1. A method, comprising: providing a waveform database for integrated circuit simulation, the database corresponding to several integrated circuit waveforms that each change in relation to a common period of time; applying a first assertion to the integrated circuit waveforms with a processing device, the first assertion being structured to test behavior of an integrated circuit design model corresponding to the integrated circuit waveforms; and evaluating the first assertion based on the applying; and in response to the evaluating, modifying the first assertion to provide a second assertion to test the behavior of the integrated circuit design model.