public void DoesntUpdateNonExistingContact() { //Arrange var mockUnitOfWork = new Mock <IUnitOfWork>(); mockUnitOfWork .Setup(un => un.ContactRepository.GetByID(It.IsAny <int>())).Returns(() => null); mockUnitOfWork.Setup(un => un.ContactRepository.Update(It.IsAny <Contact>())); //mockUnitOfWork.Setup(un => un.Save()); IContactValidator contactValidator = new ContactValidator(mockUnitOfWork.Object); //act contactValidator.PutContact("0", new Contact() { }); //Assert //Retorna exception }