As I mentioned,, I didn't get to see how revolvers were test fired,, but I'd doubt it's more than a cylinder full. With the costs of ammo, and the time it takes,, the expense, and trying to meet production schedules,, I doubt it's more than a few rounds each.
UNLESS,, the tech doing the test firing thinks there's a problem. Then they may test a couple more rounds. Any guns not functioning properly will get pulled for additional inspection.
They do not want to spend too much time anywhere that slows production.
And the costs of ammo, when multiplied by the number of guns produced daily,, could add up to a substantial amount QUICKLY!
Think about the year Ruger did the "2 Million Gun Challenge." They built 2 million guns. If they fired just (2) rounds each,, that's 4 million rounds of ammo.
Manufacturers want to keep expenses down, and if they fired a magazine full or a cylinder full,, the expenses just went WAY up.