[In your CMakeLists.txt define](https://github.com/catchorg/Catch2/blob/devel/docs/cmake-integration.md#cmake-integration):
```cmake
find_package(Catch2 3 REQUIRED)
# These tests can use the Catch2-provided main
add_executable(tests test.cpp)
target_link_libraries(tests PRIVATE Catch2::Catch2WithMain)
# These tests need their own main
add_executable(custom-main-tests test.cpp test-main.cpp)
target_link_libraries(custom-main-tests PRIVATE Catch2::Catch2)
```