Mocking SQL output parameter - unit-testing

Question

I mocked a couple of methods of my Data Access layer, but in some methods the value of an SQL output param is set. How can I mock this ?
Method:
var wrappedParameters = new SqlParameter[3];
wrappedParameters[0] = new SqlParameter("#username",username);
wrappedParameters[1] = new SqlParameter("#password",password);
wrappedParameters[2] = new SqlParameter("returnValue",SqlDbType.Int) { Direction =ParameterDirection.ReturnValue };
dal.ExecuteUsingStoredProcedure("GetUser", wrappedParameters);
Mocking (I tried using "OutRef", but that doesn't work):
using (mocks.Record())
{
Expect.Call(dal.ExecuteUsingStoredProcedure("",> null)).Return(true).IgnoreArguments().OutRef(1);
}
But that didnt work. When I excute the SP GetUser the param return value is set, but I have no idea how to mock this

Answer 1

I think you're going about this the wrong way. Your DAL interface should look like this:
/// <summary>
/// Models a service which holds the user information.
/// </summary>
public interface IUserRepository
{
/// <summary>
/// Gets the user with the given name, or <c>null</c> if no user with
/// that name and password exists.
/// </summary>
/// <exception cref="IOException">
/// An I/O problem occurred while accessing the repository.
/// </exception>
User TryGetUser(string name, string password);
}
The DAL abstraction now hides the fact that a stored procedure is used. In fact, the DAL might not even be a database: it could be a text file on disk, a webservice, a mock or anything else.
Mocking the DAL in order to test code which uses the DAL now becomes trivial. I've chosen the view model (aka presentation model)of a login screen as the system under test in these examples:
[Test]
public void Login_sets_user_and_goes_to_main_screen_when_TryGetUser_not_null()
{
var userRepositoryStub = MockRepository.GenerateStub<IUserRepository>();
var user = new User(...);
userRepositoryStub.Stub(x=>x.GetUserByName("foo","bar")).Return(user);
var sessionStub = MockRepository.GenerateStub<ISession>();
var loginScreenViewModel =
new LoginScreenViewModel(sessionStub, userRepositoryStub);
loginScreenViewModel.UserName = "foo";
loginScreenViewModel.Password = "bar";
loginScreenViewModel.Login();
userRepositoryStub.AssertWasCalled(x=>x.TryGetUser("foo","bar"));
sessionStub.AssertWasCalled(x=>x.ShowMainScreen());
Assert.AreEqual(user, session.User);
}
.
[Test]
public void Login_shows_error_when_TryGetUser_returns_null()
{
var userRepositoryStub = MockRepository.GenerateStub<IUserRepository>();
var sessionStub = MockRepository.GenerateStub<ISession>();
var loginScreenViewModel =
new LoginScreenViewModel(sessionStub, userRepositoryStub);
loginScreenViewModel.UserName = "foo";
loginScreenViewModel.Password = "bar";
loginScreenViewModel.Login();
Assert.AreEqual(loginScreenViewModel.Error,
"User 'foo' does not exist or password is incorrect"));
userRepositoryStub.AssertWasCalled(x=>x.TryGetUser("foo","bar"));
sessionStub.AssertWasNotCalled(x=>x.ShowMainScreen());
Assert.IsNull(session.User);
}

Answer 2

I don't think you can mock it, because it is a normal SqlParameter (concrete class), and its not an out/ref parameter in .Net sense. What I would try is to simply set the value of the parameter in the mocked call to dal (I haven't checked the syntax, but I am sure you get the idea):
using (mocks.Record())
{
Expect.Call(dal.ExecuteUsingStoredProcedure("",null)).Return(true).IgnoreArguments().Do(x => wrappedParameters[2].Value = 1; true);
}

Answer 3

I stubbed this using the "WhenCalled" method.
In my code (to be tested) I first create the connection and command and add three parameters, the third of which is my output parameter. I then call "ExecuteCommand" on this....I won't go through the code for this as I think it's fairly standard (ExecuteCommand takes the command object as its parameter).
In my test, I create a stub for my sql data service and program it so that this sets the value of the parameter:
var sqlService = MockRepository.GenerateStub<ISqlDataService>();
sqlService.Stub(s => s.ExecuteCommand(null))
.IgnoreArguments()
.WhenCalled(s => ((SqlCommand)s.Arguments[0]).Parameters[2].Value = expectedValue)
.Return(0);
The answer's probably a bit late for your project, but hope this helps someone...
Griff