IIRC, rockwell tests using a hardened steel ball, maybe a diamond? And recording how deep it impressed under a given pressure. The deeper, the softer. This is not an all-inclusive metallurgical test.
That should go deeper than the chrome plating (any sort of scratch test, however, would test just hte chrome alone).
However, tools that are case hardened, or even if they're tool steel through and through, they'll be softer in the middle where the quenching could not cool the steel as rapidly. An instron test, pulling or pushing or torquing the entire ratchet would be the best test. That would also reflect any structural defects that the rockwell test would not reveal: for example, pockets of impurities, or uneven alloying, or even perfect alloying but uneven hardening, won't necessarily reflect in a rockwell test that indents just a teensy bit of the surface, but such areas definitely DO act as stress concentrators that allow the ratchet to crack there under force. Rockwell hardness also does not address toughness, which a full tension, compression, and torque test of the entire piece would, to generate a stress:strain graph of the ratchet handle until the point that it broke.
X-ray diffraction, sonic tests, and probably some others can help to reveal internal defects as well.
A harder thing CAN be less tough, and more prone to fracture. You'd never want a tungsten carbide gear there, for example! Though it would be harder.
