How do you mock the session object collection using Moq

I started with Scott Hanselman's MVCMockHelper, added a small class and made the modifications shown below to allow the controller to use Session normally and the unit test to verify the values that were set by the controller.

/// <summary>
/// A Class to allow simulation of SessionObject
/// </summary>
public class MockHttpSession : HttpSessionStateBase
{
    Dictionary<string, object> m_SessionStorage = new Dictionary<string, object>();

    public override object this[string name]
    {
        get { return m_SessionStorage[name]; }
        set { m_SessionStorage[name] = value; }
    }
}

//In the MVCMockHelpers I modified the FakeHttpContext() method as shown below
public static HttpContextBase FakeHttpContext()
{
    var context = new Mock<HttpContextBase>();
    var request = new Mock<HttpRequestBase>();
    var response = new Mock<HttpResponseBase>();
    var session = new MockHttpSession();
    var server = new Mock<HttpServerUtilityBase>();

    context.Setup(ctx => ctx.Request).Returns(request.Object);
    context.Setup(ctx => ctx.Response).Returns(response.Object);
    context.Setup(ctx => ctx.Session).Returns(session);
    context.Setup(ctx => ctx.Server).Returns(server.Object);

    return context.Object;
}

//Now in the unit test i can do
AccountController acct = new AccountController();
acct.SetFakeControllerContext();
acct.SetBusinessObject(mockBO.Object);

RedirectResult results = (RedirectResult)acct.LogOn(userName, password, rememberMe, returnUrl);
Assert.AreEqual(returnUrl, results.Url);
Assert.AreEqual(userName, acct.Session["txtUserName"]);
Assert.IsNotNull(acct.Session["SessionGUID"]);

It's not perfect but it works enough for testing.

Using Moq 3.0.308.2 here is an example of my account controller setup in my unit test:

    private AccountController GetAccountController ()
    {
      .. setup mocked services..

      var accountController = new AccountController (..mocked services..);

      var controllerContext = new Mock<ControllerContext> ();
      controllerContext.SetupGet(p => p.HttpContext.Session["test"]).Returns("Hello World");
      controllerContext.SetupGet(p => p.HttpContext.User.Identity.Name).Returns(_testEmail);
      controllerContext.SetupGet(p => p.HttpContext.Request.IsAuthenticated).Returns(true);
      controllerContext.SetupGet(p => p.HttpContext.Response.Cookies).Returns(new HttpCookieCollection ());

      controllerContext.Setup (p => p.HttpContext.Request.Form.Get ("ReturnUrl")).Returns ("sample-return-url");
      controllerContext.Setup (p => p.HttpContext.Request.Params.Get ("q")).Returns ("sample-search-term");

      accountController.ControllerContext = controllerContext.Object;

      return accountController;
    }

then within your controller method the following should return "Hello World"

string test = Session["test"].ToString ();

I just found a nice example of how the Oxite team fakes their HttpSessionState and maintains a SessionStateItemCollection collection within that fake. This should work just as well as a moq in my case.

EDIT:

URL for this example is http://oxite.codeplex.com/sourcecontrol/changeset/view/33871?projectName=oxite#388065

I've made a slightly more elaborate Mock than the answer posted by @RonnBlack

public class HttpSessionStateDictionary : HttpSessionStateBase
{
    private readonly NameValueCollection keyCollection = new NameValueCollection();

    private readonly Dictionary<string, object> _values = new Dictionary<string, object>();

    public override object this[string name]
    {
        get { return _values.ContainsKey(name) ? _values[name] : null; }
        set { _values[name] = value; keyCollection[name] = null;}
    }

    public override int CodePage
    {
        get { throw new NotImplementedException(); }
        set { throw new NotImplementedException(); }
    }

    public override HttpSessionStateBase Contents
    {
        get { throw new NotImplementedException(); }
    }

    public override HttpCookieMode CookieMode
    {
        get { throw new NotImplementedException(); }
    }

    public override int Count
    {
        get { return _values.Count; }
    }

     public override NameObjectCollectionBase.KeysCollection Keys
{
    get { return keyCollection.Keys; }
}

    public Dictionary<string, object> UnderlyingStore
    {
        get { return _values; }
    }

    public override void Abandon()
    {
        _values.Clear();
    }

    public override void Add(string name, object value)
    {
        _values.Add(name, value);
    }

    public override void Clear()
    {
        _values.Clear();
    }

    public override void CopyTo(Array array, int index)
    {
        throw new NotImplementedException();
    }

    public override bool Equals(object obj)
    {
        return _values.Equals(obj);
    }

    public override IEnumerator GetEnumerator()
    {
        return _values.GetEnumerator();
    }

    public override int GetHashCode()
    {
        return (_values != null ? _values.GetHashCode() : 0);
    }

    public override void Remove(string name)
    {
        _values.Remove(name);
    }

    public override void RemoveAll()
    {
        _values.Clear();
    }

    public override void RemoveAt(int index)
    {
        throw new NotImplementedException();
    }

    public override string ToString()
    {
        return _values.ToString();
    }

    public bool Equals(HttpSessionStateDictionary other)
    {
        if (ReferenceEquals(null, other)) return false;
        if (ReferenceEquals(this, other)) return true;
        return Equals(other._values, _values);
    }
}