I have done the CAD at both Citi Uni and the CAA, and be prepared for a less than pleasant experience.
The test will take between 12 and 15 minuets. You sit with your chin on a rest staring at the center of a CRT with a box in your hand that has 4 buttons. Top Left, Top Right, Bottom Left, Bottom Right, you have to press the button to the corner where you think the box is going. The test is taken in subdued lighting conditions.
I personally left the test with my eyes streaming and feeling totally drained. Just try playing that demo for 15 minuets with your head held in a single position, the lights off and the pressure of the rest of your life depending on your results!!
Myself I failed, but there I have failed all the CAA tests and the anomalascope at Citi. In fact the only test I have passed is the PRACTICAL FAA Tower Signal Test and I have my LOE and an unrestricted FAA medical. Great because I am a UK citizen with no right to work in the US.
The CAD is just another useless piece of junk that continues the academic wet dream of the CAA - and gives them a lot of brownie points along the way, and perhaps riches as well!! - ohhhh did I say that.
All the best with the test - I hope you DO pass. Just do what you can before to go in feeling your best, and on top of the world. If you are doing it as part of your C1 then ask to have the CAD as your first test, if you have it later the other tests will have worn you down a bit.
Hope this helps.