@a11ycore/jest

Custom Jest matcher for aXe for testing accessibility

⚠️✋ This project does not guarantee what you build is accessible.

The GDS Accessibility team found that only ~30% of issues are found by automated testing.

Installation:

npm install --save-dev @a11ycore/jest

Usage:

const React = require("react");
const ReactDOMServer = require("react-dom/server");
const { runA11yJest } = require("@a11ycore/jest");

describe("jest", () => {
  test("it should call the runA11yMethod", async () => {
    const element = React.createElement("img", { src: "#" });
    const html = ReactDOMServer.renderToString(element);
    const results = await runA11yJest(html)
    expect(results.violations.length).toBeGreaterThan(1);
  });
});

Testing React with Enzyme

const React = require('react')
const App = require('./app')

const { mount } = require('enzyme')
const { runA11yJest } = require('@a11ycore/jest')

it('should demonstrate this matcher`s usage with enzyme', async () => {
  const wrapper = mount(<App/>)
  const results = await runA11yJest(wrapper.getDOMNode())
  expect(results.violations.length).toBe(0);
})

Testing React with React Testing Library

const React = require('react')
const App = require('./app')

const { render } = require('@testing-library/react')
const { runA11yJest } = require('@a11ycore/jest')

it('should demonstrate this matcher`s usage with react testing library', async () => {
  const { container } = render(<App/>)
  const results = await runA11yJest(container)
  expect(results.violations.length).toBe(0);
})

Note: If you're using react testing library <9.0.0 you should be using the cleanup method. This method removes the rendered application from the DOM and ensures a clean HTML Document for further testing.

Testing Vue with Vue Test Utils

const App = require('./App.vue')

const { mount } = require('@vue/test-utils')
const { runA11yJest } = require('@a11ycore/jest')

it('should demonstrate this matcher`s usage with vue test utils', async () => {
  const wrapper = mount(Image)
  const results = await runA11yJest(wrapper.element)
  expect(results.violations.length).toBe(0);
})

Testing Vue with Vue Testing Library

const App = require('./app')

const { render } = require('@testing-library/vue')
const { runA11yJest } = require('@a11ycore/jest')

it('should demonstrate this matcher`s usage with react testing library', async () => {
  const { container } = render(<App/>)
  const results = await runA11yJest(container)
  
  expect(results.violations.length).toBe(0);
})

Note: If you're using vue testing library <3.0.0 you should be using the cleanup method. This method removes the rendered application from the DOM and ensures a clean HTML Document for further testing.

configureA11yJest configuration

The runA11yJest function allows options to be set with the same options as documented in axe-core:

const { runA11yJest } = require('@a11ycore/jest')

it('should demonstrate this matcher`s usage with a custom config', async () => {
  const render = () => `
    <div>
      <img src="#"/>
    </div>
  `

  // pass anything that outputs html to axe
  const html = render()

  const results = await runA11yJest(html, {
    rules: {
      // for demonstration only, don't disable rules that need fixing.
      'image-alt': { enabled: false }
    }
  })

  expect(results.violations.length).toBe(0);
})

Setting global configuration

If you find yourself repeating the same options multiple times, you can export a version of the runA11yJest function with defaults set.

Note: You can still pass additional options to this new instance; they will be merged with the defaults.

This could be done in Jest's setup step

// Global helper file (axe-helper.js)
const { configureA11yJest } = require('@a11ycore/jest')

const runA11yJest = configureA11yJest({
  rules: {
    // for demonstration only, don't disable rules that need fixing.
    'image-alt': { enabled: false }
  }
})

module.exports = runA11yJest

Setting custom rules and checks.

The configuration object passed to configureA11yJest, accepts a globalOptions property to configure the format of the data used by axe and to add custom checks and rules. The property value is the same as the parameter passed to axe.configure.

// Global helper file (axe-helper.js)
const { configureA11yJest } = require('@a11ycore/jest')

const runA11yCore = configureA11yJest({
  globalOptions: {
    checks: [/* custom checks definitions */]
  },
  // ...
})

module.exports = runA11yCore

Refer to Developing Axe-core Rules for instructions on how to develop custom rules and checks.

Thanks

• Jest for the great test runner that allows extending matchers.
• aXe for the wonderful axe-core that makes it so easy to do this.
• Government Digital Service for making coding in the open the default.
  • GOV.UK Publishing Frontend team who published the basis of the aXe reporter
• jest-image-snapshot for inspiration on README and repo setup