We use Snapshots in our production system, what I am wondering is whether the snapshots for the tests were on the same disks as the main database file, or seperate ones, and also whether the snapshots themselves were on seperate disks?

People should also be incredibly wary of putting a snapshot on the same disk as a DB, due to the nature of how snapshots work they become very fragmented (this should probably be addressed by MS), should your filegroup grow on that disk then the fragmentation will carry over to that too, leading to a performance loss.