CMake: How to reuse the same test_main.cpp for each test

Question

I would like to use the test framework Catch2 in a monorepo in which there will be many components, each with their own tests. I'd like to use CMake to define all build targets.

Catch2 provides a simple means to generate a common main() function that will run all tests linked into the application. The source file (which I am calling test_main.cpp) is just these two lines:

#define CATCH_CONFIG_MAIN
#include "catch.hpp"

I'd like to have just one copy of test_main.cpp in my source tree, and refer to it from each component directory that has tests (which will end up being on the order of hundreds of directories).

I can see how to set up CMake to work if I duplicated the test_main.cpp so that a redundant copy existed in each directory with tests, but I haven't figured out how to have just one copy. Is there a simple trick I've overlooked?

[Git can handle symlinks FWIW](https://stackoverflow.com/questions/954560/how-does-git-handle-symbolic-links). — ivan_pozdeev, Mar 16 '18 at 02:38
I would check the Catch's logic to find out where it looks for test sources. Since they are all plain C code (i.e. Catch seems to only kick in after compilation), I guess it's as simple as adding another compilation unit to a project. — ivan_pozdeev, Mar 16 '18 at 02:42
Have you tried just adding `test_main.cpp` to each `add_executable` line? You'd probably need the full path to the file, but something like `${PROJECT_SOURCE_DIR}/test_main.cpp` (assuming you have `test_main.cpp` at the top level of your project) should work. — Stephen Newell, Mar 16 '18 at 03:02

sakra · Accepted Answer · 2018-03-16T11:01:09.507

Try integrating Catch2 as a CMake interface library in the following way:

Add the single header file catch.hpp and test_main.cpp to a directory of their own (e.g., Catch2) along with the following CMakeLists.txt:

add_library(catch INTERFACE)
target_include_directories(catch INTERFACE $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>)
target_sources(catch INTERFACE "${CMAKE_CURRENT_SOURCE_DIR}/test_main.cpp")

The in your outermost CMakeLists.txt include Catch2 with add_subdirectory:

add_subdirectory(Catch2)

You can then set up test executables anywhere in the project in the following way:

add_executable(
    project_tests EXCLUDE_FROM_ALL
    test_case1.cpp
    test_case2.cpp
    ...
)

target_link_libraries(project_tests catch)

Because test_main.cpp has been added to catch as an interface source file, it will be compiled as part of the test executable.

This looks good. I'll give it try and approve the answer after I've verified that it works. Thanks. — 4dan, Mar 22 '18 at 03:42
in fact we do not need to copy catch.hpp and put it to a directory with test_main.cpp, we can just have test_main.cpp in the folder and write CMakeLists.txt like:``` add_library(catch test_main.cpp) target_link_libraries(catch PUBLIC Catch2::Catch2) ``` — BruceSun, Jul 25 '20 at 07:16

CMake: How to reuse the same test_main.cpp for each test

1 Answers1