Hi,
I just use lower speed links in the lab (128/256k) using back to back DTE-DCE Cables, and set up the QoS Accordingly. I then just usually ftp a file from one side to the other with QoS enabled, and check the policies to make sure we are dropping the data as opposed to the voice.
Using lower speed links makes it easier to saturate with something like FTP, and then QoS can be disabled to show the effect,
HTH
Bill.