mojo-pytest

Mojo🔥 language test runner plugin for pytest. Try it for your mixed Python and Mojo codebases!

Design

This package implements a pytest plugin to discover and run Mojo tests, alongside your Python tests. Although pytest does not have any awareness of Mojo source or package structure, pytest is extensible. In summary, plugin.py calls mojo test in a sub-process and parses the outputs and exit codes.

Usage

1. Create your Mojo tests according to the manual: https://docs.modular.com/mojo/tools/testing .

2. Install pytest and pytest-mojo plugin using the pyproject file:

   # (optional) create and activate a virtualenv
   python3 -m venv venv/
   source venv/bin/activate
   
   # install from github
   pip install git+https://github.com/guidorice/mojo-pytest.git
   
   # or install from cloned repository
   pip install .
   
   # verify pytest and the Mojo plugin are installed
   pytest --version
   pip show pytest-mojo

3. See the example project for one possible filesystem layout:

   • example_src/ has it's tests in the example_tests/ folder.
   • Remember the Mojo manual explains that tests are allowed to be in the same folder as Mojo code, or different folder, or even as Mojo code in docstrings! So this example project is just one possibility.

4. Mojo tests and Python tests are all run via pytest! Use the plugin's --mojo-include option to include your Mojo packages.

   # this example_src/ contains a Python package which is also called from Mojo,
   # so we must add it using PYTHONPATH. Please note that the full path may be required!
   $ export PYTHONPATH=/Users/you/project/example_src/
   
   # Use the plugin's --mojo-include option to tell mojo where to find `my_package` 
   $ pytest --mojo-include example_src/ example_tests/
   
   ================================ test session starts ================================
   platform darwin -- Python 3.11.9, pytest-8.2.2, pluggy-1.5.0
   rootdir: /Users/you/project
   plugins: mojo-24.4.0
   collected 6 items                                                                   
   
   example_tests/my_package/my_test.mojo .                                       [ 16%]
   example_tests/my_package/test_fibonacci.mojo ..                               [ 50%]
   example_tests/my_package/test_fibonacci.py .                                  [ 66%]
   example_tests/my_package/test_fire.🔥 .                                       [ 83%]
   example_tests/my_package/test_random_tensor.mojo .                            [100%]
   
   ================================= 6 passed in 6.47s =================================

   👆🏽 Notice how your Python tests are run alongside your mojo tests.

5. Mojo binary packages are also supported with --mojo-include. For example, this could be used in a CI/CD script:

   $ mojo package example_src/my_package -o build/my_package.mojopkg  # or .📦
   $ pytest --mojo-include build/ example_tests/
   ... 
   ... (same pytest output as above)
   ...

See also, the pytest docs for many more options.

Example Project

In the example_src/ directory is a Mojo package with a couple of modules. There is also a Python module, which we call in two ways (from pytest, and from Mojo). Here is an overview:

example_src
├── main.mojo                    # main entry point. run with `mojo example_src/main.mojo`
└── my_package
    ├── __init__.mojo            # this is both Mojo package, and a Python package.
    ├── __init__.py
    ├── fibonacci.mojo           # Mojo implementation
    ├── fibonacci.py             # Python implementation
    └── random_tensor.mojo       # random tensor stuff

example_tests
└── my_package
    ├── my_test.mojo             # files can be named xxx_test as well as test_xxx.
    ├── test_fibonacci.mojo      # tests the Mojo impl and the Python impl.
    ├── test_fibonacci.py        # tests the Python impl (pure Python).
    ├── test_fire.🔥             # tests are collected for fire extension too.
    └── test_random_tensor.mojo  # tests the Mojo impl.

Links

• Writing tests in Mojo: https://docs.modular.com/mojo/tools/testing .
• Non-Python tests in pytest: https://pytest.org/en/7.4.x/example/nonpython.html#non-python-tests
• C test runner: https://pytest-c-testrunner.readthedocs.io/
• Pytest docs: https://docs.pytest.org