Comprehensive Unit Test Suite Generator

Write a complete suite of unit tests in [TESTING_FRAMEWORK, e.g., Jest, Pytest, JUnit] for the following ⟨LANGUAGE⟩ function/class.

Ensure tests cover:
- The primary happy path
- Key edge cases (null inputs, empty arrays, boundary values, maximum sizes)
- Expected error conditions (invalid arguments, network failures)
- State transitions (if applicable)

Code under test:
```⟨LANGUAGE⟩
[PASTE THE FUNCTION OR CLASS CODE]
```

Structure the tests clearly using describe/it blocks. Mock external dependencies like ⟨DEPENDENCY_NAME⟩ where necessary. Include setup and teardown if needed. Add a brief comment above each test explaining what scenario it validates.