FakeHttpMessageHandler.cs

public class FakeHttpMessageHandler : HttpMessageHandler
    {
        public virtual HttpResponseMessage Send(HttpRequestMessage request)
        {
            throw new NotImplementedException("Now we can setup this method with our mocking framework");
        }

        protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, System.Threading.CancellationToken cancellationToken)
        {
            return Task.FromResult(Send(request));
        }
    }