Unit test a class that has Imported values by MEF

Question

Hi,

I have a a class called "ViewFactory" and this class should deliver the right view

right now it has only one method (and it will grow) which I want to write a unit test against.

the class looks like this...

  public class ViewFactory
{

       [ImportMany(AllowRecomposition=true)]
    IEnumerable<ExportFactory<DependencyObject, IViewMetaData>> Views { get; set; }

    public DependencyObject GetViewByName(string name)
    {
        DependencyObject view = null;

        try
        {
            view = Views.Where(v => v.Metadata.ViewName == name).FirstOrDefault().CreateExport().Value;
            return view;
        }
        catch (Exception ex)
        {

            return view;
        }
    }
}

what I do want is to test my method but don't know how to do it because the List of Views is composed on runtime...

I want to test if I get a view for a valid name and I also want to test if I get null if I have an invalid name

What would be the right way?

Answer 1

You would provide your ViewFactory with a set of ExportFactory<,> values suitable for the particular test. Different tests might have different sets, to allow you to test different things. Basically you're faking the injected dependency.