Most test steps against HTML-based web applications don't use the mouse or keyboard. Instead they are able to inject Click or Select events against the element in question (e.g. a button or drop-down select). Unfortunately Silverlight and WPF applications do not allow Test Studio to inject these events. We have to simulate system wide mouse moves, clicks, and key presses instead.
This is why I do not believe automating your WPF app while it's minimized to the system tray is possible through our Framework. The app must be visible in its normal window state for test execution to function properly. When minimized, there is no window for Test Studio to act upon.
the Telerik team
Check out the Test Studio roadmap
to find out more about the new performance testing functionality coming in our R2 2011 release this September!
Have you looked at the new Online User Guide
for Telerik Test Studio?