api in memory tests with facadefactory pattern

I want to integret in memory tests but the problem is that I'm using a facade factory pattern and I have no idea how to configure it.

The problem is that when I make a request, the moment I call a facade method it throws an exception: "Object reference not set to an instance of an object".

As I understood I need to implement the facades in my test configuration, but I have no idea how to do so. I tried googling, but didn't find anything.

My test configuration ATM looks like this:

 [TestFixture]
public class ServerConfiguration : IDisposable
{
    protected HttpServer _httpServer;
    protected const string UrlBase = "http://localhost/";

    [TestFixtureSetUp]
    public void SetupHttpServer()
    {
        var config = new HttpConfiguration();

        config.Routes.MapHttpRoute(
            name: "Carts",
            routeTemplate: "Carts/{id}",
            defaults: new { controller = "Carts" }
        );
        config.IncludeErrorDetailPolicy = IncludeErrorDetailPolicy.Always;

        _httpServer = new HttpServer(config);
    }

        protected HttpRequestMessage createRequest(string url, string mthv, HttpMethod method)
        {
            var request = new HttpRequestMessage();

            request.RequestUri = new Uri(UrlBase + url);
            request.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(mthv));
            request.Method = method;

            return request;
        }

        public void Dispose()
        {
            if (_httpServer != null)
            {
                _httpServer.Dispose();
            }
        }
    }

and my global is:

 protected void Application_Start()
        {
            ...
            ...
            ...
            FacadeFactory.RegisterContainerAccessor(this);
            DataContainer.RegisterContainerAccessor(this);
        }