ae-ltd-mutation-gate

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.

1. Detect appropriate mutation tool (Stryker/mutmut/PIT)
2. Run targeted mutation tests on critical modules
3. Convert survived mutants into hardened tests
4. 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

1. Detect stack and tool.

• JS/TS: Stryker
• Python: mutmut
• Java: PIT

2. Start narrow. Run mutation testing on one critical module first to keep runtime bounded.

3. Measure score and survivors. Capture killed/survived/timed-out mutants and mutation score.

4. Convert survivors into tests. For each top survived mutant, specify the exact missing assertion and test case.

5. 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.