Set fake locale for fake HttpContext

I am unit testing some piece of code which behaves differently on different locales. I have created a fake HttpContext but need to set the locale for it and have not been able to. here is how i am creating fake HttpContext:

    public static HttpContext FakeHttpContext(string requestUrl)
    {
        var httpRequest = new HttpRequest("", requestUrl, "");
        var stringWriter = new StringWriter();
        var httpResponce = new HttpResponse(stringWriter);
        var httpContext = new HttpContext(httpRequest, httpResponce);

        var sessionContainer = new HttpSessionStateContainer("id", new SessionStateItemCollection(),
                                                new HttpStaticObjectsCollection(), 10, true,
                                                HttpCookieMode.AutoDetect,
                                                SessionStateMode.InProc, false);

        httpContext.Items["AspSession"] = typeof(HttpSessionState).GetConstructor(
                                    BindingFlags.NonPublic | BindingFlags.Instance,
                                    null, CallingConventions.Standard,
                                    new[] { typeof(HttpSessionStateContainer) },
                                    null)
                            .Invoke(new object[] { sessionContainer });

        return httpContext;
    }