CMake separately or run it outside of Visual Studio. Follow this guide to setup the CMake project in Visual Studio.

MacOS with Xcode

The generator name for CMake is Xcode. Assuming the current exercise is bob and we're in the exercise folder:

$ touch bob.{h,cpp}
$ mkdir build
$ cd build
$ cmake -G Xcode ..

This example generates the XCode files so that you can open the project in XCode. With the project opened in XCode you may need to add another target. For a new target go to File -> New -> Target from the menu, OS X \ Application \ Command Line Tool -> Next C++ as the language and provide a target name. Run the code using the target.

If your terminal throws an Xcode x.x not supported error, it is highly likely that Xcode is not installed on your machine or that your version is out of date. Please download and install Xcode via the App Store or via this link. Errors similar to The CXX compiler identification is unknown will likely be resolved by following the instructions to install GCC or by adding another target in Xcode as per the above paragraph.