Unit testing RedirectToAction in controller MVC5.

BlogController.cs

 public class BlogController : Controller
    {
        private IArticleRepository ArticleData { get; set; }
        private IUserRepository UserRepository { get; set; }

        public BlogController(IArticleRepository articleRepository, IUserRepository userRepository)
        {
            if(articleRepository == null) throw new ArgumentNullException("articleRepository");
            if (userRepository == null) throw new ArgumentNullException("userRepository");

            ArticleData = articleRepository;
            UserRepository = userRepository;
        }
        
        public ActionResult Index()
        {
            return View();
        }
        
        public ActionResult Detail(int year, int month, string title)
        {
            var article = ArticleData.GetArticle(year, month, title);
            
            if (article == null) return RedirectToAction("Index", "Blog");

            var model = new TestModel();
            
            return View(model);
        }
    }

BlogControllerTests.cs

using System.Collections.Generic;
using System.Linq;
using blog.Controllers;
using Blog.Core.Entities;
using Blog.Core.Intefaces;
using blog.Models.Blog;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System.Web.Mvc;
using Moq;

namespace blog.Tests.Controllers
{
    [TestClass]
    public class BlogControllerTest
    {
        private Mock<IArticleRepository> _articleRepository;
        private Mock<IUserRepository> _userRepository;

        [TestInitialize]
        public void Init()
        {
            _articleRepository = new Mock<IArticleRepository>();
            _userRepository = new Mock<IUserRepository>();
        }

        [TestMethod]
        public void BlogControllerIndex()
        {
            // Assign
            var list = new List<Article>();

            // Mock
            _articleRepository.Setup(x => x.GetArticlesForYearMonth(It.IsAny<int>(), It.IsAny<int>()))
                              .Returns(list);

            // Arrange
            var controller = new BlogController(_articleRepository.Object, _userRepository.Object);

            // Act
            var result = controller.Index() as ViewResult;
            var model = result.Model as BlogModel;

            // Assert
            Assert.AreEqual(list.Count(), model.Articles.Count());
        }

        [TestMethod]
        public void BlogControllerDetailWhenNullRedirectsToIndex()
        {
            // Assign
            Article article = null;

            // Mock
            _articleRepository.Setup(x => x.GetArticle(It.IsAny<int>(), It.IsAny<int>(), It.IsAny<string>))
                              .Returns(article);

            // Arrange
            var controller = new BlogController(_articleRepository.Object, _userRepository.Object);

            // Act
            var result = (RedirectToRouteResult)controller.Detail(1,1,"test");

            // Assert
            Assert.AreEqual("Index", result.RouteValues["action"]);
            Assert.AreEqual("Blog",  result.RouteValues["controller"]);
        }
    }
}