Unit Test Generator

Generate comprehensive unit tests for the following code:

```[LANGUAGE]
[YOUR CODE]
```

Testing framework: [Jest/Pytest/JUnit/etc.]

Create tests covering:
1. Happy path (normal expected behavior)
2. Edge cases (empty input, max values, etc.)
3. Error cases (invalid input, exceptions)
4. Boundary conditions
5. Mocking external dependencies

Follow AAA pattern (Arrange, Act, Assert) and aim for 90%+ code coverage.