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atdd-mutate

Run mutation testing on ATDD two-stream test suites to measure kill and survive scores.

134|9|Updated Feb 16, 2026
Search Tags:#unit testing#test quality#mutation testing#ATDD#acceptance testing#differential testing#test gap analysis
One-click install
npx skills add https://github.com/swingerman/disciplined-agentic-engineering --skill atdd-mutate
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: atdd-mutate
Source: https://github.com/swingerman/disciplined-agentic-engineering/tree/main/skills/atdd-mutate
Command: npx skills add https://github.com/swingerman/disciplined-agentic-engineering --skill atdd-mutate

SYSTEM DOCUMENTATION & REQUIREMENTS

💡 This Skill includes references (resource) components.

What problem does it solve?

It helps you detect when an apparently “green” test suite is actually missing important behavioral checks by measuring whether tests fail when the code is intentionally broken.

Core Features & Use Cases

  • Mutation testing for ATDD: Extends the ATDD two-stream workflow (acceptance verifies WHAT, unit tests verify HOW) with a third validation layer that verifies the tests’ fault-detection strength.
  • Kill/survive analysis: Introduces targeted mutants and reports whether each mutant is killed (tests detect the bug) or survives (test gap).
  • Custom or framework execution: Supports a preferred project-specific custom mutation tool approach (AST/source-driven, targeted tests, cached differential runs) and a fallback to existing frameworks like Stryker, PIT, or mutmut.
  • Differential mutation testing: Reduces mutation run time by re-mutating only functions affected by code or covering-test changes via a committed mutation manifest or framework incremental modes.
  • Guardrails and anti-pattern prevention: Emphasizes mutating only source code (never acceptance/spec/generated artifacts) and only after both test streams are green.

Quick Start

Ask your AI agent: "Run mutation testing for my codebase using differential mutation testing and report the surviving mutants with suggested new unit tests to kill real test gaps."

Frequently Asked Questions about atdd-mutate

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How does mutation testing measure test gap analysis in an ATDD workflow?▼

Mutation testing measures test gaps by injecting targeted bugs into source code and reporting whether acceptance and unit tests fail to detect them. Surviving mutants indicate missing behavioral checks in an ATDD test suite.

Can I use Stryker or PIT for differential mutation testing on my codebase?▼

Yes, you can use existing frameworks like Stryker, PIT, or mutmut as a fallback for differential mutation testing. A preferred project-specific custom AST source-driven approach with cached differential runs is also supported.

How do I run mutation testing only on functions affected by recent code changes?▼

You can run differential mutation testing by re-mutating only functions affected by code or covering-test changes. This utilizes a committed mutation manifest or framework incremental modes to reduce overall mutation run time.

When should I run mutation testing in the ATDD two-stream workflow?▼

Mutation testing should run after both ATDD test streams are green. It serves as a third validation layer to verify the fault-detection strength of acceptance tests verifying WHAT and unit tests verifying HOW.

What code should be excluded from mutation testing to prevent anti-patterns?▼

Mutation testing must only mutate source code and never acceptance spec or generated pipeline artifacts. This guardrail prevents false positives and ensures tests are validated against actual implementation logic.

Why do my tests stay green when I introduce intentional bugs in my code?▼

Tests stay green because of test gaps where the suite lacks necessary behavioral checks. Mutation testing identifies these survivors by introducing targeted mutants and triaging which injected bugs go undetected.

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