Google has many updates to their Structured Data Testing Tool since launching in 2009, including renaming it in 2012 but yesterdays update may be one of the larger updates.

Google made the tool a lot easier to use and vastly improved the documentation around it. The updates include:

Validation for all Google features powered by structured data
Support for markup in the JSON-LD syntax, including in dynamic HTML pages
Clean display of the structured data items on your page
Syntax highlighting of markup problems right in your HTML source code

Here is a screen shot of the testing tool testing out my video page:

Perfect!

Google shared a photo of how it looks when it spots an error:

Plus, they revamped all the documentation around this, so you want to take a look, especially at the guidelines.

Forum discussion at Google+.