Unit-testing an action which calls session object

Question

How can I unit test a method which uses a session object inside of its body?

Let us say I have the following action:

[HttpPost]
public JsonResult GetSear         


        

Answer 1

I've solved similar issues (use of static data accessors that aren't mock friendly - in particular, HttpContext.Current) by wrapping the access in another object, and accessing it through an interface. You could do something like:

pubic interface ISessionData
{
    ExtraFieldsLinker CurrentExtraFieldsLinker { get; set; }
}

public class SessionDataImpl : ISessionData
{
    ExtraFieldsLinker CurrentExtraFieldsLinker
    {
        // Note: this code is somewhat bogus,
        // since I think these are methods of your class.
        // But it illustrates the point.  You'd put all the access here
        get { return (ExtraFieldsLinker)GetSessionObject(EXTRA_FIELDS_LINKER); }
        set { SetSessionObject(EXTRA_FIELDS_LINKER, value); }
    }
}

public class ClassThatContainsYourAction
{
    static ClassThatContainsYourAction()
    {
        SessionData = new SessionDataImpl();
    }

    public static ISessionData SessionData { get; private set; }

    // Making this access very ugly so you don't do it by accident
    public void SetSessionDataForUnitTests(ISessionData sessionData)
    {
        SessionData = sessionData;
    }

    [HttpPost]
    public JsonResult GetSearchResultGrid(JqGridParams gridParams,
        Guid campaignId, string queryItemsString)
    {
        var queryItems = // ...
        IPageData pageData = // ...

        // Access your shared state only through SessionData
        var extraFieldLinker = SessionData.CurrentExtraFieldsLinker;

        // ...
    }
}

Then your unit test can set the ISessionData instance to a mock object before calling GetSearchResultGrid.

Ideally you'd use a Dependency Injection library at some point, and get rid of the static constructor.

If you can figure out a way to make your ISessionData an instanced object instead of static, even better. Mock object frameworks tend to like to create a new mock type for every test case, and having mocks lying around from previous tests is kind of gross. I believe session state is going to be global to your session anyway, so you might not have to do anything tricky to make a non-static object work.