Question

I’m pretty new to testing and mocking and i am trying to write a test that will ensure that my validation logic is setting ModelState errors correctly.

What I’m seeing is that the controller.ControllerContext.HttpContext.Request is set the first time I check it but every time after that the Request is null.

This is causing a null reference exception in the PopulateDictionary method of the *ValueProviderDictionary * class in the MVC source because the request object is accessed multiple times in that method without ensuring the request is not null.

I’m gluing together several techniques and helpers that I have found while researching how to overcome some of the issues I have run into thus far so at this point I’m a little unsure where I may have introduced the issue.

Am I using mock objects incorrectly here?

Failing Test

//Test
public void Test_FooController_OnActionExecuting_ShouldMapStateToAFooModel()
{
    //Arrange
    DataAccessFactoryMocks.MockAllDaos();

    var controller = new FooController();

    var testFormCollection = new NameValueCollection();
    testFormCollection.Add("foo.CustomerID", "3");
    testFormCollection.Add("_fooForm", SerializationUtils.Serialize(new FooModel()));

    var mockHttpContext = new MockHttpContext(controller, "POST", testFormCollection, null);

    //Accessor used to run the protected OnActionExecuting method in my controller
    var accessor = new FooControllerAccessor(controller);

    //Request is set, assertion passes
    Assert.IsNotNull(controller.ControllerContext.HttpContext.Request.Form);

    //Request is null when accessing the property a second time, assertion fails
    Assert.IsNotNull(controller.ControllerContext.HttpContext.Request.QueryString);

    //Act
    accessor.OnActionExecuting(new ActionExecutingContext(controller.ControllerContext, MockRepository.GenerateStub<ActionDescriptor>(), new Dictionary<string, object>()));

    //Assert
    Assert.That(controller.ModelState.IsValid == false);
}

Test Helper

//Test helper to create httpcontext and set controller context accordingly
public class MockHttpContext
{
    public HttpContextBase HttpContext { get; private set; }
    public HttpRequestBase Request { get; private set; }
    public HttpResponseBase Response { get; private set; }
    public RouteData RouteData { get; private set; }

    public MockHttpContext(Controller onController)
    {
        //Setup the common context components and their relationships
        HttpContext = MockRepository.GenerateMock<HttpContextBase>();
        Request = MockRepository.GenerateMock<HttpRequestBase>();
        Response = MockRepository.GenerateMock<HttpResponseBase>();

        //Setup the context, request, response relationship
        HttpContext.Stub(c => c.Request).Return(Request);
        HttpContext.Stub(c => c.Response).Return(Response);

        Request.Stub(r => r.Cookies).Return(new HttpCookieCollection());
        Response.Stub(r => r.Cookies).Return(new HttpCookieCollection());

        Request.Stub(r => r.QueryString).Return(new NameValueCollection());
        Request.Stub(r => r.Form).Return(new NameValueCollection());

        //Apply the context to the suppplied controller
        var rc = new RequestContext(HttpContext, new RouteData());
        onController.ControllerContext = new ControllerContext(rc, onController);
    }

    public MockHttpContext(Controller onController, string httpRequestType, NameValueCollection form, NameValueCollection querystring)
    {
    //Setup the common context components and their relationships
    HttpContext = MockRepository.GenerateMock<HttpContextBase>();
    Request = MockRepository.GenerateMock<HttpRequestBase>();
    Response = MockRepository.GenerateMock<HttpResponseBase>();

    //Setup request type based on parameter value
    Request.Stub(r => r.RequestType).Return(httpRequestType);

    //Setup the context, request, response relationship
    HttpContext.Stub(c => c.Request).Return(Request);
    HttpContext.Stub(c => c.Response).Return(Response);

    Request.Stub(r => r.Cookies).Return(new HttpCookieCollection());
    Response.Stub(r => r.Cookies).Return(new HttpCookieCollection());

    Request.Stub(r => r.QueryString).Return(querystring);
    Request.Stub(r => r.Form).Return(form);

    //Apply the context to the suppplied controller
    var rc = new RequestContext(HttpContext, new RouteData());
    onController.ControllerContext = new ControllerContext(rc, onController);
    }
}

Working Test using MvcContrib.TestHelper

    public void Test_FooController_OnActionExecuting_ShouldMapStateToAFooModel()
    {
        //Arrange
        DataAccessFactoryMocks.MockAllDaos();

        TestControllerBuilder builder = new TestControllerBuilder();

        builder.Form.Add("fooModel.CustomerID", "3");

        builder.HttpContext.Request.Stub(r => r.RequestType).Return("POST");

        FooController controller = builder.CreateController<FooController>();

        var accessor = new FooControllerAccessor(controller);

        //Act
        accessor.OnActionExecuting(new ActionExecutingContext(controller.ControllerContext, MockRepository.GenerateStub<ActionDescriptor>(), new Dictionary<string, object>()));

        //Assert
        Assert.IsFalse(controller.ModelState.IsValid);
    }

Answer 1

I would suggest you using the excellent MVCContrib TestHelper for unit testing your ASP.NET MVC controllers with Rhino Mocks. You will see a drastic simplification of your unit tests and increased readability.