I went to a Trek store to get a new chain and cassette - the chain had a broken link. The tech on duty used a Park CC-3.2 chain checker. He used the .75 side of the checker and since it didn't fall through the chain he said that meant that the cassette was good and didn't need to be replaced - made no sense to me but hey, he works on bikes all day so I deferred to his "expertise". He was sure I could get another chain's worth of use out of it. The chain had a broken link so obviously it needed to be replaced. Subsequent testing showed me the cassette wasn't good - it was slipping on a brand-new chain. I got a cassette elsewhere which I installed myself and the slipping disappeared. Obviously the Trek tech's "test" failed.

Have you ever heard of the above outlined use of a chain checker to evaluate the condition of a cassette? Would you view this as a valid test for a cassette or is this tech just an idi...um, misguided?