Sending the blade out to be tested is one option.
Although very crude and general in nature, another option would be using hardness testing files. But that merely gives a "ballpark estimate" at best.
Still, it is an economical means to check your methods when new to heat treating. I don't believe I would use it to compare methods, or even to compare different steels. Simply to know if the steel is "harder than this, but softer than that".
My impression about hardness testing is that it is destructive in nature. Meaning that "cleanup" is required, and you're left wondering if you have the same hardness throughout. Also, location of testing comes into play. I don't understand testing the tang when the true question concerns the blade, so the methods employed during heat treat are also considerations.
I have yet to have any of mine tested, but then again, making knives is something I do for my own purposes, not for intent of selling to others.
If the time comes when I do need to know, my machinist down the street can do it for a couple of beers.
For now, I do as I've always done- try the blade out under real-world conditions and see if I'm satisfied with it.
Someone like Kevin or anybody with more experience in this subject needs to provide you with more guidance, because I know just enough to get into trouble!:biggrin:
It is my understanding that this subject is a science unto itself!
Good Luck,
Rob