Sun have made some free pre-assessment tests available.
Just for fun, I went through the UNIX Essentials one. Would I pass? (Given that I have never had any formal training and have a rather eclectic skills mix it's not a foregone conclusion.)
According to the test, yes. I got a whopping 37/42 which is clearly enough to pass.
I suspect, though, that this says more about the accuracy (and grammatical validity, in one case) of the questions. One of the questions was incapable of being parsed into english, and I had to guess at random. Another one had two possible correct answers depending on factors you weren't told about. Another one had no correct answer on a vanilla Solaris system. There were a couple of questions that I looked at and thought to myself 'you wouldn't ever do it like that'.
(Plus a couple of questions on stuff that I would never use under any circumstances. I had a similar test when I applied for my current job, and my answer to every question mentioning vi was ':q' and use a proper editor.)
I tried the SCSA sample tests - scoring a little better on the part I test, and slightly lower on the part II. But again, there were questions that were simply wrong; some where the correct answer would always be 'look it up in the man page'; some artificially contrived questions; and I'm more than a little concerned about the coverage and subject matter. And on the SCSA tests there are a couple of areas where I haven't done much for a few years now (my OBP and LDAP skills are obviously getting a little rusty).