axe-core - Quick Reference

When NOT to Use This Skill

• Manual WCAG compliance audits - Use the wcag skill for understanding guidelines and manual testing
• Screen reader testing - axe-core doesn't replace manual screen reader verification
• Complex ARIA pattern implementation - Use wcag skill for ARIA authoring practices
• Accessibility strategy planning - This is for test automation, not accessibility consulting

Deep Knowledge: Use mcp__documentation__fetch_docs with technology: axe-core for comprehensive documentation on rules, configuration, and integrations.

Setup Base

npm install -D @axe-core/react  # For React
npm install -D axe-core         # Core library

Pattern Essenziali

React DevTools Integration

import React from 'react';
import ReactDOM from 'react-dom/client';

if (process.env.NODE_ENV !== 'production') {
  import('@axe-core/react').then(axe => {
    axe.default(React, ReactDOM, 1000);
  });
}

Jest/Vitest Integration

import { axe, toHaveNoViolations } from 'jest-axe';

expect.extend(toHaveNoViolations);

test('should have no accessibility violations', async () => {
  const { container } = render(<MyComponent />);
  const results = await axe(container);
  expect(results).toHaveNoViolations();
});

Playwright Integration

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

test('should not have accessibility issues', async ({ page }) => {
  await page.goto('/');

  const accessibilityScanResults = await new AxeBuilder({ page }).analyze();

  expect(accessibilityScanResults.violations).toEqual([]);
});

// With specific rules
test('should pass WCAG AA', async ({ page }) => {
  await page.goto('/');

  const results = await new AxeBuilder({ page })
    .withTags(['wcag2a', 'wcag2aa'])
    .analyze();

  expect(results.violations).toEqual([]);
});

Cypress Integration

// cypress/support/commands.ts
import 'cypress-axe';

// In test
describe('Accessibility', () => {
  it('has no violations', () => {
    cy.visit('/');
    cy.injectAxe();
    cy.checkA11y();
  });
});

Programmatic Usage

import axe from 'axe-core';

async function checkAccessibility() {
  const results = await axe.run();

  if (results.violations.length > 0) {
    console.log('Violations:', results.violations);
  }
}

Anti-Patterns

| Anti-Pattern | Why It's Wrong | Correct Approach | |-------------|----------------|------------------| | Running axe on empty/loading states | Tests incomplete DOM, false negatives | Wait for content to load before running axe | | Ignoring all violations | Defeats purpose of automated testing | Fix violations or document exceptions with reasoning | | Testing only homepage | Most accessibility issues in complex interactions | Test all critical user flows and components | | Not configuring WCAG level | Tests against all rules, may be too strict | Set withTags(['wcag2a', 'wcag2aa']) for target level | | Running axe synchronously in loops | Slow test execution | Use Promise.all() for parallel execution | | Committing violations to CI | Prevents catching regressions | Fail builds on new violations | | Testing hidden/inactive components | Axe tests invisible elements unnecessarily | Use exclude parameter for hidden sections | | No baseline for legacy code | All violations block progress | Create baseline, track improvements incrementally |

Quick Troubleshooting

| Issue | Diagnosis | Solution | |-------|-----------|----------| | axe finds no violations but page is inaccessible | Automated tools catch only ~30-40% of issues | Supplement with manual keyboard and screen reader testing | | "No violations" but form has issues | axe doesn't test form logic/flow | Test form submission, error handling manually | | Timeout in Playwright axe tests | Large/complex page takes too long | Increase timeout or analyze specific regions | | False positive on custom component | axe rule doesn't understand pattern | Use disableRules or add proper ARIA to fix | | Violations in third-party widgets | Can't modify external code | Document exceptions, contact vendor, or replace widget | | Different results in different browsers | Browser-specific rendering differences | Run axe in multiple browsers, use cross-browser test suite | | CI fails but local passes | Environment differences (timing, content) | Ensure consistent test data and wait conditions | | Too many violations to fix at once | Legacy codebase with extensive issues | Create baseline, use --save flag to track improvements |