I've heard people compare it to the AKC CGC program (that's Canine Good Citizen), but although the goals are similar (good, happy, well-behaved dogs), I think the two test different things. The CGC tests how well trained your dog is; the T-Test tests your dog's innate reactions. For example, although Porter passed her CGC test swimmingly, she had a lot of trouble with (and actually almost failed) her T-Test because she completely freaked out when she heard the gunshot, among other things. Eventually she calmed down, but the judge told us that was an area that we needed to be watchful of. (And we knew that--Port hates both thunderstorms and fireworks.)
Admittedly, it seems like this is a test a lot of people do with dogs they want to breed as opposed to house pets, but, really, I find the whole process interesting enough that it's fun for me to do even though both dogs are fixed. And, although in Porter's case it was pretty obvious where her problem would be, with Moe I wasn't so sure. I thought it would be interesting to see what, if anything, he had aversions to--it's a good thing to know and be able to work on.
So, off for temperament testing we went.
The judge was actually pretty surprised at Moe. Afterwards he told me that dogs usually start out well, and then progressively do worse--Moe did just the opposite. He almost completely ignored the neutral and friendly strangers at the beginning of the test, but investigated the noise in the bucket in true terrier style. He didn't have any trouble with any of the awkward footing or with the gun shot. And when the aggressive stranger came towards me at the end he went right to the end of his leash trying to go check her out. The judge said that he did very well, and that he is "a very confident little dog". Yup, pretty much, that's Moe. Here's a picture of him with the unfriendly stranger, and there are futher pictures of the test here.
Far more interesting to me than Moe's individual results, is a comparison of his results with Porter's. I think, if given the choice between Port and Moe, probably 80% of the people I know would choose Porter. Superficially, she's the gentle sunshine after Moe's hurricane. But outside of their normal environment, and especially with kids, I'd pick Moe every time. Porter seems mellow, but when she gets afraid it's not pretty. Moe on the other hand--while he might get over-exhuberant--is much more sensible. The T-Test really showed their underlying personalities, i.e. Porter's tendancy to come to pieces when stressed translated to an almost failure vs. Moe's "whatever" attitude translated to a more sucessful pass.
That's probably more than you ever wanted to know about temperament testing, but, truly, if there's one near you sometime it's worth doing.