The new tool is available at https://search.google.com/search-console/amp and from within the Google Search Console.
The tool works on your mobile device and uses Google’s “live web-search infrastructure” to analyze the AMP page with the real Googlebot — so the result is done in real time. It tests the validity of the AMP markup and structured data on the page related to AMP.
If issues are found, you will be able to click on them to see details. Even the line in the source-code will be highlighted, showing you exactly where the error is.
It even has links to show you a live preview of how this page may appear in Google’s search results.
Here are screen shots: