# Receipt

> Verify that a requested bug fix changes observable behavior with a failing-before, passing-after reproduction and honest execution evidence.

- Skill: `soongwan/receipt` (Agent Skill, multi-file: 8 files)
- Install (CLI): `npx skillmds@latest add soongwan/receipt`
- Raw SKILL.md: https://api.skillmd.com/api/skills/soongwan/receipt/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: SoonGwan (https://skillmd.com/u/soongwan)
- Updated: 2026-09-22
- Page: https://skillmd.com/skills/soongwan/receipt

---


# Receipt

> You fixed it? Show me the receipt.

Reuse supplied guidance; discover missing instructions only within authorized roots, never through an out-of-scope ancestor sweep. Report inaccessible evidence instead of broadening access.

For a current bug, select a regression on the actual affected path using the documented runner. Reuse valid before evidence; otherwise observe the defect-specific failure, implement the requested fix, then rerun unchanged assertions/inputs. Preserve neighboring behavior and required coverage. Inspect history only for unresolved behavior or implementation.

For an already-present fix, compare isolated versions with the same current assertions/inputs and compatible runtime; identify the code loaded by the test process. Reuse an adequate project-native comparison instead of rebuilding it. Optional support for [Python](references/existing-fix.md) or [native Node tests](references/node-comparison.md) supplies copying, source checks and cleanup when those are missing. Choose by the required evidence and setup work, not merely by language support. Don't reverse patches in the user's working tree.

A required suite running that regression with matching inputs/runtime supplies after evidence; don't repeat it separately. Skipped, undiscovered or differently configured tests don't qualify. Changed relevant inputs invalidate reused results.

Batch final checks in one shell call, adapting the runner and paths:

```sh
python3 -B -m unittest -v && git diff --check -- app.py test_app.py && git diff -- app.py test_app.py
```

`&&` leaves later checks unrun after failure. If all must run, retain each exit explicitly, not just the shell's final status. Review untracked files separately; `git diff` omits them.

Setup failures aren't defect reproduction; mocks don't prove unobserved effects. Preserve user changes and scope; verification alone authorizes neither implementation nor publication.

Report the reviewed change, decisive before/after observations and commands, applicable revision identities and limits. Stop when the requested outcome and required checks are verified; no separate dossier or unrelated green checks.