public IActionResult AddPerson(Person person)
 {
     // Let db assign id
     person.Id = Guid.Empty;
     _context.Add(person);
     _context.SaveChanges();
     return Ok();
 }
        public void Add_person_saves_to_db_with_generated_id()
        {
            // Arrange
            Guid personId = Guid.NewGuid();
            Person person = new Person()
            {
                Id = personId,
                FirstName = "Billy",
                LastName = "McBill"
            };
            var beforePersonCount = _context.People.Count();

            // Act
            var result = _controller.AddPerson(person) as HttpStatusCodeResult;

            // Assert
            Assert.Equal(200, result.StatusCode);
            Person savedPerson = _context.People.Single(x => x.FirstName == "Billy"
                                                             && x.LastName == "McBill");
            Assert.NotEqual(personId, savedPerson.Id);
            Assert.Equal(beforePersonCount + 1, _context.People.Count());
        }