You can test an IR emitter by aiming just about any digital camera (that has a real-time display, meaning not a SLR) at it and watching the display as you drive the emitter. IR shows up as purplish-white on my pocket camera and Droid X phone. If all you have is a digital SLR you can use it too, but to see it you'll have to snap a pic while driving the emitter.
(P.S.: Some SLRs have a real-time display as well as the usual optical through-the-lens viewfinder. Those should work same as a point-and-shoot for this.)