Smart home refactoring kata in Python

Refactor a smart home controller toward the Dependency Inversion Principle without changing its behavior. Setup is complete when all four starter tests pass.

Overview

This kata complements Clean Code: SOLID, Ep. 13 - Dependency Inversion Principle.

In this exercise, you'll practice refactoring code to adhere to the Dependency Inversion Principle (DIP). You'll be working with a smart home system that controls different types of lights and an air conditioner.

Instructions

Exercise 1

The initial code consists of several device classes and the SmartHomeController class, which is responsible for controlling all the devices (lights and air conditioner).

However, the initial code violates the Dependency Inversion Principle, as the SmartHomeController class directly depends on concrete classes. In the tests, we also directly manipulate the dimmable_light and networkable_light instances to check their unique behaviors.

Your goal is to refactor the code to adhere to the Dependency Inversion Principle and make it easier to implement new devices.

Here are some guidelines to follow:

1. Introduce an interface or several interfaces (or abstract base classes) for the devices that the SmartHomeController interacts with.

2. Update the SmartHomeController class to depend on these abstractions instead of the concrete device classes.

3. Update the devices to implement these interfaces.

4. Modify any constructors or method calls as necessary to accommodate the refactoring.

Note

Remember that in this exercise, we assume all devices are in an ideal state and don't account for error cases such as a network connection failure or an attempt to dim a light below 0% or above 100% brightness.

Make sure the program still behaves the same way after your refactoring. The existing tests check this at a rudimentary level by examining the program's output.

Exercise 2

When you're done with refactoring, test the quality of your refactoring by implementing two additional scenarios (methods) in SmartHomeController:

1. Add the make_quick_breakfast scenario to open the blinds and make a predefined coffee type.

   1. Add a Blinds device class with open and close methods (blinds are always powered and do not have an on/off function).
   2. Add a make_quick_breakfast method to SmartHomeController.

2. Add an automatic vacuum cleaner and the schedule_night_cleaning scenario, which should start cleaning once everything else is turned off.

   1. Add a VacuumCleaner device class with start_cleaning and stop_cleaning methods.
   2. Add a schedule_night_cleaning method to SmartHomeController. After calling this method, the vacuum cleaner should start cleaning once all other devices are turned off.

Evaluate whether your refactoring made life easier for you or not.

Prerequisites

Required:

• Git
• uv

Optional:

• GNU Make, for shorter commands. Every required task also has a direct uv command.

You do not need to install Python or pytest separately. uv installs a compatible Python version and the locked project dependencies when needed.

Set up the kata

1. Clone the repository:

   git clone https://github.com/Coding-Cuddles/smart-home-refactoring-python-kata.git

2. Enter the repository directory:

   cd smart-home-refactoring-python-kata

3. Run the tests. Use Make when it is installed:

   make test

   Otherwise, run pytest through uv directly:

   uv run pytest

   The first run may install Python and the project dependencies. Setup is complete when pytest reports 4 passed.

   If the command fails with uv: command not found, install uv and repeat this step.

Work on the kata

1. Refactor SmartHomeController and its devices in smart_home.py without changing their observable behavior.

2. Run the tests after each change. Use Make when it is installed:

   make test

   Otherwise, run pytest through uv directly:

   uv run pytest

   Continue when the test run completes without failures.

Make command reference

Make is optional. Run make or make help to list these commands in the terminal.

Command	Result
make all	Run the test suite
make help	Show the available Make targets
make test	Run the test suite
make format	Format tracked Python files
make format-check	Check formatting without changing files
make clean	Remove generated caches