Further testing methods I have done

If you have one torque wrench you know is calibrated
Using a 12 point socket is connecting it to another TW you want to see if it also is calibrated
set both to like 30 ft/lbs

Set the one that is known calibrated flat on a table and the other connected to it at n angle
Pull down on that one and see if both click when set at that 30 foot/pounds
If so, you're all done

If the TW under test is either clicking too early or too late then make calibration changes until both click at the same time

Also with the method I posted above

If you do not want the hassle of coming up with the weights needed, the string, etc

I tested using a cheap luggage weight scale, this one works up to 110 pounds
So simply put, fitting for sockets into a vise
do the same as above, set TW to like 30 ft/lbs
Measure the arm of wrench, mark that length on at point and write that down

Now place the luggage scale at that mark and pull it until TW clicks
Look at the reading of that scale and write that down and then do the simple math we used before

TW arm length times scale weight and divide by 12 if wanting results on ft/lbs