Screen resolution vs Resizing a window in Selenium


The main product I test was designed to follow a responsive web design layout so it could theoretically be used on anything from desktop computers to tablets and smartphones. Practically speaking this means different viewable window sizes (viewport sizes) will result in the browser placing elements of our application in different locations on the screen. When running my selenium acceptance tests I wanted to be able to specify different viewport sizes both locally and remotely on Sauce Labs. While the sizes may not make a difference to Selenium they give me another variable to specify if I so choose to do responsive testing. The examples I found weren’t very helpful so I decided to make my own for both.

Resizing your window. Locally the browser can be resized to a specific width and height by using the resize_to() command. For a window size of 1280×1024 the line of code we are looking for is:

window.resize_to(1280, 1024)

In my selenium-examples repo this code goes into the spec_helper file and looks like @driver.manage.window.resize_to(1280, 1024) as you see on line 20:

If you don’t use a helper spec you can include this code in your setup method or right after you call WebDriver.

Setting screen resolution. Resizing your window works great locally but what if you want to run your tests remotely at Sauce Labs? How do we ensure our screen resolution is large enough to support a larger window size? Luckily Sauce Labs opens their browsers to the maximum window size so all we have to do is set the screen resolution.

According to the Sauce Labs’ configurator we want to use the ‘screenResolution’ method like they show below:

caps = Selenium::WebDriver::Remote::Capabilities.chrome caps['platform'] = 'Windows 8' caps['version'] = '43.0' caps['screenResolution'] = '1280x1024'

If we go back to the example-selenium repo you’ll see I’m actually using caps[“screenResolution”] = ENV[‘resolution’] in the above spec_helper at line 11.

I’m setting a global variable for screen resolution so I can update it in the config_cloud file as I might update other global settings like operating system or browser version. This is important because in some cases, I may have to either adjust the resolution size or in the case of Safari, actually comment it out. For some reason Sauce Labs doesn’t have many resolutions options for Mac OS X, which is a bit annoying. The latest versions of OS X don’t even support resolutions of 1280×1024.

  • Selenium Guy

    I think this is currently broken in Chrome. Doesn’t seem to work for me.