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Question

The particular class I'm testing depends upon the HttpSessionState object.

The HttpSessionState class has no public constructors. The class under test is only using this object as a NameValue store. The class is used in an ASMX web service to return information for a particular method.

I'm thinking about creating a facade around the HttpSessionState class where I can provide a Dictionary <string, string> instead of the Session object in testing.

Is this a good idea or standard practice?

Answer 1

Yep, as the old saying goes, there's nothing that can't be solved by adding another layer of abstraction. I usually just hide the type behind an interface where the interface's methods are the only ones needed to perform the actions I want on that type.

Just mock the interface that hides HttpSessionState, and do Asserts on the uses of the interface, in Rhino Mocks it's just AssertWasCalled(d => ....) etc.

Answer 2

You can create a sub-class of the HttpSessionStateBase class. This answer shows how to implement this for Moq, but you can still use the MockHttpSession class with your Rhino Mocks (I assume. I haven't used Rhino Mocks).

public class MockHttpSession : HttpSessionStateBase
{
    Dictionary<string, object> sessionStorage = new Dictionary<string, object>();

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

A fairly extensive discussion about how to mock .NET classes can be found at Scott Hanselman's blog here .

Answer 3

You can mock any type even sealed ones using Microsoft's Moles Isolation framework for .NET . Takes a little work to setup but might be better than adding another layer of abstraction. Mocking HttpContext and HttpSessionState using moles is discussed here . There is another similar discussion here .