Game of Life refactoring kata in Python

Refactor Conway's Game of Life toward the Liskov Substitution Principle without changing its behavior. Setup is complete when all five starter tests pass.

Overview

This kata complements Clean Code: SOLID, Ep. 11 - Liskov Substitution Principle.

This repository contains two exercises designed to improve your skills in code refactoring, with a focus on the Liskov Substitution Principle (LSP).

Instructions

Exercise 1

The Game of Life is a cellular automaton devised by the British mathematician John Horton Conway in 1970. The game is a zero-player game, meaning that its evolution is determined by its initial state, requiring no further input.

You have a code base that simulates the Game of Life, but it does not adhere to the LSP. Your task is to refactor the code to align with the LSP. This means, among other things, that you should be able to replace any instance of a parent class with an instance of one of its child classes without altering the correctness of the program.

Instructions:

1. Review the current code base and identify parts that violate the LSP.
2. Refactor the violating code to align with the LSP.
3. Make sure all the tests still pass after your refactoring.

Be sure to run the tests before and after your refactoring to make sure you haven't changed the game's behavior.

Exercise 2

For those who complete the refactoring in the first part of the class, a second exercise is available. Your task is to extend the original code with new types of cells.

Here are the new cell types to implement:

1. Immortal Cell: This cell type never dies. Once born, it stays alive through all the subsequent generations.
2. Reproductive Cell: This cell type reproduces faster than a normal cell. It can make a new cell in the neighborhood with two or three neighbors instead of exactly three.
3. Lazy Cell: This cell type requires more neighbors to survive. It stays alive only if it has exactly three neighbors.

Setup is complete when the existing test suite passes.

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/game-of-life-refactoring-python-kata.git

2. Enter the repository directory:

   cd game-of-life-refactoring-python-kata

3. Run the existing 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 5 passed.

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

Work on the kata

Start in game.py. The existing behavior is covered by test_game.py.

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 passes.

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 command reference
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