quality

# Quality Engineering

Ship reliable, accessible, performant software.

## Quick Reference

### Testing Stack (2026)

| Type        | Tool               | Purpose               |
| ----------- | ------------------ | --------------------- |
| Unit        | Vitest             | Fast, Vite-native     |
| Component   | Testing Library    | User-centric          |
| E2E         | Playwright         | Cross-browser         |
| API         | Playwright API     | Request testing       |
| Visual      | Playwright + Percy | Screenshot comparison |
| A11y        | Axe-core           | WCAG compliance       |
| Performance | Lighthouse CI      | Core Web Vitals       |

### Vitest Setup

```typescript
// vitest.config.ts
import { defineConfig } from "vitest/config";

export default defineConfig({
  test: {
    globals: true,
    environment: "jsdom",
    setupFiles: ["./tests/setup.ts"],
    coverage: {
      provider: "v8",
      reporter: ["text", "json", "html"],
      exclude: ["node_modules", "tests"],
    },
  },
});
```

**Writing Tests:**

```typescript
import { describe, it, expect, vi } from 'vitest';
import { render, screen } from '@testing-library/react';
import { UserProfile } from './UserProfile';

describe('UserProfile', () => {
  it('displays user name', () => {
    render(<UserProfile user={{ name: 'Alice' }} />);
    expect(screen.getByText('Alice')).toBeInTheDocument();
  });

  it('calls onEdit when button clicked', async () => {
    const onEdit = vi.fn();
    render(<UserProfile user={{ name: 'Alice' }} onEdit={onEdit} />);
    await userEvent.click(screen.getByRole('button', { name: /edit/i }));
    expect(onEdit).toHaveBeenCalledTimes(1);
  });
});
```

### Playwright E2E

```typescript
// tests/auth.spec.ts
import { test, expect } from "@playwright/test";

test.describe("Authentication", () => {
  test("user can log in", async ({ page }) => {
    await page.goto("/login");
    await page.getByLabel("Email").fill("user@example.com");
    await page.getB