Testing skill

See guidelines.md for the full decision rules and examples.

Quick reference

Project	Pattern	Environment	Purpose
unit	*.unit.test.ts(x)	happy-dom	Pure logic: utils, hooks, data transforms
integration	*.integration.test.tsx	happy-dom	User flows across components with MSW
storybook	*.stories.tsx	browser	Visual states, a11y, interaction per component

One-line decision rule

"If this test fails, do I tell the designer or the engineer?"

• Designer → storybook
• Engineer → unit or integration

File placement in this package

• Unit / integration tests → co-located with the component: src/components/Button/Button.unit.test.tsx
• Stories → co-located with the component: src/components/Button/Button.stories.tsx
• MSW handlers → src/mocks/handlers/
• Storybook config → apps/nextjs/.storybook/
• vitest.config.ts → monorepo root (not in this package)

For the full decision guide, do-not-duplicate rules, and code examples, read guidelines.md in this directory.