Just what I have read online. Computer tests for maths, and interviews. And of course a tour of CX City.
wowpeter.com Blog Archive Cathay Pacific Cadet Pilot Program! [Updated with International Applicant Timeline / Info] is a good site to have a look at.
Also, I guess having some knowledge of FTA wouldn't go to far amiss.
I think the interviews took place over 3.5 days, with 3 or 4 each 0.5 day. so maybe a total of 20-25??? Don't really know