Unit testing code that uses HttpContext.Current.Session

http://www.necronet.org/archive/2010/07/28/unit-testing-code-that-uses-httpcontext-current-session.aspx/

In process of writing unit test for NecroNetToolkit (yes, I know I should have written tests first) I needed to test a proxy class that stores and retrieves values from HttpContext.Current.Session. It’s kind of pain, because you can’t mock HttpContext or the session state object. You could in MVC, where controllers have HttpContextBase, but you can’t do it withHttpContext.Current. I already had code for instantiating HttpContext, so I decided to try and ‘Inject’ the session into it.

I used reflector to find out, that the Session property actually returns HttpContext.Items["AspSession"]. So I created ttpSessionStateContainer, which is only parameter to HttpSessionState object. Only problem is that HttpSessionBase has internal constructors, so a little reflection magic is needed to instantiate it. And it worked! Now I can use HttpContext.Current.Session (at least to some extent) in unit tests. Here’s the code:

var httpRequest = new HttpRequest("", "http://mySomething/", "");var stringWriter = new StringWriter();var httpResponce = new HttpResponse(stringWriter);var httpContext = new HttpContext(httpRequest, httpResponce);var sessionContainer = new HttpSessionStateContainer("id", new SessionStateItemCollection(),                                                     new HttpStaticObjectsCollection(), 10, true,                                                     HttpCookieMode.AutoDetect,                                                     SessionStateMode.InProc, false);httpContext.Items["AspSession"] = typeof (HttpSessionState).GetConstructor(                                         BindingFlags.NonPublic | BindingFlags.Instance,                                         null, CallingConventions.Standard,                                         new[] {typeof (HttpSessionStateContainer)},                                         null)                                    .Invoke(new object[]{ sessionContainer});HttpContext.Current = httpContext;