To what extent do you test UI elements?

I'm new to Android testing. Well android development in general. I'm building an app and I want to perform instrumented tests, to test if the UI is working. My question is should I test every single UI element? Right now I'm launching an activity in an instrumented test class and testing whether each UI element is visible. It seems.. tedious. What other things should I test for? So far I only have buttons, text views, some third party graph view.