상속: INotifyPropertyChanging, INotifyPropertyChanged
        public void SetUp()
        {
            _eventBroker = Substitute.For<IEventBroker>();
            DomainEvents.SetEventBrokerStrategy(_eventBroker);

            _fred = new Student();
            _law = new Subject();

            // Act
            _fred.EnrolIn(_law);
        }
        public void TheyShouldNotBePermitted()
        {
            var fred = new Student();
            var law = new Subject
            {
                MaxStudents = 0,
            };

            fred.EnrolIn(law);

            Assert.Inconclusive("This is our mission for tomorrow morning. We need to add a non-default constructor to our entity so that we can reliably create instances in a valid state.");
        }
 partial void DeleteSubject(Subject instance);
 partial void UpdateSubject(Subject instance);
 partial void InsertSubject(Subject instance);
 public void EnrolIn(Subject subject)
 {
     subject.AcceptEnrolmentFor(this);
 }
 public bool IsEnrolledIn(Subject subject)
 {
     return StudentSubjectEnrolments
         .Where(sse => sse.SubjectId == subject.Id)
         .Any();
 }