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.
83
77%
Does it follow best practices?
Impact
87%
1.17xAverage score across 3 eval scenarios
Passed
No known issues
Optimize this skill with Tessl
npx tessl skill review --optimize ./.claude/skills/mutation-testing/SKILL.mdQuality
Discovery
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 specific capabilities could be more granular—listing concrete actions like analyzing surviving mutants, generating mutation reports, or suggesting test improvements would strengthen it further.
Suggestions
Add more specific concrete actions beyond the general 'evaluate' framing, such as 'analyze surviving mutants, generate mutation coverage reports, suggest test improvements to kill surviving mutants'.
| 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 targets. | 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', '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 mention of 'mutmut', 'mutation testing', and 'mutant detection' makes this highly distinct and unlikely to conflict with general testing or code quality skills. | 3 / 3 |
Total | 11 / 12 Passed |
Implementation
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 tests, executable commands, and practical CI integration. 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 the table is general knowledge.
Add an explicit iterative workflow with validation: run mutmut -> analyze survivors -> write targeted tests -> re-run on specific mutants -> verify mutation score improvement, with a clear checkpoint before declaring completion.
| Dimension | Reasoning | Score |
|---|---|---|
Conciseness | The 'Key Concepts' section explains mutation testing terminology that Claude likely already knows, and the 'Common Mutation Operators' table is general knowledge. However, the examples and configuration sections are reasonably efficient. The skill could be tightened by removing conceptual explanations. | 2 / 3 |
Actionability | The skill provides fully executable commands, complete configuration examples, runnable Python code with both weak and strong test examples, and a copy-paste ready CI workflow. All guidance is concrete and specific. | 3 / 3 |
Workflow Clarity | The Quick Start provides a clear sequence of commands, and the 'Improving Mutation Score' section gives a process. However, there's no explicit validation/feedback loop for the overall mutation testing workflow (e.g., run -> analyze survivors -> write tests -> re-run -> verify score improved). The process of iterating on survived mutants is implied but not explicitly sequenced with checkpoints. | 2 / 3 |
Progressive Disclosure | The content is reasonably well-structured with clear sections, but it's somewhat long for a single file with no references to supporting documents. The CI integration and common mutation operators table could be split into separate files. However, given no bundle files exist, the inline approach is acceptable though not ideal. | 2 / 3 |
Total | 9 / 12 Passed |
Validation
100%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
3ce3191
- Reviewed
Table of Contents
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