All the Python packages mentioned in CONTRIBUTIONS.md are declared in the `[project.optional-dependencies]` section under a `test` group.
To install the test dependencies, you can now run:
```sh
pip install -e ".[test]"
```
The advantage of using `pyproject.toml` with optional dependencies is that:
- It keeps your testing dependencies separate from any future runtime dependencies
- It's the modern Python standard ([PEP 621](https://peps.python.org/pep-0621/))
- It makes dependency management cleaner and more maintainable
- Other developers can easily install all testing dependencies with a single command
NOTE: Since this repository isn't actually a Python package to be installed (it's just a repository that needs dependencies), we tell setuptools not to discover any package in `[tool.setuptools]`.
