a11y-playwright-testing

分类: 开发与编程 | 上传者: fugazi | 下载: 0 | 版本: v1.0（最新）
Accessibility testing for web applications using Playwright (@playwright/test) with TypeScript and axe-core. Use when asked to write, run, or debug automated accessibility checks, keyboard navigation tests, focus management, ARIA/semantic validations, screen reader compatibility, or WCAG 2.1 Level AA compliance testing. Covers axe-core integration, POUR principles (perceivable, operable, understandable, robust), color contrast, form labels, landmarks, and accessible names.
更新日志: Source: GitHub https://github.com/fugazi/test-automation-skills-agents
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当前层级: skills/a11y-playwright-testing/
📁 references/
- 📄 aria_patterns.md 15.1 KB
- 📄 snippets.md 16.5 KB
- 📄 wcag21aa-checklist.md 5.3 KB
📄 SKILL.md 9.6 KB
SKILL.md

---
name: a11y-playwright-testing
description: Accessibility testing for web applications using Playwright (@playwright/test) with TypeScript and axe-core. Use when asked to write, run, or debug automated accessibility checks, keyboard navigation tests, focus management, ARIA/semantic validations, screen reader compatibility, or WCAG 2.1 Level AA compliance testing. Covers axe-core integration, POUR principles (perceivable, operable, understandable, robust), color contrast, form labels, landmarks, and accessible names.
---

# Playwright Accessibility Testing (TypeScript)

Comprehensive toolkit for automated accessibility testing using Playwright with TypeScript and axe-core. Enables WCAG 2.1 Level AA compliance verification, keyboard operability testing, semantic validation, and accessibility regression prevention.

> **Activation:** This skill is triggered when working with accessibility testing, WCAG compliance, axe-core scans, keyboard navigation tests, focus management, ARIA validation, or screen reader compatibility.

## When to Use This Skill

- **Automated a11y scans** with axe-core for WCAG 2.1 AA compliance
- **Keyboard navigation tests** for Tab/Enter/Space/Escape/Arrow key operability
- **Focus management** validation for dialogs, menus, and dynamic content
- **Semantic structure** assertions for landmarks, headings, and ARIA
- **Form accessibility** testing for labels, errors, and instructions
- **Color contrast** and visual accessibility verification
- **Screen reader** compatibility testing patterns

## Prerequisites

| Requirement | Details |
|-------------|---------|
| Node.js | v18+ recommended |
| Playwright | `@playwright/test` installed |
| axe-core | `@axe-core/playwright` package |
| TypeScript | Configured in project |

### Quick Setup

```bash
# Add axe-core to existing Playwright project
npm install -D @axe-core/playwright axe-core
```

## First Questions to Ask

Before writing accessibility tests, clarify:

1. **Scope**: Which pages/flows are in scope? What's explicitly excluded?
2. **Standard**: WCAG 2.1 AA (default) or specific organizational policy?
3. **Priority**: Which components are highest risk (forms, modals, navigation, checkout)?
4. **Exceptions**: Known constraints (legacy markup, third-party widgets)?
5. **Assistive Tech**: Which screen readers/browsers need manual testing?

---

## Core Principles

### 1. Automation Limitations

> ⚠️ **Critical**: Automated tooling can detect ~30-40% of accessibility issues. Use automation to prevent regressions and catch common failures; **manual audits are required** for full WCAG conformance.

### 2. Semantic HTML First

Prefer native HTML semantics over ARIA. Use ARIA only when native elements cannot achieve the required semantics.

```typescript
// ✅ Semantic HTML - inherently accessible
await page.getByRole('button', { name: 'Submit' }).click();

// ❌ ARIA override - requires manual keyboard/focus handling
await page.locator('[role="button"]').click(); // Often a <div>
```

### 3. Locator Strategy as A11y Signal

If you **cannot locate an element by role or label**, it's often an accessibility defect.

| Locator Success | Accessibility Signal |
|-----------------|---------------------|
| `getByRole('button', { name: 'Submit' })` ✅ | Button has accessible name |
| `getByLabel('Email')` ✅ | Input properly labeled |
| `getByRole('navigation')` ✅ | Landmark exists |
| `locator('.submit-btn')` ⚠️ | May lack accessible name |

---

## Key Workflows

### Automated Axe Scan (WCAG 2.1 AA)

```typescript
import AxeBuilder from '@axe-core/playwright';
import { test, expect } from '@playwright/test';

test('page has no WCAG 2.1 AA violations', async ({ page }) => {
  await page.goto('/');
  
  const results = await new AxeBuilder({ page })
    .withTags(['wcag2a', 'wcag2aa', 'wcag21a', 'wcag21aa'])
    .analyze();
  
  expect(results.violations).toEqual([]);
});
```

### Scoped Axe Scan (Component-Level)

```typescript
test('form component is accessible', async ({ page }) => {
  await page.goto('/contact');
  
  const results = await new AxeBuilder({ page })
    .include('#contact-form') // Scope to specific component
    .withTags(['wcag2a', 'wcag2aa', 'wcag21a', 'wcag21aa'])
    .analyze();
  
  expect(results.violations).toEqual([]);
});
```

### Keyboard Navigation Test

```typescript
test('form is keyboard navigable', async ({ page }) => {
  await page.goto('/login');
  
  // Tab to first field
  await page.keyboard.press('Tab');
  await expect(page.getByLabel('Email')).toBeFocused();
  
  // Tab to password
  await page.keyboard.press('Tab');
  await expect(page.getByLabel('Password')).toBeFocused();
  
  // Tab to submit button
  await page.keyboard.press('Tab');
  await expect(page.getByRole('button', { name: 'Sign in' })).toBeFocused();
  
  // Submit with Enter
  await page.keyboard.press('Enter');
  await expect(page).toHaveURL(/dashboard/);
});
```

