Question

I wish to use unit testing in a project that I am involved in. The solution has a UI layer, a Domain Logic Layer and Database base all seperated into physically seperated dlls, so it is pretty standard nowdays.

In the Domain layer we have a class that makes use of

new HttpContextWrapper(HttpContext.Current)

to get the context of the current request to compile a Url for dynamic menus. And as expected everything works fine when running in a web environment as this HttpContext.Current is always set.

However when I come to unit test a controller I hit this line of code and get a Null reference exception.

After some research I have many articles that suggest using Mock to create a Fake Http Context and set this when creating the controller like so:

var httpContext = FakeHttpContext();
ControllerContext context = new ControllerContext(new RequestContext(httpContext, new RouteData()), controller);
controller.ControllerContext = context;

But this still does not change the HttpContxt.Current and I am still getting a null reference exception.

What am I doing wrong / How can I resolve this exception?

Answer 1

You can’t use HttpContext.Current in this way. At one of my previous gigs, in order to account for this, we had to create a separate wrapper class and access that property.

Using statics is a very common problem in unit testing.

Per your request for an update:

public static class HttpContextContainer
{
     private static HttpContext _ctx;
     public static HttpContext Current 
     {
         get 
         { 
             if (_ctx == null) _ctx = HttpContext.Current;
             return _ctx;
         }
         set
         {
             _ctx = value;
         }
     }
}

Then in your usage you might do something like:

new HttpContextWrapper(HttpContextContainer.Current)

and:

var httpContext = FakeHttpContext();
HttpContextContainer.Current = httpContext;
ControllerContext context = new ControllerContext(new RequestContext(httpContext, new RouteData()), controller);
controller.ControllerContext = context;