A system and method for generating executable units suitable for unit testing of a module for integration errors, the method comprising; recording, for a module, an interface specification that specifies pre-condition constraints on input values of methods of the module and post-condition constraints on output values of the methods of the module; creating, based upon the recorded interface specification, a driver unit for the module that complies with the pre-condition constraints specified by the interface specification; and creating, based upon the recorded interface specification, a stub unit for the module that checks compliance with the specified pre-condition constraints and that complies with the specified post-condition constraints of the interface specification.