More robust site testing can now be done by changing your viewport size!
Found in the Advanced Tab of Site Settings, Administrators and Managers can specify the page size they want tested by DubBot. This allows for specifically testing a mobile view of websites.
The next site crawl will use the entered width and height for analysis and your pages will be seen at this new size as well.
Details for the viewport size being tested can be seen/confirmed in the Network tab on the Detail Page View.
Learn more about what you can find in the Advanced Settings for Sites.