Implement Testing for Game Engine

As a developer, I want to ensure that all parts of the game engine work as expected, so that any bugs or issues can be identified and fixed promptly.

• Write unit tests for the Python code execution function.
• Write tests for the puzzle loading and displaying function.
• Write tests for the solution checking function.
• Write tests for the progress tracking and scoring system.
• Workflows - automate testing to run all tests whenever code is updated.