public void All_When_No_Page_Id()
        {
            // arrange
            var serviceMock = new Mock <IRegionService>(MockBehavior.Strict);
            var controller  = new RegionController(serviceMock.Object);

            var serviceResult = new PagedRegionListingServiceModel();

            serviceMock.Setup(s => s.AllRegionsAsync(1, null)).ReturnsAsync(serviceResult);

            // act
            var result = controller.All().Result;

            // assert
            Assert.IsAssignableFrom <ViewResult>(result);
            var model = (result as ViewResult)?.Model;

            Assert.True(model != null);
            Assert.IsAssignableFrom <PagedRegionListingServiceModel>(model);
            Assert.True(model as PagedRegionListingServiceModel == serviceResult);
            serviceMock.VerifyAll();
        }