On a draft news email, Send a test to me now sends the test while you stay on the page. The editor keeps the view you were writing in, Markdown or Formatted, and a message says where the test went. Before, the page reloaded and the editor opened in the Formatted view.
Sending a test news email keeps your place
Send a test to me sends the test without reloading the page, so the editor stays in the Markdown or Formatted view you were using.