After using Automapper to map a ViewModel how and what should I test?

Question

I am attempting to test the Index action of a controller. The action uses AutoMapper to map a domain Customer object to a view model TestCustomer

Answer 1

I would probably separate the coupling between AutoMapper and the controller by introducing an abstraction:

public interface IMapper
{
    TDest Map(TSource source);
}

public CustomerToTestCustomerFormMapper: IMapper
{
    static CustomerToTestCustomerFormMapper()
    {
        // TODO: Configure the mapping rules here
    }

    public TestCustomerForm Map(Customer source)
    {
        return Mapper.Map(source);
    }
}

Next you pass this into the controller:

public HomeController: Controller
{
    private readonly IMapper _customerMapper;
    public HomeController(IMapper customerMapper)
    {
        _customerMapper = customerMapper;
    }

    public ActionResult Index()
    {
        TestCustomerForm cust = _customerMapper.Map(
            _repository.GetCustomerByLogin(CurrentUserLoginName)
        );
        return View(cust);
    }
}

And in your unit test you would use your favorite mocking framework to stub this mapper.