How to integrate Catch2 as external library with CMake?

Question

I am trying to set up a learning project using Catch2 and I decided that it was best to clone the repository in a Cpp folder, so I could get updates and use it for other C++ projects. The installing method is as described here .

The basic folder structure is:

Cpp
├───TestProject
│   ├───main.cpp
│   ├───.vscode
│   └───build
│       ├───CMakeFiles
│       └───Testing
└───Catch2
   ├─── ...
  ...

As per Catch2 documentation I put this on my CMake file:

find_package(Catch2 REQUIRED)
target_link_libraries(tests Catch2::Catch2)

However, when I try to configure the project in VS Code, I get the following error message:

[cmake] CMake Error at CMakeLists.txt:5 (target_link_libraries):
[cmake]   Cannot specify link libraries for target "tests" which is not built by this
[cmake]   project.

main.cpp is just a Hello World file and the complete CMakeLists.txt file contents are:

cmake_minimum_required(VERSION 3.0.0)
project(TestProject VERSION 0.1.0)

find_package(Catch2 REQUIRED)
target_link_libraries(tests Catch2::Catch2)
enable_testing()

add_library(TestProject TestProject.cpp)

set(CPACK_PROJECT_NAME ${PROJECT_NAME})
set(CPACK_PROJECT_VERSION ${PROJECT_VERSION})
include(CPack)

I am unsure why this happens. I am a complete newcomer to CMake, save for very basic commands I had to use at work. I guess it would be less work to just drop it as a header file like it's intended to, but this approach made more sense to me...

Note: I have read this SO question . However his question had to do with Catch2 as a header file inside the project.

Note 2: desired behaviour is to build the project using Catch2 as an external library.

(Additional information: CMake --version is 3.13.3, using CMakeTools in VS Code, OS is Windows 10)

Answer 1

First, since the library has been installed through CMake (same applies for installs using a package manager), it is recommended to flag find_package with CONFIG (read about Config mode here ). This is because even if Catch2 repository is in a parent, common folder to the project, the CMake installation process installs it in your Program Files folder (in Windows); ie the repository is just that.

Additionally you should add_executable(tests main.cpp) so CMake has "tests" as a target. This solves the original problem.

However, for it to completely work, you need to follow these additional steps:

1. Use catch_discover_tests(tests)
2. include(CTest) possibly necessary.
3. The include preprocessor command should be: #include <catch2/catch.hpp> instead of simply #include "catch.hpp" .

Also, make sure your editor is aware of the environmental variables created during the installation of Catch2. That is, if you are having problems, restart the editor so it re-reads environmental variables.

Full CMakeLists.txt:

cmake_minimum_required(VERSION 3.5.0)
project(TestProject LANGUAGES CXX VERSION 0.1.0)

find_package(Catch2 REQUIRED)
add_executable(tests main.cpp) # solution to the original problem
target_link_libraries(tests Catch2::Catch2)

include(CTest) # not sure if this is 100% necessary
include(Catch)
catch_discover_tests(tests)
enable_testing()

Note: Instead of add_executable , we should use add_library , although no tests are recognized in library mode for some reason; however that is beyond the scope of this question as it lies more in the knowledge of use pf Catch2.