### Dialog Focus Management

```typescript
test('dialog traps and returns focus', async ({ page }) => {
  await page.goto('/settings');
  const trigger = page.getByRole('button', { name: 'Delete account' });
  
  // Open dialog
  await trigger.click();
  const dialog = page.getByRole('dialog');
  await expect(dialog).toBeVisible();
  
  // Focus should be inside dialog
  await expect(dialog.getByRole('button', { name: 'Cancel' })).toBeFocused();
  
  // Tab should stay trapped in dialog
  await page.keyboard.press('Tab');
  await expect(dialog.getByRole('button', { name: 'Confirm' })).toBeFocused();
  await page.keyboard.press('Tab');
  await expect(dialog.getByRole('button', { name: 'Cancel' })).toBeFocused();
  
  // Escape closes and returns focus to trigger
  await page.keyboard.press('Escape');
  await expect(dialog).toBeHidden();
  await expect(trigger).toBeFocused();
});
```

### Skip Link Validation

```typescript
test('skip link moves focus to main content', async ({ page }) => {
  await page.goto('/');
  
  // First Tab should focus skip link
  await page.keyboard.press('Tab');
  const skipLink = page.getByRole('link', { name: /skip to (main|content)/i });
  await expect(skipLink).toBeFocused();
  
  // Activating skip link moves focus to main
  await page.keyboard.press('Enter');
  await expect(page.locator('#main, [role="main"]').first()).toBeFocused();
});
```

---

## POUR Principles Reference

| Principle | Focus Areas | Example Tests |
|-----------|-------------|---------------|
| **Perceivable** | Alt text, captions, contrast, structure | Image alternatives, color contrast ratio |
| **Operable** | Keyboard, focus, timing, navigation | Tab order, focus visibility, skip links |
| **Understandable** | Labels, instructions, errors, consistency | Form labels, error messages, predictable behavior |
| **Robust** | Valid HTML, ARIA, name/role/value | Semantic structure, accessible names |

---

## Axe-Core Tags Reference

| Tag | WCAG Level | Use Case |
|-----|------------|----------|
| `wcag2a` | Level A | Minimum compliance |
| `wcag2aa` | Level AA | **Standard target** |
| `wcag2aaa` | Level AAA | Enhanced (rarely full) |
| `wcag21a` | 2.1 Level A | WCAG 2.1 specific A |
| `wcag21aa` | 2.1 Level AA | **WCAG 2.1 standard** |
| `best-practice` | Beyond WCAG | Additional recommendations |

### Default Tags (WCAG 2.1 AA)

```typescript
const WCAG21AA_TAGS = ['wcag2a', 'wcag2aa', 'wcag21a', 'wcag21aa'];
```

---

## Exception Handling

When exceptions are unavoidable:

1. **Scope narrowly** - specific component/route only
2. **Document impact** - which WCAG criterion, user impact
3. **Set expiration** - owner + remediation date
4. **Track ticket** - link to remediation issue

```typescript
// ❌ Avoid: Global rule disable
new AxeBuilder({ page }).disableRules(['color-contrast']);

// ✅ Better: Scoped exclusion with documentation
new AxeBuilder({ page })
  .exclude('#third-party-widget') // Known issue: JIRA-1234, fix by Q2
  .withTags(['wcag2a', 'wcag2aa', 'wcag21a', 'wcag21aa'])
  .analyze();
```

---

## Troubleshooting

| Problem | Cause | Solution |
|---------|-------|----------|
| Axe finds 0 violations but app fails manual audit | Automation covers ~30-40% | Add manual testing checklist |
| False positive on dynamic content | Content not fully rendered | Wait for stable state before scan |
| Color contrast fails incorrectly | Background image/gradient | Use `exclude` for known false positives |
| Cannot find element by role | Missing semantic HTML | Fix markup - this is a real bug |
| Focus not visible | Missing `:focus` styles | Add visible focus indicator CSS |
| Dialog focus not trapped | Missing focus trap logic | Implement focus trap (see snippets) |
| Skip link doesn't work | Target missing `tabindex="-1"` | Add tabindex to main content |

---

## CLI Quick Reference

| Command | Description |
|---------|-------------|
| `npx playwright test --grep "a11y"` | Run accessibility tests only |
| `npx playwright test --headed` | Run with visible browser for debugging |
| `npx playwright test --debug` | Step through with Inspector |
| `PWDEBUG=1 npx playwright test` | Debug mode with pause |

---

## References

| Document | Content |
|----------|---------|
| [Snippets](./references/snippets.md) | axe-core setup, helpers, keyboard/focus patterns |
| [WCAG 2.1 AA Checklist](./references/wcag21aa-checklist.md) | Manual audit checklist by POUR principle |
| [ARIA Patterns](./references/aria_patterns.md) | Common ARIA widget patterns and validations |

## External Resources

| Resource | URL |
|----------|-----|
| WCAG 2.1 Specification | https://www.w3.org/TR/WCAG21/ |
| WCAG Quick Reference | https://www.w3.org/WAI/WCAG21/quickref/ |
| WAI-ARIA Authoring Practices | https://www.w3.org/WAI/ARIA/apg/ |
| axe-core Rules | https://dequeuniversity.com/rules/axe/ |
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a11y-playwright-testing

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