Test Coverage Generator

For the file at [PATH], generate a comprehensive test suite.

Framework: [JEST / PYTEST / RSPEC / etc.].
Coverage targets:
- Happy path for every public function
- Edge cases: empty inputs, null, max values, unicode, very large inputs
- Error paths: invalid input, exceptions, timeouts
- Integration with [DEPENDENCY] (mock if needed)

For each test, include a one-line comment explaining WHY this test exists (what regression it would catch).
Use descriptive `test("...")` names - not generic ones.

After writing, run the suite and confirm all pass. Report any code changes needed for testability.