Would that graph anything even if there is nothing being transmitted
Of course - you're just repeatedly measuring the voltage on a pin. If there's data there, then you'll see nice regular square-ish waves.
You could even feed it with the Tx pin from the other Arduino without using the RF, just to see what good data should look like.
Any way to test the receiver?
You mean the transmitter?
No, not really with this sort of setup (though an RF engineer will probably prove me wrong with a diode and some caps!)