Axe-Playwright

Axe is an accessibility testing engine for websites and other HTML-based user interfaces. This package provides simple axe analyser commands which you can incorporate in your Playwright tests.The idea is highly inspired by Andy Van Slaars cypress-axe project.

Install and configure

Add as a dev dependency:

npm i -D axe-playwright

Install peer dependencies:

npm i -D playwright

NOTE: axe-core is now bundled and doesn't need to be installed as a peer dependency

Add Typings

//tsconfig.json
{
  "compilerOptions": {
    "types": ["axe-playwright"]
  }
}

Commands

injectAxe

This will inject the axe-core runtime into the page under test. You must run this after a call to page.goto() and before you run the checkA11y command.

You run this command with injectAxe() either in your test, or in a beforeEach, as long as the visit comes first.

beforeAll(async () => {
  browser = await chromium.launch()
  page = await browser.newPage()
  await page.goto(`http://localhost:3000/login`)
  await injectAxe(page)
})

configureAxe

Purpose

To configure the format of the data used by aXe. This can be used to add new rules, which must be registered with the library to execute.

Description

User specifies the format of the JSON structure passed to the callback of axe.run

Link - aXe Docs: axe.configure

it('Has no detectable a11y violations on load (custom configuration)', async () => {
  // Configure aXe and test the page at initial load
  await configureAxe(page, {
    branding: {
      brand: String,
      application: String,
    },
    reporter: 'option',
    checks: [Object],
    rules: [Object],
    locale: Object,
  })
  await checkA11y()
})

checkA11y

This will run axe against the document at the point in which it is called. This means you can call this after interacting with your page and uncover accessibility issues introduced as a result of rendering in response to user actions.

Parameters on checkA11y (axe.run)

page (mandatory)

The page instance of playwright.

context (optional)

Defines the scope of the analysis - the part of the DOM that you would like to analyze. This will typically be the document or a specific selector such as class name, ID, selector, etc.

options (optional)

Set of options passed into rules or checks, temporarily modifying them. This contrasts with axe.configure, which is more permanent.

The keys consist of those accepted by axe.run's options argument as well as custom includedImpacts, detailedReport, and detailedReportOptions keys.

The includedImpacts key is an array of strings that map to impact levels in violations. Specifying this array will only include violations where the impact matches one of the included values. Possible impact values are "minor", "moderate", "serious", or "critical".

Filtering based on impact in combination with the skipFailures argument allows you to introduce axe-playwright into tests for a legacy application without failing in CI before you have an opportunity to address accessibility issues. Ideally, you would steadily move towards stricter testing as you address issues. e-effects, such as adding custom output to the terminal.

NOTE: This respects the includedImpacts filter and will only execute with violations that are included.

The detailedReport key is a boolean whether to print the more detailed report detailedReportOptions is an object with the shape

{
 html?: boolean // include the full html for the offending nodes
}

reporter (optional)

A class instance that implements the Reporter interface. Custom reporter instances can be supplied to override default reporting behaviour dictated by DefaultTerminalReporter.

skipFailures (optional, defaults to false)

Disables assertions based on violations and only logs violations to the console output. If you set skipFailures as true, although accessibility check is not passed, your test will not fail. It will simply print the violations in the console, but will not make the test fail.

getViolations

This will run axe against the document at the point in which it is called, then return you an array of accessibility violations.

Parameters on getViolations (axe.run)

page (mandatory)

The page instance of playwright.

context (optional)

Defines the scope of the analysis - the part of the DOM that you would like to analyze. This will typically be the document or a specific selector such as class name, ID, selector, etc.

options (optional)

Set of options passed into rules or checks, temporarily modifying them. This contrasts with axe.configure, which is more permanent.

The keys consist of those accepted by axe.run's options argument as well as custom includedImpacts, detailedReport, and detailedReportOptions keys.

The includedImpacts key is an array of strings that map to impact levels in violations. Specifying this array will only include violations where the impact matches one of the included values. Possible impact values are "minor", "moderate", "serious", or "critical".

Filtering based on impact in combination with the skipFailures argument allows you to introduce axe-playwright into tests for a legacy application without failing in CI before you have an opportunity to address accessibility issues. Ideally, you would steadily move towards stricter testing as you address issues. e-effects, such as adding custom output to the terminal.

NOTE: This respects the includedImpacts filter and will only execute with violations that are included.

The detailedReport key is a boolean whether to print the more detailed report detailedReportOptions is an object with the shape

{
 html?: boolean // include the full html for the offending nodes
}

reportViolations

Reports violations based on the Reporter concrete implementation behaviour.

Parameters on reportViolations

violations (mandatory)

An array of Axe violations to be printed.

reporter (mandatory)

A class instance that implements the Reporter interface. Custom reporter instances can be supplied to override default reporting behaviour dictated by DefaultTerminalReporter.

Examples

Basic usage

import { chromium, Browser, Page } from 'playwright'
import { injectAxe, checkA11y, getViolations, reportViolations } from 'axe-playwright'

let browser: Browser
let page: Page

describe('Playwright web page accessibility test', () => {
  beforeAll(async () => {
    browser = await chromium.launch()
    page = await browser.newPage()
    await page.goto(`file://${process.cwd()}/test/site.html`)
    await injectAxe(page)
  })

  it('simple accessibility run', async () => {
    await checkA11y(page)
  })

  it('check a11y for the whole page and axe run options', async () => {
    await checkA11y(page, null, {
      axeOptions: {
        runOnly: {
          type: 'tag',
          values: ['wcag2a'],
        },
      },
    })
  })

  it('check a11y for the specific element', async () => {
    await checkA11y(page, 'input[name="password"]', {
      axeOptions: {
        runOnly: {
          type: 'tag',
          values: ['wcag2a'],
        },
      },
    })
  })

  it('gets and reports a11y for the specific element', async () => {
    const violations = await getViolations(page, 'input[name="password"]', {
      axeOptions: {
        runOnly: {
          type: 'tag',
          values: ['wcag2a'],
        },
      },
    })

    reportViolations(violations, new YourAwesomeCsvReporter('accessibility-report.csv'))

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

  afterAll(async () => {
    await browser.close()
  })
})

This custom logging behavior results in terminal output like this:

Detailed Report

The detailed report is disabled by default, but can be enabled by including the detailedReport property in the checkAlly options.

import { chromium, Browser, Page } from 'playwright'
import { injectAxe, checkA11y } from 'axe-playwright'

let browser: Browser
let page: Page

describe('Playwright web page accessibility test', () => {
  beforeAll(async () => {
    browser = await chromium.launch()
    page = await browser.newPage()
    await page.goto(`file://${process.cwd()}/test/site.html`)
    await injectAxe(page)
  })

  // Prints outs a detailed report per node with an array of numbers of which violations from the summary affect that node
  it('print out a detailed report on violations', async () => {
    await checkA11y(page, null, {
      detailedReport: true,
    })
  })

  // Same as above, but includes the html of the offending node
  it('print out a detailed report on violations', async () => {
    await checkA11y(page, null, {
      detailedReport: true,
      detailedReportOptions: { html: true },
    })
  })

  afterAll(async () => {
    await browser.close()
  })
})

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