lethal-mutation-testing SKILL.md skillA
lethal-mutation-testing from sshadows/lethal is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.
mdr add sshadows/lethal/lethal-mutation-testing@git:20261106.0937045Pins git:20261106.0937045 in mdr.lock. Pin the fingerprint instead.
- Audit grade
- A, 17 of 17 checks passed
- Kind
- SKILL.md skill
- Repository
- sshadows/lethal
- Path
skills/lethal-mutation-testing/SKILL.md- Versions recorded
- 5
- Latest version
- git:20261106.0937045, committed Nov 6, 2026
- First version recorded
- Sep 27, 2026
- Size
- 8,399 bytes
- Repository stars
- 10
- License
- MIT
Run LethAL mutation testing against a Business Central AL project and read the result. Use when asked whether an AL test suite actually catches bugs, to find weak or missing tests, or to check a suite before trusting a coverage number. Publishes a changed build to a BC server, so it needs a sandbox or dev container and is user-invoked.
Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file the same grade.
What the file says
# LethAL mutation testing LethAL breaks AL code on purpose, one small change at a time, and runs the test suite against each break. A change the tests catch is **killed**; one they miss is a **survivor**; one no test executes is **no-coverage**. It answers what coverage cannot: not "did this line run" but "would anyone notice if it were wrong". Full reference: `docs/using-lethal-from-an-agent.md` in the LethAL repository. ## Safety, before anything else - **Sandbox or dev container only. Never a production tenant.** The changed build stays published until the user republishes their own app. - The user's source tree is never modified; LethAL mutates a copy in a scratch directory. - `--stop-hung-sessions` lets LethAL end a BC session on the user's server, so it needs their yes. Ask for it ONCE, up front, and recommend it on a sandbox: a mutant that turns a loop into an infinite one is ordinary on real code (`remove-assignment` on a loop's exit flag did it twice in one run), and without the flag each one costs the whole budget, a quarantine, and a full redeploy-and-baseline on `--resume`, roughly ten minutes on a hosted sandbox. With it the same …
Read the whole file at its exact version.
How to install
mdr add sshadows/lethal/lethal-mutation-testing@sha256:b72a73635a65f4f1The line at the top of this page pins the label git:20261106.0937045, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.
[](https://markdownregistry.com/a/art_j3uev7t4ytetddsw)
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Versions
The registry has recorded 5 versions of this file, between Sep 27, 2026 and Nov 6, 2026, about one every 10 days.
| version | committed | commit | size | audit | |
|---|---|---|---|---|---|
| git:20261106.0937045 latest | 2026-11-06 | 0937045 | 8,399 B | A | view · diff |
| git:20261025.288c0c9 | 2026-10-25 | 288c0c9 | 8,399 B | A | view · diff |
| git:20261020.a3f6623 | 2026-10-20 | a3f6623 | 8,399 B | A | view · diff |
| git:20260929.4f14348 | 2026-09-29 | 4f14348 | 8,399 B | A | view · diff |
| git:20260927.62c3a45 | 2026-09-27 | 62c3a45 | 8,399 B | A | view |
Audit of the latest version
- pass: Frontmatter block present
- pass: Frontmatter declares a name
- pass: Frontmatter declares a description
- pass: Size between 200 bytes and 200 KB (8399 bytes)
- pass: No zero-width or bidi control characters
- pass: No instruction hidden inside an HTML comment
- pass: No link to an exfiltration or paste host
- pass: No credential-shaped string
- pass: No instruction to send local credentials anywhere
- pass: No text hidden with inline styles
- pass: No prompt-injection phrasing
- pass: No curl or wget piped into a shell
- pass: No recursive delete of root, home or parent
- pass: No instruction to read or print local credentials
- pass: No base64 blob over 200 characters
- pass: No link to a raw IP address
- pass: No script tag
Source
sshadows/lethal · 10 stars · license MIT · pushed 2026-11-07 · branch master
API
GET https://markdownregistry.com/api/v1/artifacts/art_j3uev7t4ytetddsw GET https://markdownregistry.com/api/v1/resolve?ref=sshadows/lethal/lethal-mutation-testing GET https://markdownregistry.com/api/v1/blob/b72a73635a65f4f102bb9cab551c18e19c43d9756942c3c444de87b61a255b48
Your AI assistant does the legwork. You hear about the deals worth your word. Hand yours the standing instructions at modelranch.com and it joins the network that reads files like this one.
Guides: the SKILL.md format and its required fields · what to check before you install a skill · how to pin a skill to an exact version · where to find agent skills · keeping a team on the same skills · which agent file does what.