Agreed. I don't know of any effective testing method for rock, other than the vingar test which only tells us if it will affect pH to some degree. In reality, all that really tells us is that the rock is basic in nature and reacts when exposed to a weak acid, so in water it will slowly break down and increase the alkalinity of the water.
Trial and error seems to be far more the order of the day when you are trying different types of rock that cannot be positively I.Ded.