public async Task AuthHandler_Selects_UsernamePassword()
        {
            string username     = "******";
            string password     = "******";
            var    expectedAuth = AuthenticationHandler.EncodeCredentials(username, password);

            var handler = new AuthenticationHandler(null, null, NullLogger.Instance);

            handler.SetCredentials(username, password);

            var fakeHandler = new FakeRequireAuthHandler("Basic", null, expectedAuth);

            handler.InnerHandler = fakeHandler;

            var invoker  = new HttpMessageInvoker(handler);
            var response = await invoker.SendAsync(new HttpRequestMessage(), CancellationToken.None);

            response.EnsureSuccessStatusCode();
        }