The employment of path entangled multiphoton states enables measurement of phase with enhanced precision. It is common practice to demonstrate the unique properties of such quantum states by measuring super-resolving oscillations in the coincidence rate of a Mach-Zehnder interferometer. Similar oscillations, however, have also been demonstrated in various configurations using classical light only; making it unclear what, if any, are the classical limits of this phenomenon. Here we derive a classical bound for the visibility of super-resolving oscillations in a Mach-Zehnder. This provides an easy to apply, fundamental test of non-classicality. We apply this test to experimental multiphoton coincidence measurements obtained using photon number resolving detectors. Mach-Zehnder super-resolution is found to be a highly distinctive quantum effect.