Python library fixture

This independent snapshot supports its numbered hands-on exercise. Run commands from this library directory so application_core, infrastructure, and console are importable. Do not add machine-specific import paths.

python -m unittest discover -s tests -p "test_*.py" -v
python console/main.py

The pytest exercise can also collect the existing unittest cases after pytest is installed in the selected virtual environment. Use python -m pytest -q tests.

Read the methods actually present before describing implemented features. JSON loading and persistence have deliberate limitations; printed errors do not prove recovery. Return/renew actions may change data in this copy. Save actual test output and restore only the copied files. No coverage percentage is claimed.