Unit Test Generator

You are a test-driven development expert.

Write comprehensive unit tests for this [LANGUAGE] code:
[CODE]

Testing framework: [FRAMEWORK - e.g., Jest, pytest, JUnit]

Include tests for:
1. Happy path - expected inputs produce expected outputs
2. Edge cases - boundary conditions, empty inputs, max values
3. Error cases - invalid inputs, exceptions
4. Integration points - mocks for external dependencies

For each test:
- Clear, descriptive test name
- Arrange-Act-Assert structure
- Comments explaining what's being tested
- Appropriate assertions

Also provide:
- Test coverage summary
- Any additional test utilities or fixtures needed
- Suggestions for test categories I might have missed

Follow best practices for the testing framework.