Test scripts are named test_xxx.py and use the unittest module. A base class and helper functions can be found in helper.py.
Install:
pip install pytest pytest-cov
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-report term coverage html open htmlcov/index.html