If quantum mechanics is to be considered a fundamental theory, why are macroscopic objects never found to exhibit the principle of superposition, a phenomena so prevalent in small systems? The success achieved by quantum mechanics in laboratory predictions together with this contradiction of everyday experience has raised the question as to whether quantum mechanics is an approximation of a more general theory, one which betters explains the lack of observed superposition at large scales. The field of optomechanics has created the possibility to control and measure quantum motion of macroscopic mechanical systems, which would allow for tests of novel decoherence mechanisms. I discuss a scheme for such tests in a system of two entangled mechanical resonators.