1. A method for generating a simulation module to facilitate testing a system design, comprising: receiving a system specification specifying correct behavior for modules within the system design; receiving a plurality of modules that are individually designed to the system specification; comparing the plurality of modules with the system specification to identify a nonfunctioning module, wherein the nonfunctioning module includes either a missing module or an incorrect module; determining from the system specification an interface specifying input and output requirements for the nonfunctioning module; and generating the simulation module, wherein the simulation module can function in place of the missing module and simulate a functionality assigned to the nonfunctioning module.