1. A simulation system for testing a simulation of a device against one or more violation rules, the simulation system comprising: a device simulator for executing the simulation of a device using a device design, a device model and a simulation scenario; and one or more violation monitors, one for each violation rule, at least one of the violation monitors comprising: a violation information detector for detecting one or more violations of the respective violation rule during the executing of the simulation and, for each violation, determining information representing the respective violation, wherein detecting the one or more violations comprises comparing a simulated parameter against a threshold, and a threshold controller for determining the threshold for the respective violation rule in dependence on a temporal characteristic of the associated violation.