Add unit tests for core application components

[kmuwanga83]

📌 Problem

The project lacks sufficient automated tests.

🎯 Objective

Improve reliability by adding unit tests.

✅ Tasks

• Add tests for core logic
• Add tests for APIs or services
• Ensure tests run successfully

🧪 Acceptance Criteria

• Tests can be executed successfully
• Core features are covered
• Documentation includes how to run tests