Add unit tests for core application functionality

[kmuwanga83]

📌 Problem

The project lacks sufficient automated tests, increasing risk of bugs.

🎯 Objective

Introduce basic unit testing.

✅ Tasks

• Identify core modules
• Add unit tests
• Ensure tests can be executed easily

🧪 Acceptance Criteria

• Tests run successfully
• Core logic is covered
• Instructions for running tests are documented

💡 Suggested Labels

testing, backend, help wanted