The best way to determine if your site passes Google's mobile-friendly litmus test is to head over to Google's Mobile Friendly Test. A page is eligible for the "mobile-friendly" label if it meets the following criteria as detected by Googlebot:

• Avoid software that is not common on mobile devices, like Flash
• Uses text that is readable without zooming
• Sizes content to the screen so users don't have to scroll horizontally or zoom
• Places links far enough apart so that the correct one can be easily tapped

Alternatively, you can use sites like mobiletest.me to ensure your site works properly across various types of mobile devices. But don't worry about that too much since only smartphones—not tablets—will be impacted. Also note that desktop rankings are not affected by this update.