mezivillager/tdd

Test-Driven Development (TDD) for HACER

<instructions> You are an expert TDD practitioner. THE IRON LAW: NO PRODUCTION CODE WITHOUT A FAILING TEST FIRST. Write code before the test? Delete it. Start over.

Process: Red → Green → Refactor

RED — Write the failing test

Write one test that describes the behavior you want. Run it. Watch it fail. pnpm run test -- --run path/to/file.test.ts Confirm: The test fails (not errors out), it fails because the feature is missing, and the failure message is exactly what you expected.

GREEN — Write minimal code to pass

Write the smallest amount of production code that makes the test pass. No extra features. No refactoring. Just pass the test. pnpm run test -- --run path/to/file.test.ts

REFACTOR — Clean up while staying green

Remove duplication, improve names, extract helpers. Run tests after every change. Never add behavior during refactor.

Verification Checklist Before Marking Done

• [ ] Test written before implementation
• [ ] Watched test fail for the right reason
• [ ] Wrote minimal code to pass
• [ ] All tests pass: pnpm run test:run
• [ ] E2E store tests pass: pnpm run test:e2e:store
• [ ] No TypeScript errors: pnpm run lint </instructions>

<examples> <example> ### Pure logic (store actions, simulation) ```typescript import { describe, it, expect, beforeEach } from 'vitest' import { useCircuitStore, circuitActions } from '@/store/circuitStore'

beforeEach(() => { useCircuitStore.setState({ /* copy from canonical or derive from initialState */ }) })

it('should do X when Y', () => { circuitActions.someAction(/* args */) const state = useCircuitStore.getState() expect(state.someSlice).toBe(expected) })

</example>
<example>
### React components (React Testing Library)
```typescript
import { render, screen } from '@testing-library/react'
import { MyComponent } from './MyComponent'

it('renders label when visible', () => {
  render(<MyComponent visible={true} />)
  expect(screen.getByText('Expected Label')).toBeInTheDocument()
})

</example> </examples> <rules> ## HACER Test File Conventions - Store actions: `src/store/actions/myAction.test.ts` - React components: Co-located `src/components/MyComponent.test.tsx` - Generic logic: Co-located `src/utils/helpers.test.ts` - E2E Store tests: `e2e/specs/feature.spec.ts` (tagged `@store`)

Common Rationalizations to Reject

• "It's too simple to test" -> Simple code breaks. Test takes 30s.
• "I'll write tests after" -> Tests written after pass immediately, proving nothing.
• "I already manually tested it" -> Not systematic. Can't re-run in CI. </rules>