how do you test a voltage regulator

[kxnomore]

This is the second time I've had a zero charging situation. The first time it happened I changed both the alternator and regulator. Things were fine for a few months, but now my battery is dead again, and again, there is no increase in voltage while the truck is running after jumping. The voltage at the battery is 10 volts running or not.

So rather than just start changing parts, does anyone have any good tips on the correct way to check the regulator? Do they fail often? I have a hard time believing it's the alternator, as these usually last a long time, I've always thought...

Thanks in advance to anyone who can help with this ongoing issue.

Here's a pic of the truck just because I know you all need pics!