public void Should_provide_correct_hash_codes()
        {
            var id1 = Guid.NewGuid();
            var id2 = Guid.NewGuid();

            var user1a = new DO(id1, 1);
            var user1b = new DO(id1, 2);
            var user2  = new DO(id2, 2);

            Assert.Equal(user1a.GetHashCode(), user1b.GetHashCode());

            Assert.NotEqual(user1a.GetHashCode(), user2.GetHashCode());
        }