public async Task RegistrationController_GET_Registered_ViewReturned()
        {
            Mock <IClient>         client     = new Mock <IClient>();
            RegistrationController controller = new RegistrationController(client.Object);

            IActionResult actionResult = await controller.Registered(CancellationToken.None);

            ViewResult viewResult = actionResult.ShouldBeOfType <ViewResult>();
        }