atdd-mutate

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."