mutineer SKILL.md skillA
mutineer from davidteren/mutineer is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.
mdr add davidteren/mutineer/mutineer@git:20261026.80198dfPins git:20261026.80198df in mdr.lock. Pin the fingerprint instead.
- Audit grade
- A, 17 of 17 checks passed
- Kind
- SKILL.md skill
- Repository
- davidteren/mutineer
- Path
skills/mutineer/SKILL.md- Versions recorded
- 8
- Latest version
- git:20261026.80198df, committed Oct 26, 2026
- First version recorded
- Oct 6, 2026
- Size
- 4,834 bytes
- Repository stars
- 72
- License
- MIT
Mutation testing for Ruby (Prism + stdlib, zero deps). Mutates source one change at a time, runs the suite against each mutant, and reports the mutants tests fail to catch, with a versioned JSON contract and CI/agent gating. Use when checking whether a Ruby test suite would catch a change, finding weak or missing tests, gating CI on a mutation score, or acting on mutineer's JSON report.
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
# Mutineer Mutation testing for Ruby, built for CI gates and AI coding agents. Line coverage tells you which code *ran*; mutation testing tells you whether your tests would *notice if it broke*. ## Install ```sh gem install mutineer ``` ## Run ```sh mutineer run <source...> [--test <test>...] [options] # no --test: pairs each source with its test by convention; unmatched sources are skipped; --dry-run with --rails/--boot needs --test ``` Example — mutate `lib/calculator.rb`, gate CI below 90%: ```sh mutineer run lib/calculator.rb --test test/calculator_test.rb --threshold 90 ``` ## Agent loop 1. Edit code and tests on a branch. Fetch `origin/main` before using it below. 2. Run diff-scoped, as JSON: ```sh mutineer run app/ --since origin/main --threshold 90 --format json --output .mutineer/run.json ``` 3. Parse `survivors[]` — each carries a `diff` and an `id`. File moves, renames, project-root changes, and changes to repeated-name or repeated-mutation order can change ids; see [Mutant ids](https://github.com/davidteren/mutineer/blob/main/docs/results.md#mutant-ids). Review each change …
Read the whole file at its exact version.
How to install
mdr add davidteren/mutineer/mutineer@sha256:7034b13dc4e4cb00The line at the top of this page pins the label git:20261026.80198df, 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_t7viocfi7jlmxqls)
1 badge image fetches in 30 days. What the badge shows.
Versions
The registry has recorded 8 versions of this file, between Oct 6, 2026 and Oct 26, 2026, about one every 3 days.
| version | committed | commit | size | audit | |
|---|---|---|---|---|---|
| git:20261026.80198df latest | 2026-10-26 | 80198df | 4,834 B | A | view · diff |
| git:20261025.ba9e0ef | 2026-10-25 | ba9e0ef | 4,660 B | A | view · diff |
| git:20261025.79ebd8e | 2026-10-25 | 79ebd8e | 4,522 B | A | view · diff |
| git:20261024.18ef483 | 2026-10-24 | 18ef483 | 4,389 B | A | view · diff |
| git:20261023.5e17e1d | 2026-10-23 | 5e17e1d | 4,295 B | A | view · diff |
| git:20261016.a03aa0b | 2026-10-16 | a03aa0b | 3,877 B | A | view · diff |
| git:20261008.477889d | 2026-10-08 | 477889d | 3,807 B | A | view · diff |
| git:20261006.2726f9f | 2026-10-06 | 2726f9f | 3,340 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 (4834 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
davidteren/mutineer · 72 stars · license MIT · pushed 2026-11-02 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_t7viocfi7jlmxqls GET https://markdownregistry.com/api/v1/resolve?ref=davidteren/mutineer/mutineer GET https://markdownregistry.com/api/v1/blob/7034b13dc4e4cb00ad1d073d0138a9385cc5c8017c380424c6547e2a4f95187e
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.