mutation-testing

Validate test effectiveness with mutation testing using Stryker (TypeScript/JavaScript with Vitest or bun test via @hughescr/stryker-bun-runner) and mutmut (Python). Find weak tests that pass despite code mutations. Use to improve test quality.

Quality

68%

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Securityby

Passed

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tessl review fix ./plugins/mutation-testing/skills/mutation-testing/SKILL.md

Quality

Content

75%Weight 40%Scale 1-5

Reviews the quality of instructions and guidance provided to agents. Good implementation is clear, handles edge cases, and produces reliable results.

The content is highly actionable with complete executable examples across both ecosystems and a clear workflow with feedback loops. It is held back slightly by redundancy and a monolithic structure that could benefit from splitting reference material.

Suggestions

De-duplicate the Workflow section so it references the commands above rather than restating them, improving conciseness.

Move the mutation-type catalog and detailed config-option tables into a separate reference file linked from the overview to improve progressive disclosure.

Fram the coverage check and survived-mutant review as explicit gated checkpoints ("Only proceed when coverage >= 80%") to push workflow clarity toward 5.

Dimension	Reasoning	Score
Conciseness	The body is mostly efficient with concrete config and commands, but it carries redundancy (the Workflow re-lists commands already shown, and "Improving Weak Tests" overlaps the earlier weak/strong example) that could be tightened.	3 / 5
Actionability	Fully executable install commands, complete config files, run invocations, and worked weak-vs-strong test examples cover the common TS/JS (Vitest and Bun) and Python (mutmut) cases copy-paste ready.	5 / 5
Workflow Clarity	A clear 5-step Workflow includes a coverage pre-check gate and a fix-survived-mutants → re-run incrementally feedback loop, though the validation checkpoints are not framed as hard "only proceed when..." gates.	4 / 5
Progressive Disclosure	The single SKILL.md is well-organized with clear section headers and no external bundle files are needed, but it is a ~150-line monolith where some reference material (e.g. mutation-type catalog, full config options) could be split out.	4 / 5
	Total	16 / 20 Passed

Description

61%Weight 40%Scale 1-5

Based on the skill's description, can an agent find and select it at the right time? Clear, specific descriptions lead to better discovery.

The description clearly conveys a specific niche (mutation testing with Stryker/mutmut) and strong trigger terms, but it lacks an explicit "Use when..." trigger clause, capping completeness. Specificity is solid but not exhaustive.

Suggestions

Add an explicit trigger clause, e.g. "Use when the user asks to assess test quality, find weak tests, or measure mutation score."

Expand the action list with a couple more concrete verbs (e.g. "Generate mutation reports", "Identify surviving mutants") to lift specificity toward 5.

Include common synonyms/extensions ("mutation score", "test mutants") to round out trigger term coverage.

Dimension	Reasoning	Score
Specificity	Names the mutation-testing domain with two concrete actions ("Validate test effectiveness", "Find weak tests that pass despite code mutations") plus tooling, but the action list is not comprehensive and "Use to improve test quality" is generic.	3 / 5
Completeness	It clearly answers what the skill does, but the only "when" guidance is "Use to improve test quality", which is a purpose statement rather than an explicit trigger clause, so completeness is capped at 3 per the rubric.	3 / 5
Trigger Term Quality	Good coverage of natural terms a user would say ("mutation testing", "weak tests", "test quality") alongside specific tool names (Stryker, mutmut, Vitest), though synonyms and file extensions are absent.	4 / 5
Distinctiveness Conflict Risk	Mutation testing with named tools (Stryker, mutmut) is a clear niche with minimal conflict risk, though "test quality" framing overlaps slightly with adjacent testing skills noted in See Also.	4 / 5
	Total	14 / 20 Passed

Validation

93%

Warnings & errors only

Checks the skill against the spec for correct structure and formatting. All validation checks must pass before discovery and implementation can be scored.

Validation — 15 / 16 Passed

Validation for skill structure

Criteria	Description	Result
allowed_tools_field	'allowed-tools' contains unusual tool name(s)	Warning

	Total	15 / 16 Passed

Repository: secondsky/claude-skills
Path: plugins/mutation-testing/skills/mutation-testing/SKILL.md
Commit: ad16332

Reviewed: 2 days ago

Table of Contents

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