5 Model Programs

196 Testing Systems with Complex Stateusing System.Collections.Generic;using NModel;using NModel.Attributes;namespace BagModel{static class Contract{static Bag content = Bag.EmptyBag;[Action]static void Add(string element){content = content.Add(element);}[Action]static void Delete(string element){content = content.Remove(element);}[Action]static int Lookup(string element){return content.CountItem(element);}}}[Action]static int Count(){return content.Count;}Figure 12.2. Bag model.possible input parameters is to provide a separate feature of the model that allowsonly a fixed set of elements to occur as input arguments to the respective actions.Such a feature is shown in Figure 12.3. This feature restricts the set of possibleelements to null, "", and "b". It uses the Domain attribute to associate a fixed set ofelements with each input parameter.