//[ExpectedException(typeof(ArgumentNullException), "Value cannot be null.")]
        public async Task AuthenticateAsync_ShouldSetPrincipal()
        {
            HttpRequestMessage request = new HttpRequestMessage();
            HttpControllerContext controllerContext = new HttpControllerContext();
            controllerContext.Request = request;
            HttpActionContext context = new HttpActionContext();
            context.ControllerContext = controllerContext;
            HttpAuthenticationContext m = new HttpAuthenticationContext(context, null);
            HttpRequestHeaders headers = request.Headers;
            AuthenticationHeaderValue authorization = new AuthenticationHeaderValue("scheme");
            headers.Authorization = null;
            CancellationToken token = new CancellationToken();

            AnetMerchantAuthenticationAttribute merchantAuth = new AnetMerchantAuthenticationAttribute();
            IPrincipal principal = await AuthenticateAsync("useofforce", "123abc", token);

            Assert.AreEqual(principal.Identity.IsAuthenticated, true);

        }
        public async Task AuthenticateAsync_ShouldReturnForAuthenticationNull()
        {
            HttpRequestMessage request = new HttpRequestMessage();
            HttpControllerContext controllerContext = new HttpControllerContext();
            controllerContext.Request = request;
            HttpActionContext context = new HttpActionContext();
            context.ControllerContext = controllerContext;
            HttpAuthenticationContext m = new HttpAuthenticationContext(context, null);
            HttpRequestHeaders headers = request.Headers;
            AuthenticationHeaderValue authorization = new AuthenticationHeaderValue("scheme");
            headers.Authorization = null;
            CancellationToken token = new CancellationToken();

            AnetMerchantAuthenticationAttribute merchantAuth = new AnetMerchantAuthenticationAttribute();
            IPrincipal principal = await AuthenticateAsync("", "", token);

            Assert.IsNull(principal);

        }