Contributing to Catch

So you want to contribute something to Catch? That‘s great! Whether it’s a bug fix, a new feature, support for additional compilers - or just a fix to the documentation - all contributions are very welcome and very much appreciated. Of course so are bug reports and other comments and questions.

If you are contributing to the code base there are a few simple guidelines to keep in mind. This also includes notes to help you find your way around. As this is liable to drift out of date please raise an issue or, better still, a pull request for this file, if you notice that.


Ongoing development is currently on master. At some point an integration branch will be set-up and PRs should target that - but for now it's all against master. You may see feature branches come and go from time to time, too.

Directory structure

Users of Catch primarily use the single header version. Maintainers should work with the full source (which is still, primarily, in headers). This can be found in the include folder. There are a set of test files, currently under projects/SelfTest. The test app can be built via CMake from the CMakeLists.txt file in the root, or you can generate project files for Visual Studio, XCode, and others (instructions in the projects folder). If you have access to CLion, it can work with the CMake file directly.

As well as the runtime test files you'll also see a SurrogateCpps directory under projects/SelfTest. This contains a set of .cpp files that each #include a single header. While these files are not essential to compilation they help to keep the implementation headers self-contained. At time of writing this set is not complete but has reasonable coverage. If you add additional headers please try to remember to add a surrogate cpp for it.

The other directories are scripts which contains a set of python scripts to help in testing Catch as well as generating the single include, and docs, which contains the documentation as a set of markdown files.

When submitting a pull request please do not include changes to the single include, or to the version number file as these are managed by the scripts!

Testing your changes

Obviously all changes to Catch's code should be tested. If you added new functionality, you should add tests covering and showcasing it. Even if you have only made changes to Catch internals (i.e. you implemented some performance improvements), you should still test your changes.

This means 2 things

  • Compiling Catch's SelfTest project:
$ cd Catch2
$ cmake -Bdebug-build -H. -DCMAKE_BUILD_TYPE=Debug
$ cmake --build debug-build

because code that does not compile is evidently incorrect. Obviously, you are not expected to have access to all the compilers and platforms supported by Catch2, but you should at least smoke test your changes on your platform. Our CI pipeline will check your PR against most of the supported platforms, but it takes an hour to finish -- compiling locally takes just a few minutes.

  • Running the tests via CTest:
$ cd debug-build
$ ctest -j 2 --output-on-failure

If you added new tests, approval tests are very likely to fail. If they do not, it means that your changes weren't run as part of them. This might be intentional, but usually is not.

The approval tests compare current output of the SelfTest binary in various configurations against known good outputs. The reason it fails is, usually, that you've added new tests but have not yet approved the changes they introduce. This is done with the scripts/ script, but before you do so, you need to check that the introduced changes are indeed intentional.

this document is still in-progress...