engineering-handbook

Python - Tests

For built-in unit and integration tests of our Python projects, we use pytest. Running pytest and ensuring all tests are passing must be part of the CI of all repositories.

Setting up pytest.

To start using pytest, some packages must be added to requirements/ci.txt: pytest and pytest-mock. Note thatpytest-django must also be added for Django projects. To do so, add the following lines to requirements/ci.txt and replace the targeted version with the latest one available.

pytest==<latest_version>
pytest-django==<latest_version>
pytest-mock==<latest_version>

Make sure that in requirements/dev.txt the first line is

-r ci.txt

For the new packages to be added to your docker image, build the image again with

docker-compose build

In your pyproject.toml file, add the following lines.

[tool.pytest.ini_options]
minversion = "6.0"
DJANGO_SETTINGS_MODULE = "repository_name.settings.ci"
addopts = "-x --strict-markers --ds=repository_name.settings.ci"
python_files = ["test*.py", "test_*.py"]

Creates a tests.py file and add the following code.

def test_dummy(client):
    result = 1+1
    assert result == 2

Now enter the container and run the tests.

docker-compose exec app bash
pytest

You should see one passing test.

Reporting test coverage

pytest can report test coverage after running. This is useful to understand which lines of code are covered with tests. We use this feature as part of our automated CI.

To generate an XML coverage report, use the following options when running pytest:

pytest --cov=. --cov-report=xml