public void ShouldBeAbleToUseDoForEach() { var simpleClasses = new List <SimpleClass>(); Action <MyClass, SimpleClass> action = (x, y) => x.Add(y); { operable.ObjectBuilder.Returns(objectBuilder); objectBuilder.DoMultiple(action, simpleClasses).Returns(objectBuilder); } OperableExtensions.DoForEach((IOperable <MyClass>)operable, action, simpleClasses); }