After it’s launch in November 2014, Google on 17th May 2016 has announced launch of their new mobile-friendly testing tool.
Yaniv Loewenstein from the Search Console Team wrote:
The new tool is available at the URL https://search.google.com/search-console/mobile-friendly
The older version is available at https://www.google.com/webmasters/tools/mobile-friendly
UI of older version
UI of new version
As compared to the older version, the new tool has got a captcha preventing the hits from automated bots. The UI is cleaner and provides you the blocked resources and next steps to be followed.
The next steps includes checking site-wide Google Search Console’s mobile usability report, learning about mobile-friendly pages and participation in discussion on Webmaster Central Help Forum.