not matching correctly?

First, you shouldn't bother typing slashes like you do in your test/unit/ example. Typing testunit would work just as well. (And in fact, typing fewer characters like just test or even tu will probably get you there faster anyway.)

Secondly, Command-T looks at the entire path for possible matches, so it's not going to show you only matches from under the test/unit/ directory, but from anywhere in the project root. If you want to scope things just to the test/unit/ directory you can either launch Command-T with an explicit path argument (eg. :CommandT test/unit) or, preferably, get in the habit of using a character or two from each segment of the path. For example, to open test/unit/audit/patriot_act_audit_test you might type testaudpatact or perhaps patactaudtest. Depending on the number of files in your project you may find that you can use considerably less characters too.

Note that Command-T is not intended for file browsing (ie. "show me what files are in this directory") but is instead of quickly opening files in projects which you know well, and you know where the files are already and just want to specify them in the shortest manner possible.

Thirdly, which version of Command-T are you using? In version 0.8b the matching algorithm is greatly improved to give more intuitive match ranking, because instead of just assigning a match score to a path based on the first match it finds, it continues searching for possible better matches in each path and ends up using the highest possible score for each path.