mutation-testing

Evaluate Python test suite quality using mutmut to introduce code mutations and verify tests catch them. Use for mutation testing, test quality assessment, mutant detection, and test effectiveness analysis.

1.17x

Quality

77%

Does it follow best practices?

Impact

87%

1.17x

Average score across 3 eval scenarios

Securityby

Passed

No known issues

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

Quality

Content

64%

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

This is a solid, actionable skill with excellent concrete examples showing weak vs strong test patterns and ready-to-use commands and configurations. Its main weaknesses are some unnecessary conceptual explanation (key concepts, mutation operators table) that Claude already knows, and a lack of an explicit iterative workflow with validation checkpoints for the mutation testing cycle.

Suggestions

Remove or significantly trim the 'Key Concepts' section and 'Common Mutation Operators' table — Claude already understands these concepts and mutmut documents them.

Add an explicit iterative workflow: run mutmut → identify survived mutants → write targeted tests → re-run mutmut to confirm kills → repeat until target score reached.

Consider splitting CI integration and the mutation operators reference into separate bundle files to keep the main skill lean.

Dimension	Reasoning	Score
Conciseness	The key concepts section explains mutation testing basics that Claude likely already knows. The common mutation operators table and best practices section add some bulk. However, the examples and code blocks are reasonably tight and informative.	2 / 3
Actionability	Provides fully executable commands (pip install, mutmut run, etc.), complete configuration examples, executable Python test code showing weak vs strong patterns, and a ready-to-use CI workflow YAML. All code is copy-paste ready.	3 / 3
Workflow Clarity	The quick start commands are sequenced but there's no explicit validation/feedback loop for the mutation testing workflow itself. When mutants survive, the guidance is general ('add tests for...') rather than a clear iterative process with checkpoints like 'run mutmut again to verify the mutant is now killed.'	2 / 3
Progressive Disclosure	The content is well-structured with clear headers, but it's a fairly long monolithic file (~130 lines of content). The CI integration and common mutation operators table could be split into separate reference files. No bundle files exist to offload detail.	2 / 3
	Total	9 / 12 Passed

Description

89%

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

This is a solid skill description that clearly identifies its niche (mutation testing with mutmut for Python), provides explicit trigger guidance, and is highly distinctive. The main weakness is that the specificity of concrete actions could be improved by listing more granular capabilities beyond the high-level 'introduce mutations and verify tests catch them'.

Suggestions

Add more specific concrete actions such as 'analyze surviving mutants', 'generate mutation coverage reports', or 'identify weak test cases' to improve specificity.

Dimension	Reasoning	Score
Specificity	Names the domain (mutation testing with mutmut) and the core action (introduce code mutations and verify tests catch them), but doesn't list multiple specific concrete actions like generating reports, analyzing surviving mutants, or configuring mutation operators.	2 / 3
Completeness	Clearly answers both 'what' (evaluate Python test suite quality using mutmut to introduce code mutations and verify tests catch them) and 'when' ('Use for mutation testing, test quality assessment, mutant detection, and test effectiveness analysis').	3 / 3
Trigger Term Quality	Includes strong natural trigger terms: 'mutation testing', 'test quality', 'mutant detection', 'test effectiveness', 'mutmut', and 'Python test suite'. These cover the natural ways a user would phrase requests in this domain.	3 / 3
Distinctiveness Conflict Risk	Mutation testing with mutmut is a very specific niche. The combination of 'mutmut', 'mutation testing', and 'mutant detection' makes this highly distinctive and unlikely to conflict with general testing or code quality skills.	3 / 3
	Total	11 / 12 Passed

Validation

100%

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 — 11 / 11 Passed

Validation for skill structure

No warnings or errors.

Repository: mixpanel/mixpanel-headless
Commit: fd7b9ba

Reviewed: 26 days ago

Table of Contents

Discovery Implementation Validation

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