Mocking sealed classes without public constructors?

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?

score 8 · Accepted Answer · answered Feb 06 '12 at 04:15

8

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.

answered Feb 06 '12 at 04:15

Mark W

3,879
2
37
53

3

"there's nothing that can't be solved by adding another layer of abstraction" - except "to much layers of abstractions" =) – Restuta Feb 06 '12 at 04:17
I believe the original was, "there's nothing that another level of indirection can't solve." At some point though you won't be able to test a level, such as what you're hiding httpsessionstate in. Not familiar with it but guessing you can't really unit test it, but you can test the SUT if it's using a type like this to do "something". – Mark W Feb 06 '12 at 04:21
I don't care about original, it's just true =) – Restuta Feb 06 '12 at 09:24

score 2 · Answer 2 · edited May 23 '17 at 12:24

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.

edited May 23 '17 at 12:24

Community

1
1

answered Feb 06 '12 at 04:58

jhsowter

619
3
8

is the HttpSessionStateBase class is available for web services? – Peter Smith Feb 06 '12 at 08:03
@PeterSmith HttpSessionStateBase is in the System.Web namespace, if that's what you mean. – jhsowter Feb 06 '12 at 23:06

score 2 · Answer 3 · edited May 23 '17 at 12:33

2

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.

edited May 23 '17 at 12:33

Community

1
1

answered Feb 06 '12 at 05:19

Scott Lerch

2,620
1
23
34

2

I am not sure that to get another one project dependency, read as "brand new isolation framework" is simplier solution (read as better) that one tiny abstraction. – Restuta Feb 06 '12 at 09:26
@Restuta, yeah, you're probably right, but it's an option and answers at least the title of the question "Mocking sealed classes" – Scott Lerch Feb 06 '12 at 17:09

Mocking sealed classes without public constructors?

3 Answers3

Linked

Related