Abstract: A method for simulating operation of a design model for a digital system is provided. A library of functional cells is maintained in a storage unit that includes an attribute template with one or more of the functional cells in the library. The attribute template provides fields for specifying design constraint data for a functional cell each time it is instantiated in a design model. A design model is created and stored that includes one or more instantiations of a functional cell and its associated design constraint data. A set of test cases may be pruned to remove test cases that are not needed based on the design constraint data associated with the instantiated functional cells of the design model.