Hi There
Not sure where I would post a suggestion. Testing adds in Android Studio/Eclipse is fairly easy thank to a certain miss Amy Quispe that helped me :-)
This made me think, perhaps Google can create a "TEST" feature in the Admob section where you create your Add account for your app/game and you can then select whether you want the specific account to be live or in test mode. Clicking in test mode would not do anything and serve test adds.
I don't know if this is something that would be easy or difficult to do, but it would also be able to help in cases such as game testing where implementing test adds in game development software is a nightmare for most people.
I'm just glad I know how to test my adds safely now :-)