Not sure how I Mock this simple Save(User user) method in my .NET code
[TestMethod]
public void GivenANewUserWithValidData_Save_ReturnsTheSameNewUserWithAUserIdDetermined()
{
    // Arrange.
    var const string passwordSalt = "V4BXAhmHq8IMvR7K20TgoQ=="
    var user = new User
                   {
                       DisplayName = "Test",
                       Email = "foo@foo.com",
                       PasswordSalt = passwordSalt ,
                       Password = "foobar".ToSha2Hash(passwordSalt)
                   };

    var mockUserRepository = new Mock<IRepository<User>>();
    mockUserRepository.Setup(x => x.Save(It.IsAny<User>())).Verifiable();
    // Configure this repo in our Dependency Injection.
    ObjectFactory.Inject(typeof (IRepository<User>), mockUserRepository.Object);

    // Act.
    using (new TransactionScope())
    {
        UserService.Save(user);
        UnitOfWork.Commit(); // <-- not sure about this.. currently it's still
                             //     an EntityFramework context.
                             //     I need to change this to.. something??

        // Assert.
        Assert.IsNotNull(user);
        Assert.IsTrue(user.UserId > 0);
    }
}

public class UserService : IUserService
{
    public UserService(IRepository<User> userRepository,
                       ILoggingService loggingService)
    {
        // .. snip ..

        public void Save(User user) { .. }
    }
}

> 1) How should I test a [UserService.]Save method?
     Should I care about the result? and
> 2) If i do care about #1 .. then how do i mock the
     result also, so I can test that

mockUserRepository.Setup(x => x.Save(user)).Callback(() => user.UserId = 10);
// mocking the value of 10 being insterted into the key