I have just spent the entire day playing with Moq to unit test an asp.net mvc application I am working with. All I wanted to do is test a “create” method that simply adds a record to the database. So here it goes.

1. I created a Mock Http context to be used by my controller. I modified the Moq version of the MvcMockHelpers class from Scott Hanselman and added two more methods to mock an authenticated user

public static HttpContextBase FakeAuthenticatedHttpContext()
{
var context = new Mock<HttpContextBase>();
var request = new Mock<HttpRequestBase>();
var response = new Mock<HttpResponseBase>();
var session = new Mock<HttpSessionStateBase>();
var server = new Mock<HttpServerUtilityBase>();
var user = new Mock<IPrincipal>();
var identity = new Mock<IIdentity>();

context.Expect(ctx => ctx.Request).Returns(request.Object);
context.Expect(ctx => ctx.Response).Returns(response.Object);
context.Expect(ctx => ctx.Session).Returns(session.Object);
context.Expect(ctx => ctx.Server).Returns(server.Object);
context.Expect(ctx => ctx.User).Returns(user.Object);
user.Expect(ctx => ctx.Identity).Returns(identity.Object);
identity.Expect(id => id.IsAuthenticated).Returns(true);
identity.Expect(id => id.Name).Returns("test"); 
    return context.Object;
}

public static void
SetFakeAuthenticatedControllerContext(this Controller controller)
{
var httpContext = FakeAuthenticatedHttpContext();
ControllerContext context =                  
new ControllerContext(
new RequestContext(httpContext,
new RouteData()), controller);
controller.ControllerContext = context;
}

Note that the identity.Name returns “test” which is the username of an existing user in the database. If I don’t do that then the MembershipProvider.GetUser method will fail.

2. I added a couple of properties to my test class (MessageControllerTest) to make it easy for me to access the controller and view engine in all the test methods

private FakeViewEngine _fakeViewEngine;
public FakeViewEngine FakeViewEngine
{
get
    {
if (_fakeViewEngine == null)

              _fakeViewEngine = new FakeViewEngine();
return _fakeViewEngine;
}
}

private MessageController authenticatedController;
private MessageController AuthenticatedController
{
get
    {
if (authenticatedController == null)
{
authenticatedController = new MessageController();
authenticatedController.ViewEngine = FakeViewEngine;
authenticatedController.SetFakeAuthenticatedControllerContext();
}
return authenticatedController;
}
}

3. I created my test method which is going to call a Create method in my MessageController and pass it a string.

[TestMethod]
public void Create_Message_Test()
{
AuthenticatedController.Create("This is a test message");

//verify
    Assert.AreEqual("Json", FakeViewEngine.ViewContext.ViewName);
Assert.IsInstanceOfType(FakeViewEngine.ViewContext.ViewData,

                             typeof(MyViewData));
Assert.IsTrue(((MyViewData)FakeViewEngine.ViewContext

                            .ViewData).isSuccessful);
Assert.IsNotNull(((MyViewData)FakeViewEngine

                            .ViewContext.ViewData).Id);

using (MyDataContext dc = new MyDataContext())
{
var query =
dc.Messages.Where(
m => m.MessageId ==
((MyViewData)FakeViewEngine

                       .ViewContext.ViewData).Id);
//verify it was added to the database
        Assert.AreEqual(1, query.Count());

//delete it
        dc.Messages.DeleteOnSubmit(query.First());
dc.SubmitChanges();

//verify it was delete
        Assert.AreEqual(0, query.Count());
}
}

Note that in the verification block, I verify:

1. The view being rendered
2. The returned type of the ViewData
3. Properties on the ViewData

Then I clean up the created message by deleting it from the database.

Important:

You must add your connection strings and membership definition in an app.config file in your test project. If you don’t then the default consrtuctor of your DataContext will fail to run because it looks for the connection string in the config file.

I am still wrapping my head around the concept of mocking, so any tips or advice will be appreciated.

Here are some good resources that I found during my struggle to get this to work.

ASP.NET MVC Resources

1. ASP.NET MVC Framework – Part 2: Testing
2. ASP.NET MVC Session at Mix08, TDD and MvcMockHelpers

LINQ to SQL Resources

1. Being Ignorant with LINQ to SQL

Testing and Mocking Resources

1. Moq: Linq, Lambdas and Predicates applied to Mock Objects
2. Moq
3. Rhino Mocks
4. TDD: Test-Driven Development with Visual Studio 2008 Unit Tests