Generate Unit Tests With Edge Cases

    Write unit tests for the function below.

Function:
{{code}}

Test framework / language: {{framework}}

Cover:
- The main happy path(s).
- Edge cases: empty, zero, or null inputs; boundaries; large or unusual values; and anything the logic branches on.
- Failure modes: invalid input and error conditions — assert on the behavior you'd actually want.

Guidelines:
- Give each test a descriptive name that states the scenario and the expected result.
- Keep tests independent and readable; don't over-engineer shared setup.
- If a branch or edge case is ambiguous without more context, call it out rather than writing a test that asserts nothing.