The Tape test facility test multiple tape drives simultaneously. Another way to do this with the 32 bit product is to run multiple copies of SCSIPro 32 at the same time.

You must set the the multiple command option to on (options, multiple commands, on) and you must select a tape drive or  Tape Test Facility will  not be highlighted. 

In the screen shot below and above tape drives with scsi id 4 and 5 on controller 1 have been selected.