quality-assurance

Files (9)

• SKILL.md
• cross-browser-checklist.md · references/
• smoke.js · references/k6-load-test-templates/
• soak.js · references/k6-load-test-templates/
• spike.js · references/k6-load-test-templates/
• auth.spec.ts · references/playwright-setup-template/example-tests/
• navigation.spec.ts · references/playwright-setup-template/example-tests/
• playwright.config.ts · references/playwright-setup-template/
• testing-pyramid.md · references/

SKILL.md (first lines)

# Quality Assurance

You handle all testing strategy, test implementation, load testing, cross-browser validation, and code quality tooling. This skill covers the full testing pyramid from unit tests through production load testing.

## When this skill triggers

This skill activates when a developer asks about writing tests, setting up test infrastructure, improving code quality tooling, debugging flaky tests, load testing, or cross-browser compatibility.

---

## Testing Pyramid

Reference: `references/testing-pyramid.md`

Follow the testing pyramid to allocate effort correctly:

| Layer | Share | Speed | Tools | What to test |
|-------|-------|-------|-------|-------------|
| **Unit** | 70% | < 10ms each | Vitest | Pure functions, calculations, permissions, data transforms |
| **Integration** | 20% | < 2s each | Vitest + test DB | API routes, auth flows, DB queries, service interactions |
| **E2E** | 10% | < 30s each | Playwright | 4 critical user paths only |

<!-- beginner -->
**Why a pyramid?** Unit tests are fast and cheap. E2E tests are slow and brittle. If you write mostly E2E tests, your test suite takes 20 minutes and breaks constantly. The pyramid says: test most things at the unit level, some things with real integrations, and only the most critical user flows end-to-end.

<!-- intermediate -->
The pyramid is a cost model. Unit tests give the fastest feedback per dollar of maintenance. Integration tests catch wiring bugs that unit tests miss. E2E tests validate the 4 paths that would cost you customers if broken.

<!-- senior -->
70/20/10 split. Unit for logic, integration for wiring + DB, E2E for critical paths only. Track flake rate — kill any E2E test above 2%.

---

## Unit Tests

Reference: `references/testing-pyramid.md`

### Recommended stack

**Vitest** — drop-in replacement for Jest with native ESM, TypeScript, and Vite integration. Faster cold starts, native code coverage via v8.

### What to unit test

Focus 80% of unit test coverage on **business logic**, not UI:

| Test this | Skip this |
|-----------|-----------|
| Payment calculations | React component renders |
| Permission checks | CSS class assertions |
| Data transformations | Snapshot tests (fragile) |
| Validation logic | Third-party library wrappers |
| State machine transitions | Simple getters/setters |
| Date/currency formatting | Framework boilerplate |

### Copy-paste Vitest config

```ts
// vitest.config.ts
import { defineConfig } from 'vitest/config';
import path from 'path';

export default defineConfig({
  test: {
    globals: true,
    environment: 'node',
    include: ['src/**/*.test.ts', 'src/**/*.spec.ts'],
    exclude: ['src/**/*.e2e.ts', 'node_modules'],
    coverage: {
      provider: 'v8',
      reporter: ['text', 'lcov', 'html'],
      include: ['src/**/*.ts'],
      exclude: [
        'src/**/*.test.ts',
        'src/**/*.spec.ts',
        'src/**/*.d.ts',
        'src/**/types.ts',
        'src/**/index.ts',
      ],
      thresholds: {
        // [CUSTOMIZE] Adjust thresholds per your project maturity
        statements: 80,
        branches: 75,
        functions: 80,
        lines: 80,
      },
    },
    setupFiles: ['./src/test/setup.ts'],
  },
  resolve: {
    alias: {
      '@': path.resolve(__dirname, './src'),
    },
  },
});
```

### Example unit test

```ts
// src/features/billing/utils/calculate-invoice.test.ts
import { describe, it, expect } from 'vitest';
import { calculateInvoiceTotal } from './calculate-invoice';

describe('calculateInvoiceTotal', () => {
  it('sums line items correctly', () => {
    const items = [
      { quantity: 2, unitPrice: 10.0 },
      { quantity: 1, unitPrice: 25.5 },
    ];
    expect(calculateInvoiceTotal(items)).toBe(45.5);
  });

  it('applies percentage discount', () => {
    const items = [{ quantity: 1, unitPrice: 100 }];
    expect(calculateInvoiceTotal(items, { discountPercent: 20 })).toBe(80);
  });

  it('returns 0 for empty items', () => {
    expect(calculateInvoiceTotal([])).toBe(0);

From harmansidhudev/shipwise, MIT.

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