[contract] Write comprehensive unit tests for core contract logic (Part 1)

[starTecchie]

Description

Implement and refine the following task: Write comprehensive unit tests for core contract logic within the contract environment.

Requirements and context

• Code must follow project guidelines and existing design patterns.
• Ensure all edge cases are considered.
• Refer to the issueTemplate.md for quality standards.

Suggested execution

1. Fork the repo and create a branch feature/test-task-16
2. Implement the necessary code changes in the contract directory.
3. Write associated tests to prove your solution works.
4. Document any new functions or architecture changes.

Guidelines

• Assignment required before starting.
• Complexity Level: Medium (150 points)