| name | ae-ltd-mutation-gate |
| description | Use when unit tests look green but confidence is low and mutation testing is needed to expose weak assertions. AE.LTD workflow for targeted mutation runs and actionable test hardening. |
AE.LTD Mutation Gate
What This Skill Does
Measures test quality beyond line coverage using mutation testing. Exposes weak assertions and generates actionable test hardening recommendations. Niche gem source: mutation-tester plugin from awesome-claude-code-toolkit.
- Detect appropriate mutation tool (Stryker/mutmut/PIT)
- Run targeted mutation tests on critical modules
- Convert survived mutants into hardened tests
- Track mutation score to threshold (target: 80%+)
Quick Start
User: "My tests pass but I'm not confident"
→ Detect stack → Run mutations → Report survivors → Harden tests
Workflow
- Detect stack and tool.
- JS/TS: Stryker
- Python: mutmut
- Java: PIT
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Start narrow.
Run mutation testing on one critical module first to keep runtime bounded.
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Measure score and survivors.
Capture killed/survived/timed-out mutants and mutation score.
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Convert survivors into tests.
For each top survived mutant, specify the exact missing assertion and test case.
-
Re-run until stable threshold.
Target at least 80% mutation score unless user/project standard says otherwise.
Guardrails
- Exclude generated files and non-business logic.
- Use per-mutant timeouts to control runaway test runs.
- Report equivalent-mutant risk explicitly.
- Prioritize critical-path business logic over utility files.
