How do I inject something into request header for testing? - asp.net-mvc-3

Question

I am currently implementing SiteMinder for the site, which looks for a key called SM_USER in the request header. I retrieve it using the function below:
public string ReadUser()
{
return HttpContext.Current.Request.Headers["SM_USER"];
}
I wish to test if functionality releated to this function work; I have already tried unit testing using a mock class so I am looking to create the key SM_USER in the request header. How can I do that?
I am implementing the application with MVC3.

Answer 1

As long as you are using HttpContext.Current you will not be able to test it as Unit Test will not have HttpContext.Current.
Try to use an Interface with method returning string, say ReadUser(). Implement this interface in a class in your application. Use the interface variable whichever class you are using this method in. In that class' default constructor set that interface variable value to 'new' implementer class. Add an overload of the constructor which will take a parameter of type interface and set that parameter to interface variable.
Now in your UnitTest project implement same interface in another class. In this implementation you can now pass whatever mock value you want test.
public interface IReadUserInfo
{ string ReadUser(); }
public class ReadUserInfo: IReadUserInfo
{
public string ReadUser()
{
return HttpContext.Current.Request.Headers["SM_USER"];
}
}
public class UserClass
{
IReadUserInfo userinfo;
public UserClass()
{
userinfo = new ReadUserInfo();
}
public USerClass(IReadUserInfo newuserinfo)
{
userinfo = newuserinfo;
}
}
public class TestReadUserInfo : IReadUSerInfo
{
public string ReadUser()
{ return "testvalue"; }
}
If ReadUser is the only value you are using from Request header, then this approach will solve the problem. However, if you using more values from Request object, you might want to mock entire request object in similar way.