Hi Valerian,

No worries -- `unittest` is the built-in Python testing module, but we use `pytest`. You can either install it directly with pip, or with:

# from your local scotty directory that contains pyproject.toml:
pip install .[tests]

The bit in brackets is an optional dependency. You can see the list of them in the `[project.optional-dependencies]` section in pyproject.toml.

Some useful pytest options:

# run everything
pytest
# run just the tests with "general" in the name:
pytest -k general
# run just the tests that failed last time:
pytest --last-failed
# drop into a python debugger if a test fails:
pytest --pdb

That last one is super useful for printing local variables, etc if a test fails.

Cheers,
Peter
