Superpowers Whetstone Plugin
Collection of testing skills for behavior-first development with Outside-In TDD, Gherkin, and mutation testing.
What's Included
Skills
- gherkin-gate - Capture observable behavior in business language and require user approval before writing tests or implementation.
- red-synthesize-green - Enforce the 2-step AI TDD cycle: write a failing test with stubs only, validate the red state with a human, then synthesize the real implementation.
- outside-in-tdd - Drive implementation from approved scenarios, start from observable behavior, and let domain design emerge from failing tests.
- mutation-testing - Verify that your test suite actually detects regressions once the baseline is green.
Migration Note
- Testing guidance that used to live in
application-layer-testingis now part of theoutside-in-tddskill in this plugin.
Installation
Install this plugin via Copilot CLI:
copilot plugin install superpowers-whetstone
Or clone the repository and reference locally.
What You'll Learn
This plugin provides practical guidance on:
- Describing behavior with Gherkin before implementation
- Translating business scenarios into acceptance-style tests
- Letting domain objects emerge from red instead of designing them upfront
- Using real domain objects and mocking only external boundaries
- Running mutation testing after the test baseline is green
Quick Start
- Start with
gherkin-gateto write and validate business scenarios. - Use
red-synthesize-greento enforce the AI TDD cycle: write a failing test with stubs, validate the red state, then synthesize implementation. - Continue with
outside-in-tddto turn approved scenarios into tests and implementation. - Finish with
mutation-testingto validate test effectiveness before merge.
Best Fit
Use this plugin when you want to:
- Practice behavior-first development
- Work with DDD and Clean Architecture in a test-first workflow
- Improve confidence in test quality beyond code coverage
Contributing
See main repository CONTRIBUTING.md for guidelines.