WDIO DevTools Service

With Chrome v63 and up the browser started to support multi clients allowing arbitrary clients to access the Chrome DevTools Protocol. This provides interesting opportunities to automate Chrome beyond the WebDriver protocol. With this service you can enhance the wdio browser object to leverage that access and call Chrome DevTools commands within your tests to e.g. intercept requests, throttle network capabilities or take CSS/JS coverage.

Note: this service currently only supports Chrome v63 and up!

Installation

The easiest way is to keep wdio-devtools-service as a devDependency in your package.json.

{
  "devDependencies": {
    "wdio-devtools-service": "~0.1.1"
  }
}

You can simple do it by:

npm install wdio-devtools-service --save-dev

Instructions on how to install WebdriverIO can be found here.

Configuration

In order to use the service you just need to add the service to your service list in your wdio.conf.js like:

// wdio.conf.js
export.config = {
  // ...
  services: ['devtools'],
  // ...
};

Usage

For now the service allows two different ways to access the Chrome DevTools Protocol:

Via cdp Command

The cdp command is a custom command added to the browser scope that allows you to call directly commands to the protocol.

browser.cdp(<domain>, <command>, <arguments>)

For example if you want to get the JavaScript coverage of your page you can do the following:

it('should take JS coverage', () => {
    /**
     * enable necessary domains
     */
    browser.cdp('Profiler', 'enable')
    browser.cdp('Debugger', 'enable')
 
    /**
     * start test coverage profiler
     */
    browser.cdp('Profiler', 'startPreciseCoverage', {
        callCount: true,
        detailed: true
    })
 
    browser.url('http://google.com')
 
    /**
     * capture test coverage
     */
    const { result } = browser.cdp('Profiler', 'takePreciseCoverage')
    const coverage = result.filter((res) => res.url !== '')
    console.log(coverage)
})

Via Event Listener

In order to capture events in the browser you can register an event listener to a Chrome DevTools event like:

it('should listen on network events', () => {
    browser.cdp('Network', 'enable')
    browser.on('Network.responseReceived', (params) => {
        console.log(`Loaded ${params.response.url}`)
    })
    browser.url('https://www.google.com')
})

Development

All commands can be found in the package.json. The most important are:

Watch changes:

$ npm run watch

Build package:

$ npm build

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For more information on WebdriverIO see the homepage.