WebDriver is a remote control interface that enables introspection and control of user agents. As such it can help developers to verify that their websites are working and performing well with all major browsers. The protocol is standardized by the W3C and consists of two separate specifications: WebDriver classic (HTTP) and the new WebDriver BiDi (Bi-Directional).

This newsletter gives an overview of the work we’ve done as part of the Firefox 148 release cycle.

Contributions

Firefox is an open source project, and we are always happy to receive external code contributions to our WebDriver implementation. We want to give special thanks to everyone who filed issues, bugs and submitted patches.

In Firefox 148, a WebDriver bug was fixed by a contributor:

• Sameem added a helper to assert and transform browsing and user contexts in emulation commands.

WebDriver code is written in JavaScript, Python, and Rust so any web developer can contribute! Read how to setup the work environment and check the list of mentored issues for Marionette, or the list of mentored JavaScript bugs for WebDriver BiDi. Join our chatroom if you need any help to get started!

General

• Fixed a race condition during initialization of required browser features when opening a new window, preventing issues when navigating immediately to another URL.
• Fixed an interoperability issue between Marionette and WebDriver BiDi where the BiDi clientWindow ID was incorrectly used as a window handle in Marionette.

WebDriver BiDi

• Added initial support for interacting with the browser’s chrome scope (the Firefox window itself). The browsingContext.getTree command now accepts the vendor specific moz:scope parameter and returns chrome contexts when set to chrome and Firefox was started with the --remote-allow-system-access argument. These contexts can be used with script.evaluate and script.callFunction to execute privileged JavaScript with access to Gecko APIs. Other commands do not yet support chrome contexts, but support will be added incrementally as needed.
• Updated the emulation.setGeolocationOverride and emulation.setScreenOrientationOverride commands to implement the new reset behavior: contexts are reset only when the contexts parameter is provided, and user contexts only when the userContexts parameter is specified.
• Fixed a race condition in browsingContext.create where opening a new tab in the foreground could return before the document became visible.
• Fixed an issue that occurred when a navigation redirected to an error page.
• Fixed an issue in network.getData that caused a RangeError when decoding chunked response bodies due to a size mismatch.
• Fixed an issue where the browsingContext.userPromptOpened and browsingContext.userPromptClosed events incorrectly reported the top-level context ID instead of the iframe’s context ID.
• Improved the performance of WebDriver BiDi commands by approximately 100 ms when the selected context is no longer available during the command execution.

Marionette

• Added the Reporting:GenerateTestReport command to generate a test report via the Reporting API.