Writing Tests for Axe DevTools for Web for Puppeteer

Writing tests with Axe DevTools

Producing accessibility scan results with Axe DevTools can be as easy as one line of code. These results can be consumed raw, used in conjunction with an assertion library, or used to create accessibility reports.

The individual snippets in the sections below are JavaScript, and they compile unchanged in TypeScript. The Complete Sample File section gives the full test in both languages.

Prerequisites

In order to import and initialize Axe DevTools for Web, it needs to be installed first. If you haven't yet, read the guide on how to install it from a bundle, from your artifact repository, or from Deque's Agora. You will also need Puppeteer installed.

Importing and Initializing

Import both Axe DevTools for Web and Puppeteer. The syntax depends on the language and module system your project uses. Pick the one that matches your project:

JavaScript with CommonJS modules

This is the default for a Node.js project without "type": "module" in its package.json.

const { AxeDevToolsPuppeteer } = require('@axe-devtools/puppeteer');
const puppeteer = require('puppeteer');

JavaScript with ES modules

Use this syntax in a project with "type": "module" in its package.json, or in .mjs files.

import { AxeDevToolsPuppeteer } from '@axe-devtools/puppeteer';
import puppeteer from 'puppeteer';

TypeScript

TypeScript uses the same import syntax as ES modules. @axe-devtools/puppeteer ships its own type declarations, so there is no separate @types/ package to install. Scan results are typed as AxeResults, which axe-core exports:

import { AxeDevToolsPuppeteer } from '@axe-devtools/puppeteer';
import puppeteer from 'puppeteer';
import type { AxeResults } from 'axe-core';

For each scan, a new AxeDevToolsPuppeteer object will be created.

Getting Scan Context

Before you can scan a page for accessibility, it needs to be accessed by Puppeteer.

//Launch the Puppeteer Driver
const browser = await puppeteer.launch();
//Create a new page in the browser
const page = await browser.newPage();
//Send the browser to the desired page to scan
await page.goto('$URL');

Bypassing Content Security Policy

If the page you are trying to scan has Content Security Policy enabled, you may have issues. If you encounter this problem, Axe DevTools includes a workaround. Simply include this statement after your page is created:

await page.setBypassCSP(true);

Once Puppeteer has accessed the page, you can scan it with Axe DevTools and save the results. The most simple way to view the results of the scan is to console log the results object.

const results = await new AxeDevToolsPuppeteer(page).analyze();
console.log(results);

Complete Sample File

The same test is shown below in JavaScript and in TypeScript. The Axe DevTools API is identical in both; the TypeScript version uses import syntax and annotates the values Puppeteer and the scan return.

JavaScript

const puppeteer = require('puppeteer');
const { AxeDevToolsPuppeteer } = require('@axe-devtools/puppeteer');

(async () => {

    //launch puppeteer web driver
    const browser = await puppeteer.launch();
    const page = await browser.newPage();

    //launch page for testing
    await page.goto('https://broken-workshop.dequelabs.com');

    //analyze page
    const results = await new AxeDevToolsPuppeteer(page).analyze();
    
    //log results
    console.log(results);

    //close webdriver
    browser.close();
})();

TypeScript

import puppeteer from 'puppeteer';
import type { Browser, Page } from 'puppeteer';
import { AxeDevToolsPuppeteer } from '@axe-devtools/puppeteer';
import type { AxeResults } from 'axe-core';

(async () => {

    //launch puppeteer web driver
    const browser: Browser = await puppeteer.launch();
    const page: Page = await browser.newPage();

    //launch page for testing
    await page.goto('https://broken-workshop.dequelabs.com');

    //analyze page
    const results: AxeResults = await new AxeDevToolsPuppeteer(page).analyze();

    //log results
    console.log(results);

    //close webdriver
    await browser.close();
})();

Next Steps

Now that you've successfully completed an accessibility scan, you're ready to move on to more advanced scanning topics like generating reports and using the results object.

Troubleshooting

If you have trouble with getting scan results, contact your Deque representative directly, reach us via our support desk, or send us an email. We'll be happy to help.