Abstract: An apparatus for proof testing mechanical heart valve prostheses. The apparatus also provides an in vitro test environment simulating in vivo loads, providing a function test. If the heart valve passes the pivot proof test, a function test is performed. The apparatus first directs a pressurized back flow against the tested valve, closing the valve and applying pressure against the leaflet occluders well beyond the maximum functional in vivo load. The heart valve is positioned so that the leaflets assume their "worst-case" position, that is, the heart valve is oriented so that all the necessary play or gap between the leaflet pivots and pivot recesses is subsumed at one location, thus representing the most severe condition that might be experienced with a heart valve in use. The heart valve is loaded by back pressure applied through a working fluid. Pressure transponders detect the pressure on each side of the heart valve, to determine if a valid test has been performed.