void Ex01()
        {
            When("the valid user id and password are set", () =>
            {
                LoginContent.UserId.Value   = "user";
                LoginContent.Password.Value = "password";

                UserAuthentication.Authenticate(LoginContent.UserId.Value, LoginContent.Password.Value)
                .Returns(UserAuthenticationResult.Succeeded());
            });
            When("to click the login button", () =>
                 AvaloniaController.EventHandlersOf(Controller)
                 .GetBy("LoginButton")
                 .Raise(nameof(Button.Click))
                 );
            Then("the content should be navigated to the UserContent", () =>
            {
                Navigator.Received(1).NavigateTo(Arg.Is <UserContent>(content => content.Id == LoginContent.UserId.Value));
            });
        }
        void Ex05()
        {
            When("the no authenticated user id and password are set", () =>
            {
                LoginContent.UserId.Value   = "user";
                LoginContent.Password.Value = "password";

                UserAuthentication.Authenticate(LoginContent.UserId.Value, LoginContent.Password.Value)
                .Returns(UserAuthenticationResult.Failed());
            });
            When("to click the login button", () =>
                 AvaloniaController.EventHandlersOf(Controller)
                 .GetBy("LoginButton")
                 .Raise(nameof(Button.Click))
                 );
            Then("the content should not be navigated to any contents", () =>
            {
                Navigator.DidNotReceive().NavigateTo(Arg.Any <object>());
            });
            Then("the LoginFailureMessage message should be set", () => LoginContent.Message.Value == Resources.LoginFailureMessage);
        }