I assume what this test does is it simply tries to access a few security vendors web sites and comes up with clean after it is successful or infected if it is unsuccessful at accessing them. Since Conficker worm blocks access to those sites, that is i suppose the easiest way to tell if a computer is infected with Conficker or not. The .A variant is a different story though and this test doesn't detect it.
http://iv.cs.uni-bonn.de/wg/cs/applications/containing-conficker/