Unit Testing Silverlight Applications – Mocking

In this post I will explore ability to mock various Silverlight classes in order to enable mocking in your unit tests.  There is a variety of mocking frameworks available, but I will pick one for my testing – Moq.  You can download the framework here,  Once this is done, I need to add some references to my Silverlight unit test project.

Moq requires three assemblies available in the folder where Moq is installed:


If we are mocking view model or another object relying on Prism, we also need to add Prism references


Now we are ready to mock!

Let’s start by doing something simple.  I will mock my view model.  The only property I really want to test is my model property, which in my case exposes list of companies.  TO do so, I just need to setup property getter that contains my model.  The getter will be called when first accessed.  Here is what we have:

[Description("VM Mocking")]
public void TestMocking()
    var vm = new Mock<ICompanyListViewModel>();
    vm.SetupGet(testVM => testVM.CompanyList).
        Returns(new ObservableCollection<Company>(new[] {
            new Company()
                { CompanyID = Guid.NewGuid(), DateAdded = DateTime.Now, CompanyName = "some random company"},
            new Company()
                { CompanyID = Guid.NewGuid(), DateAdded = DateTime.Now.AddDays(-1), CompanyName = "another company"}}));
    Assert.AreEqual(2, vm.Object.CompanyList.Count, "Mocking failed");


I am only mocking view model in this case.  With Moq framework, as it is the case with most mocking frameworks, you are required to have interfaces in order to mock.  In case of RIA Services, this is an issue because client side classes are sealed and do not implement interfaces.  If you are using your own WCF service with custom classes, you can avoid this small issue.  You can also mock events as well.  This is how I would mock property changed event in my view model:

companyVM.SetupGet(testVM => testVM.GetCompaniesCommand).Returns(new DelegateCommand<object>((o) =>
    companyVM.Raise(vm => vm.PropertyChanged += null, new System.ComponentModel.PropertyChangedEventArgs("CompanyList"))));


As you can see, mocking is pretty easy concept, and the web page for Moq has quick start guide to help you get started.  Feel free to use a different mocking framework as well.  In the next post I will show how to unit test user interface using Silverlight unit testing framework.



  1. well thanks a lot… im tyring to learn more about that,i have been using till now (in my company) a unit testing tool from typemock,i guess that its familiar to u guys and im not that pleased with them,so i want to find something better than them…

  2. Just for info

    I had problems when using Moq. I installed Moq using nuget but got the following exception when my code hit the .object property:

    “The type initializer for ‘Moq.Mock`1’ threw an exception”

    The solution after some digging turned out to be that Moq has a dependency on Castle Windsor Core and I need to install it using nuget too.

    Harder work than it should be but all good now.



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