IHTTPActionResult custom response and unit testing with WebApi 2

I have created a class which is as follows

public class Response<T> : IHttpActionResult where T : class
   {
      private readonly T _body;

      ....
      public Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken)
      {
        HttpResponseMessage msg = new HttpResponseMessage();

        switch (_httpStatus)
        {
            case HttpResponseStatus.Ok:
            {
                msg = _request.CreateResponse(HttpStatusCode.OK, _body);
                break;
            }
             case HttpResponseStatus.BadRequest:
            {
                msg = _request.CreateResponse(HttpStatusCode.BadRequest, _body);
                break;
            }
            ...
            return Task.FromResult(msg);

      }
   }

This is my base class for returning IHTTPActionResult in my web api calls. It works well for what i require it for.

I now have some unit tests setup using MSTest.

            // Act
            IHttpActionResult result = controller.Step1();  


            // Assert
            Assert.IsNotNull(result, "Is null when it shouldnt be");
            Assert.IsInstanceOfType(result, typeof(Response<BodyContent<LogingActivityResult>>), "Is not expected IsInstanceOfType");

Both of these Assertions work fine. However i now want to actually get @ the data held within my response and assert that they are ok i.e.: correct values, counts, etc but am having no luck with this. I have tried ALL the various System.Web.Http.Results types such as

var contentResult = result as OkNegotiatedContentResult<Response<BodyContent<LogingActivityResult>>>;

or

var contentResult = result as FormattedContentResult<Response<BodyContent<LogingActivityResult>>>;

but both of these are null when i hover over contentResult variable.

Can anyone lead me in the right direction?

Thanks