GRJ's application is to test large batches whereas the rest of us would be testing much fewer. In case anyone missed it, what's neat about GRJ's tool are the spring-loaded test pins to make reliable contact to the 4 pads. These so-called "pogo pins" (like a kid's pogo stick) are not expensive but hard to imagine using them if assembling/testing just a handful of boards.
As GRJ states, the LED confirms capacitor operation. You see the brightness decay rather than going instantly dark. Note that GRJ mentions a high intensity LED that can presumably take the full current. So if using this for a 100mA board, use a suitable LED.
As for skipping the LED and hooking an ammeter directly across the board's output. A digital meter updates a few times per second so its numbers would jump making it tricky to see a smooth decay. An analog (needle) meter's spring slows the needle's return-to-zero and could be mis-interpreted as a smooth decay. Separately, if using a digital mA meter, most are fused when making mA-range measurements. Fuse values may be, say, 1/4 Amp or whatever. OTOH, using the 10 Amp setting may not give enough resolution when testing or calibrating the range of these low-current boards. So if the purpose of the mA metering is for test (before and as opposed to calibration), you may pop the mA fuse if there was an assembly error - fuse is replaceable but kind of a hassle.
