[Feature] add test code for game logic

[KoreAustralian]

Description

This PR adds comprehensive unit tests for the core game modules to improve code reliability and support future refactoring

Type of change

Please delete options that are not relevant.

• [ V ] Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

ran the test code to verify all new test codes pass

Checklist:

• [ V ] I have followed the coding style guidelines of this project
• [ V ] I have reviewed my own code
• I have commented hard-to-understand areas of my code
• [ V ] I have added docstrings to all public functions/methods
• [ V ] I have used descriptive variable names to make by code easier to understand
• I have made corresponding changes to the documentation
• [ V ] I have added tests that prove my fix is effective or that my feature works
• [ V ] New and existing unit tests pass locally with my changes

Related Issue(s)

Closes #48