I know I can use Mobile-Friendly Test and PageSpeed Insights to test usability but is there a way to manually run Mobile Usability test direct from GWT? If I have to wait until GWT runs this test, how often does GWT re-generate Mobile Usability test report?
I would give Google at least 24 to 48 hours to update all results (including mobile usability) in your GWT account. If you can't wait that long then you should try using Google PageSpeed Insights to test your pages on demand and you will be notified right away if it believes the page is not mobile friendly.
Use this URL:
My report is 9 days old at this point. It is March 8th today and it was last updated on Feb 28th.
Like you, I am anxious to see this report updated. I fixed most of the issues on this site on March 2nd.
Google has just said that the mobile friendly algorithm will run in real time. That is, as they crawl pages, they will immediately asses whether or not they are mobile friendly.
I expect that the report will regenerate any day now. Nine days is a long period not have have updates in Google Webmaster Tools. Data usually lags by a day or two. Occasionally it lags longer. This is one of the longest lags that I have seen.
Here is what Google has to say about out of data data in GWT:
We're always working to increase the update frequency for your verified sites' data, such as crawl, index, and search query stats. Much of this data depends on the content of your site, and is a close approximation of the status of your site. Our internal systems are always changing, and the web itself is an ever-shifting ecosystem. In addition, there may be a lag between when the numbers are calculated and when they are visible to webmasters - although data gets published in intervals, we are continually collecting it. If your content doesn't change very often, or if you're not getting new links to your site, you may not see updates to your data every time you sign in to Webmaster Tools.
So even when they are not showing you the updates, they are collecting the data. A batch update will show that data in GWT shortly.