Although Romano cheese is traditionally made in Italy from ewe's milk (Pecorino) the following recipe is prepared for a 2 gallon version of cows milk (which would technically be called Vacchino Romano).
Strength is usually tested by measuring permanent deformation of the container. Hydrostatic testing is the most common method employed for testing pipes and pressure vessels. Using this test helps maintain safety standards and durability of a vessel over time.
RE: Hydrostatic pressure test increased? To pressure to increase by 25%, either the volume of the pipe bore must shrink by 25% or the absolute temperarture of water should increase by 25%. I do not think these are possible to be missed during conducting the test.