Access SessionState from within an NUnit test

Your problem is straight forward. If you shift your code from a place that is executed after Session_Start global event, then you will see this problem go quite comfortably. As an example write your code in Page_Init event or override OnInit and do whatever you want to do with your Session there.

Hope this will work for you.

Did you enable the session state in the section as well?

 <system.web>
      <pages enableSessionState="true" /> 
 </system.web>

Or did you add this to the page?

 <%@Page enableSessionState="true"> 

And did you verify that the ASP.NET Session State Manager Service service is running? In your screenshot it isn't. It's set to start-up mode Manual which requires you to start it every time you want to make use of it. To start it, highlight the service and click the green play button on the toolbar. To start it automatically, edit the properties and adjust the Start-up type.

Or set the SessionState's mode property to InProc, so that the state service is not required.

 <system.web>
      <sessionState mode="InProc" />
 </system.web>

Check MSDN for all the options available to you with regards to storing data in the ASP.NET session state.

Note: It's better to have your Controller fetch the value from the session and have it add the value to the Model for your page/control (or to the ViewBag), that way the View doesn't depend on the HttpSession and you can choose a different source for this item later with minimal code changes. Or even better, not use the session state at all. It can kill you performance when you're using a lot of async javascript calls.