1. A method performed by a computing device, the method comprising: generating, by a processor of the computing device, a graphical model representing a model-based design; associating, by the processor, a graphical postcondition element representing a postcondition with a portion of the graphical model; indicating, by the processor, in the associated graphical postcondition element, a desired result for verification; processing, by the processor, the graphical postcondition element into a postcondition specification; and providing, by the processor, the postcondition specification to a verification tool.