[DonRotolo]

A quick review of the test proposal seems good.
I would extend the test period to 1 minute instead of 15 seconds. You'll catch more faults that way.
20A is a good load for these batteries. 7A is good too (that is, 1A is too small, 40A is too large)

What is missing here is your definition of "bad". You are using a State of Charge measurement (terminal voltage) to evaluate battery Condition. While this is a common practice, it is not ideal. A battery with a good state of charge can be in poor condition, and vice-versa. The concern for FRC teams is battery condition prior to attending a competition, and state of charge at a competition.

(some) Modern battery test systems use internal resistance as an indicator of battery condition. I can't get into the details, but Google "Midtronics Battery Tester" to get more info at the Midtronics site.