Different return values the first and second time with Moq

Question

I have a test like this:

    [TestCase("~/page/myaction")]     public void Page_With_Custom_Action(string path) {         // Arrange         var pathData = new Mock<IPathData>();         var pageModel = new Mock<IPageModel>();         var repository = new Mock<IPageRepository>();         var mapper = new Mock<IControllerMapper>();         var container = new Mock<IContainer>();          container.Setup(x => x.GetInstance<IPageRepository>()).Returns(repository.Object);          repository.Setup(x => x.GetPageByUrl<IPageModel>(path)).Returns(() => pageModel.Object);          pathData.Setup(x => x.Action).Returns("myaction");         pathData.Setup(x => x.Controller).Returns("page");          var resolver = new DashboardPathResolver(pathData.Object, repository.Object, mapper.Object, container.Object);          // Act         var data = resolver.ResolvePath(path);          // Assert         Assert.NotNull(data);         Assert.AreEqual("myaction", data.Action);         Assert.AreEqual("page", data.Controller);     } 

GetPageByUrl runs twice in my DashboardPathResolver, how can I tell Moq to return null the first time and pageModel.Object the second?

Answer 1

With the latest version of Moq(4.2.1312.1622), you can setup a sequence of events using SetupSequence. Here's an example:

_mockClient.SetupSequence(m => m.Connect(It.IsAny<String>(), It.IsAny<int>(), It.IsAny<int>()))         .Throws(new SocketException())         .Throws(new SocketException())         .Returns(true)         .Throws(new SocketException())         .Returns(true); 

Calling connect will only be successful on the third and fifth attempt otherwise an exception will be thrown.

So for your example it would just be something like:

repository.SetupSequence(x => x.GetPageByUrl<IPageModel>(virtualUrl)) .Returns(null) .Returns(pageModel.Object); 

Answer 2

The existing answers are great, but I thought I'd throw in my alternative which just uses System.Collections.Generic.Queue and doesn't require any special knowledge of the mocking framework - since I didn't have any when I wrote it! :)

var pageModel = new Mock<IPageModel>(); IPageModel pageModelNull = null; var pageModels = new Queue<IPageModel>(); pageModels.Enqueue(pageModelNull); pageModels.Enqueue(pageModel.Object); 

Then...

repository.Setup(x => x.GetPageByUrl<IPageModel>(path)).Returns(pageModels.Dequeue);