public void Manually_Remove_Reference()
        {
            using (var personsContext = new PersonsContext(DbContextOptions))
            {
                var him = new Person {
                    Id = 1, Name = "Him", SpouseId = 2
                };
                var her = new Person {
                    Id = 2, Name = "Her", SpouseId = 1
                };

                personsContext.Persons.Add(him);
                personsContext.Persons.Add(her);
                personsContext.SaveChanges();
            }

            using (var personsContext = new PersonsContext(DbContextOptions))
            {
                var him = personsContext.Persons.Find(1);
                var her = personsContext.Persons.Find(2);
                him.SpouseId = null;
                personsContext.SaveChanges();
                her.SpouseId = null;
                personsContext.SaveChanges();
                personsContext.Persons.Remove(him);
                personsContext.SaveChanges();
            }

            using (var personsContext = new PersonsContext(DbContextOptions))
            {
                Assert.Null(personsContext.Find <Person>(1));
            }
        }
        public void OnDelete_SetNull()
        {
            using (var personsContext = new PersonsContext(DbContextOptions))
            {
                var him = new Person {
                    Id = 1, Name = "Him", SpouseId = 2
                };
                var her = new Person {
                    Id = 2, Name = "Her", SpouseId = 1
                };

                personsContext.Persons.Add(him);
                personsContext.Persons.Add(her);
                personsContext.SaveChanges();
            }

            using (var personsContext = new PersonsContext(DbContextOptions))
            {
                var him = personsContext.Persons.Find(1);
                personsContext.Persons.Remove(him);
                personsContext.SaveChanges();
            }

            using (var personsContext = new PersonsContext(DbContextOptions))
            {
                Assert.Null(personsContext.Find <Person>(1));
            }
        }