Now that I'm in front of a computer again, the Class rating tests I was referring to earlier are the UL 2218, UL 2218-B, and the FM 4473.

UL 2218 is done with steel balls. A steel ball is dropped TWICE on the same spot for each test, and shingles are struck in the field, on edges, and on unsupported areas. After the two impacts, in order to pass for each particular class rating, the shingle must show NO evidence of tearing, fracturing, cracking, splitting, rupturing, crazing, or other evidence of an opening on either the top or the bottom of the shingle. Each area is inspected under 5x magnification. For the UL 2218 test specifically, the class ratings are as follows:
Class 1 -- 1 1/4" steel ball dropped from 12 feet.
Class 2 -- 1 1/2" steel ball dropped from 15 feet.
Class 3 -- 1 3/4" steel ball dropped from 17 feet.
Class 4 -- 2" steel ball dropped from 20 feet.

The other two tests use ice balls of the same size, with minimum weights, speeds, and energy (ft/lb). Looks like the ft/lb rating on a Class 4 shingle is 26.81 ft/lb.

Here are some videos of testing from Haag Engineering. This one is newer and has the best images.



I like this one of a 1 3/4" ice ball on an S-tile. They have another video where they do the same size steel ball drop test and it shatters the tile.


Finally, take a minute to find out where your house is with respect to wind zones. You probably aren't in an area that needs more than 110mph rated shingle, but have this discussion with your roof contractor. He'll tell you what they are installing, and can show you the manufacturer recommended nailing pattern for installation in your wind zone. It looks like the wind testing can be found by searching for ASCE-7. If you can't get your contractor to walk you through the process on how they'll install everything, probably find a different one.