Testing tools may include diamond grinding wheels, carbide or diamond tipped drills. They also use devices that apply high pressure on the cutter during the test. All tools must be portable. Testing and ratings only apply to the door, as this is the primary place safes are attacked. Anytime you see a UL label containing X6 then all sides were tested and certified.
Lets use some common sense.
With a safe you are only buying time. The better the safe the longer time you are buying. Of primary consideration is the type of threat you will experience. A professional will not be attacking a safe in a residential environment. If you are protecting the contents from Burglary get a good burglar safe, if you are protecting from fire get a good fire safe.