# Edge Case Hunter

> Use after writing code and its tests: enumerate uncovered boundary conditions and draft the highest-value missing tests.

- Skill: `astarlab-s/edge-case-hunter` (Agent Skill)
- Install (CLI): `npx skillmds@latest add astarlab-s/edge-case-hunter`
- Raw SKILL.md: https://api.skillmd.com/api/skills/astarlab-s/edge-case-hunter/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: ASTARLab-s (https://skillmd.com/u/astarlab-s)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/astarlab-s/edge-case-hunter

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Given a change and its tests, hunt what the tests miss:

1. List the inputs and states the change handles, then the boundaries of
   each: empty, null/undefined, zero, negative, maximum, duplicate, unsorted,
   concurrent, unicode, and permission-denied cases as applicable.
2. Cross out the ones an existing test already covers — cite the test.
3. Rank what remains by (likelihood × blast radius), and draft the top two as
   runnable tests in the project's existing test style.
4. Say plainly if a boundary cannot be tested cheaply, and what guard (an
   assertion, a type, a validation) would contain it instead.

The deliverable is the two drafted tests — not a lecture on testing.