You won't want to use the design mode as your testing mode because of the reason you're mentioning. You could use a macro and hide/show the web parts based on the ViewMode but the downfall then is you won't have any styling or JS files applied when viewing in the design mode.
Best bet is to leave it the way it is and do your testing in Preview mode or have a different browser open where you aren't logged into the Admin interface to perform your testing.