Review unit test coverage for this feature group.

For every feature listed:
- Verify unit tests exist covering every boundary condition, edge case, and error condition.
- Tests must exercise: empty inputs, null/undefined, maximum values, minimum values, off-by-one, type mismatches, concurrent access (if applicable), and error/exception paths.
- Each test should isolate a single behavior.

If tests are missing or incomplete, write them.
Score 0–100 based on edge-case coverage AFTER your fixes.
