test-mutation SKILL.md skillA
This file is byte-identical to the first copy the registry indexed. Same content hash, so the same checks give both the same grade.
test-mutation from kensaurus/skills is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.
mdr add kensaurus/skills/test-mutation@git:20261009.3771283Pins git:20261009.3771283 in mdr.lock. Pin the fingerprint instead.
- Audit grade
- A, 17 of 17 checks passed
- Kind
- SKILL.md skill
- Repository
- kensaurus/skills
- Path
skills/test-mutation/SKILL.md- Versions recorded
- 5
- Latest version
- git:20261009.3771283, committed Oct 9, 2026
- First version recorded
- Aug 18, 2026
- Size
- 7,308 bytes
- Repository stars
- 9
- License
- MIT
Run mutation testing (StrykerJS, mutmut) to measure whether tests assert behavior, not just execute lines. Use when "add mutation testing", "are our tests real", "can our test suite be gamed", or after an agent bulk-generated tests.
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
# test-mutation — Coverage proves the test ran; mutants prove it would notice **Degree of freedom: MIXED** — scope and triage `[HIGH freedom]`; first run and CI floor `[LOW freedom — measure, then ratchet]`. Never start with the whole repo. Install and run the gate coverage cannot close. **Coverage proves the test *ran* the code; mutation testing proves the test would *notice* if the code were wrong.** The tool makes hundreds of small deliberate bugs (mutants) — flip `>` to `>=`, delete a statement, replace a return — and reruns the tests. Survivors mark code the tests execute but verify nothing. This is the specific counter to agent-generated suites: an agent can trivially produce 90% coverage with no meaningful assertions, and every coverage ratchet will wave them through. Mutants do not care about coverage theater. ## This skill vs neighbors | Skill | Owns | |---|---| | **test-mutation** (this) | Install / run / triage mutation testing; score ratchet | | `plan-test-coverage` | What *should* be tested — plan only, no harness | | `test-unit` | Write the tests | | `audit-gate-logic` / `housekeep-gates` | Ratchet policy this score plugs into | …
Read the whole file at its exact version.
How to install
mdr add kensaurus/skills/test-mutation@sha256:967271dc2b6bcbdfThe line at the top of this page pins the label git:20261009.3771283, 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_4q35lnjmlx65dr2v)
2 badge image fetches in 30 days. What the badge shows.
Versions
The registry has recorded 5 versions of this file, between Aug 18, 2026 and Oct 9, 2026, about one every 13 days.
| version | committed | commit | size | audit | |
|---|---|---|---|---|---|
| git:20261009.3771283 latest | 2026-10-09 | 3771283 | 7,308 B | A | view · diff |
| git:20260923.68c095e | 2026-09-23 | 68c095e | 7,285 B | A | view · diff |
| git:20260910.2cc3ce5 | 2026-09-10 | 2cc3ce5 | 7,366 B | A | view · diff |
| git:20260819.170df67 | 2026-08-19 | 170df67 | 7,344 B | A | view · diff |
| git:20260818.6723100 | 2026-08-18 | 6723100 | 5,900 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 (7308 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
kensaurus/skills · 9 stars · license MIT · pushed 2026-10-19 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_4q35lnjmlx65dr2v GET https://markdownregistry.com/api/v1/resolve?ref=kensaurus/skills/test-mutation GET https://markdownregistry.com/api/v1/blob/967271dc2b6bcbdf7001d2e1299088003fbe3d172dd3718f1501cc7c174cc01c
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.
More from kensaurus/skills
Every file in kensaurus/skills