Lab: Test and protect the shelf's code

Module 10 · Lab · About 60 minutes · Needs: lessons 1 to 4 of this module, and the Module 9 lab (the booknook folder in your Drive, with models.py)

What you are building

Amira's request for this module is "Make sure it never breaks." The four lessons gave you the tools: generators (Lesson 1), decorators (Lesson 2), context managers (Lesson 3) and pytest (Lesson 4).

This lab puts all four into the project. A new module, booknook/tools.py, holds a generator of overdue loans, a log_calls decorator applied to Library.lend and Library.return_book, and a safe_save context manager. A new folder, tests/, holds four test files that check every rule, edge cases included. Then pytest runs them and mypy checks the package's hints.

Open a new Colab notebook, call it module-10-lab.ipynb, and run each cell in order.