CMake, Python and Pytest

April 28, 2022

Python can easily be used from CMake, perhaps to simplify test scripts for continuous integration. Python scripts are managed in CMakeLists.txt. First, find Python interpreter:

find_package(Python COMPONENTS Interpreter REQUIRED)

Then to run a simple Python script in a CMake test:

add_test(NAME MatmulPython
COMMAND ${Python_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/matmul.py
)

To use PyTest:

add_test(NAME MatmulPython
COMMAND ${Python_EXECUTABLE} -m pytest ${CMAKE_CURRENT_SOURCE_DIR}
)

That will look under tests/test*.py by default.

From the project directory:

cmake -B build -S .

-S .: relative path to CMakeLists.txt e.g. -S src

This generates the makefile, but does not compile anything, since CMake is a build script generator.

Compile:

cmake --build build --parallel

--parallel: Compile code in parallel, if possible.

This uses the appropriate compilers and linkers to generate the executables and libraries.

Execute self-tests you’ve defined with add_test() in CMakeLists.txt:

ctest --test-dir build -V

If that’s too verbose, try:

ctest --test-dir build --output-on-failure

For faster testing by defaulting to running multiple tests in parallel, set CTEST_PARALLEL_LEVEL environment variable.