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How to Use Chrome DevTools Protocol in Testplane

Introduction​

warning

Install Hermione (Testplane) version 4 or higher in your project to use Chrome DevTools Protocol (CDP) in Testplane tests.

The WebDriver protocol has been used in Testplane for a long time, but the possibility of using CDP appeared only after migrating to WebdriverIO@7 in Hermione version 4.

CDP support in WebdriverIO@7 is implemented using puppeteer, which is a wrapper with a convenient API over CDP.

For a comparison of the WebDriver and CDP protocols, see the "WebDriver vs CDP" section in the Reference Manual.

Local Usage​

To work with the browser via CDP locally, add the automationProtocol: 'devtools' option to the browser settings in the Testplane config:

// .testplane.conf.js

module.exports = {
    browsers: {
        chrome: {
            automationProtocol: "devtools",
            desiredCapabilities: {
                // ...
            },
        },

        // other browser settings...
    },

    // other Testplane settings...
};

After this, all subsequent runs will be performed in your locally installed Chrome.

But if you need to run a browser with CDP support just once, it's more convenient to override this option using an environment variable:

testplane_browsers_chrome_automation_protocol=devtools npx testplane ...

Or set it as a CLI option:

npx testplane ... --browsers-chrome-automation-protocol=devtools

Remote Usage​

When using CDP on a remote machine (e.g., in a grid), Testplane will first start the browser using the WebDriver protocol and then, upon user request (i.e., when calling a CDP command), switch to CDP connection. Thus, in a single test scenario with a remote browser, we will interact using both protocols.

It looks something like this:

Remote CDP Usage Diagram

To connect to a remote browser via CDP, you need to:

  • use automationProtocol: webdriver (default value);
  • add the vendor-specific field selenoid:options in the browser’s desiredCapabilities: this option is necessary for webdriverio to understand that it needs to connect to a remote machine instead of a local browser.
// .testplane.conf.js

module.exports = {
    browsers: {
        chrome: {
            desiredCapabilities: {
                "selenoid:options": {},
                // ...
            },

            // other browser settings...
        },

        // other browser settings...
    },

    // other Testplane settings...
};
Limitations

Full CDP usage is only supported from Chrome@77 and higher. This is due to the internal implementation in webdriverio.

What Capabilities Does CDP Provide​

With CDP, you can: