When formulating a test plan for your responsive websites, it's important to strategically define the right mobile devices and desktop browsers for your manual and automated testing.
For mobile device testing, you can use your own customer analytics together with market data to complement your coverage, or leverage reports such the Digital Test Coverage Index Report.
For desktop web testing, you should also look into your web traffic analytics to understand which are the top desktop browsers and OS versions you should be testing against. You can also use the Digital Test Coverage Index report referenced above.
Related Post: Set Your Digital Test Lab with Mobile and Web Calendars
Test coverage is a cross-organizational priority where business, IT, Dev and QA should be consistently aligned with planning and priorities. Below is a recommended web lab configuration for Q1 2016 taken from our Digital Test Coverage Index. Note the inclusion of beta browser versions in the recommended testing mix due to the fact that browser updates often happen automatically and silently without the user knowing.
Once you've defined the mobile and web test coverage using the above guidelines, the next steps are to achieve parallel side-by-side testing for high efficiency, as well as keep the lab updated by revising the coverage mix once per quarter to make sure the devices and browsers you're testing on match your customer data and market share data.
As a recommendation, please review the mobile device coverage model below. It's organized into three groups: Essential, Enhanced and Extended. Each of these groups includes a mix of device types such as legacy, new, market leaders and reference devices (such as the Nexus devices).
To learn more, check out the Responsive Web Testing report.