Test Method 'X' threw exception: System.InvalidOperationException: Mapper not initialized. Call Initialize with appropriate configuration

Question

Here is the code for the method that I'm developing the unit test for:

public ActionResult ItemsListing()
{
    var itemsList = itemsRepository.GetItems(true);

    if (itemsList.Count() > 0)
    {
        var itemsListVMs = Mapper.Map<IEnumerable<Item>, IEnumerable<itemsListingViewModel>>(itemsList);
        return View(itemsListVMs);
    }
    else
    {
        return RedirectToAction("Home");
    }

}

Following is the code from the mapping configuration file:

public static class MappingConfig
{
    public static void RegisterMaps()
    {
        Mapper.Initialize(config =>
        {
            config.CreateMap<Item, itemsListingViewModel>();
        });
    }
}

And I have initialized mapper in the Application_Start() event of the Global.asax as below:

MappingConfig.RegisterMaps();

Below is the simple test method that I'm trying to run:

[TestMethod]
public void ItemsListing()
{
    HomeController controller = new HomeController();

    ViewResult result = controller.ItemsListing() as ViewResult;

    Assert.IsNotNull(result);
}

It works fine when I simply run the application. But when I try to run the unit test method, it shows the mentioned error message. Can anyone help me to get over this issue? Thanks!

Answer 1

You need to create/register the mappings for your unit tests as well as the Application_Start() is not executed. It is associated with IIS, which is not running during unit tests. You have to manually call the mapping configurations.

[TestClass]
public class HomeControllerTests {
    [ClassInitialize]
    public static void Init(TestContext context) {
        MappingConfig.RegisterMaps();
    }

    [TestMethod]
    public void ItemsListing() {
        HomeController controller = new HomeController();

        ViewResult result = controller.ItemsListing() as ViewResult;

        Assert.IsNotNull(result);
    }
}

In the above test the mapping configuration is done in a method decorated with [ClassInitialize] attribute which

ClassInitializeAttribute Class Identifies a method that contains code that must be used before any of the tests in the test class have run and to allocate resources to be used by the test class.