HttpListenerRequest to HttpRequestBase

I am using some DNOA code in my service that requires a HttpRequestBase.
So I am converting the IRequest.OriginalRequest to `HttpRequestBase’ like this:

var requestBase = (HttpRequestBase)request.OriginalRequest;

In integration testing, I am hosting my code within a AppSelfHostBase service.
So during this testing, the request.OriginalRequest is of type HttpListerRequest, not HttpRequestBase and DNOA barfs big time. That’s because I am not running in ASP.NET during testing.
Surely there is a trick here, that can be put in place just for testing.

How do I get an instance of HttpRequestBase during this kind of testing?

The DNOA API will also accept a HttpRequestMessage instead of HttpRequestBase, I guess I could manufacture one of those from IRequest then.

DNOA is tied to and only works with ASP.NET Hosts.