We have a viewsonic tv and the remote control has stopped working after just two years. How do we now if it is the tv that the problem is or the remote

Okay here's the fix.
Remove batteries. Re-install them wrong side in! Don't panic. 
Reverse the direction of both the battery cells and install. Press "Power" button a couple of times and a few other buttons a few times. Then remove batteries and re-install the right side in.
Voila.

Testing remote control:
The remote control puts out IR (InfraRed) signal that human eyes cannot see, to find out if the remote is sending out the signal or not you just point the remote at the digital camera's Lens (Digital Camera can detect IR), you should see flashing light on the camera's screen when any one of the remote button is pushed. If you do see the flashing on the camera, then the problem is in the TV IR receiver or the main logic board; more troubleshooting with scope will be needed to look at the signals. I would get original from Viewsonic to get full functions. Look out for caps to go bad in your power supply also.
www.viewsonic.com
Parts: www.shopjimmy.com,
www.remotes.com
http://www.fixya.com/support/r5093881-lcd_flat_panel_tv_troubleshooting_guide

Failed TV and Monitors: http://s807.photobucket.com/home/budm/allalbums

http://en.wikipedia.org/wiki/Capacitor_plague