The quality of a test can't really be quantified; plus, as others have said, most posters forget to give karma points to good posters anyway.
Its true! and usually what gets the karma are things like 'you made a funny' or 'that is a nice wall of text [that I only half read]'
I was very sad at one point because I put a bunch of effort into drawing some what I considered to be quality fan art, and nobody gave any karma. But then I had to remind myself that people don't think about what actually took time and effort vs. random trolling.
(edit): Hey, I can add karma! I'm using IE6 (at work) with I guess flash 9 and when I click to add karma, nothing happens. However with the powers of the tab key I can find the karma box (where you can pick +1 karma or... well, thats the only option) then I press tab once, and I can type in a text box I can't see. Then tab one more time and <enter> and it processes. BOOM! karma is delivered