gistfile1.cs

        private HttpActionContext actionContext;
        private HttpControllerContext controllerContext;
        private UserContextFilter filter;
        private HttpRequestHeaders headers;
        private HttpRequestMessage requestMessage;
        private Mock<IUserContextService> userContextService;
        private Mock<HttpActionDescriptor> actionDescriptor;
        private Mock<HttpParameterDescriptor> parameterDescriptor;

        [SetUp]
        public void Setup()
        {
            userContextService = new Mock<IUserContextService>();

            filter = new UserContextFilter(userContextService.Object);

            actionDescriptor = new Mock<HttpActionDescriptor>();
            parameterDescriptor = new Mock<HttpParameterDescriptor>();
            requestMessage = new HttpRequestMessage();
            controllerContext = new HttpControllerContext();
            actionContext = new HttpActionContext();
            actionContext.ControllerContext = controllerContext;
            actionContext.ActionDescriptor = actionDescriptor.Object;
            actionDescriptor.Setup(x => x.GetParameters()).Returns(new Collection<HttpParameterDescriptor> { parameterDescriptor.Object });
            controllerContext.Request = requestMessage;
            headers = requestMessage.Headers;
            controllerContext.Controller = new TestController();
        }