The Mech
Laser weapons contained plenty of tiny, delicate components, so they were also the weapons most prone to malfunction.
They first tested the missile launchers, but everyone knew it was just a formality. The launchers were fairly low-tech to begin with as most of the advances in missile technology lay in the missiles themselves. The launchers only stored the missiles and kept them from exploding when they got bumped or something. Both the long-range and short-ranged missiles flew from the launchers without a hitch, and detonated against a cratered hill exactly as expected.