Test scripts are named test_xxx.py. Helper classes and functions can be found in helper.py.
Install:
python3 -m pip install pytest pytest-cov pytest-timeout
To run an individual test:
pytest Tests/test_image.py
Or:
pytest -k test_image.py
Run all the tests from the root of the Pillow source distribution:
pytest
Or with coverage:
pytest --cov PIL --cov Tests --cov-report term coverage html open htmlcov/index.html