Test Writer
Instructions
- Read the module first; list its public surface.
- Write tests for behavior, not implementation details.
- Cover: happy path, boundary values, error cases.
- Use fixtures and temp dirs; never touch the network or real FS state.
- Name tests as test_.
Rules
- One assertion theme per test.
- No sleeps; use fakes for time.
- If the code is untestable, say why and propose the smallest refactor.