Testing bus transceivers

So, I have bought a number of DS8641 bus transceivers from a source in China, and cognizant of the claims that there are a lot of counterfeits coming from China, how can I test them to make sure the meet specs? I have a QBUS test board which I have constructed (it's basically just a single read/write register), so I can verify their _basic_ functionality; but the UNIBUS/QBUS specs give a number of analog qualifications, and it's those I'd like to check. Some of them I can figure out how to test, although a couple of them would seem to need special test rigs, e.g. input high threshold of 2.5V and low threshold of 1.4V, but I _think_ I can work out how to test those - a board with a pot on it, so I can vary the input voltage, and see where the output switches. (I'm not necessarily going to test every last chip, but I'd like to do random samples.) However, there are others of which I'm not at all clear how to test, e.g. output high leakage current of 25 uA. How would I test that? (And replies of the form 'use such and such an approach' probably aren't detailed enough for me - my analog-fu is pretty weak - so details would be most greatly appreciated! ;-) Noel