How to mole the GetEnumerator method for SPJobDefinitionCollection

Question

Can somebody help me please?

I need create a unit test using moles for this method:

   public override void FeatureActivated(SPFeatureReceiverProperties properties)
    {
        SPWebApplication webApp = properties.Feature.Parent as SPWebApplication;
        foreach (SPJobDefinition job in webApp.JobDefinitions)
            if (job.Name == "AAAA") job.Delete();
        AssistantJob aJob = new AssistantJob(webApp);
        SPDailySchedule schedule = new SPDailySchedule();
        schedule.BeginHour = 2;
        schedule.BeginMinute = 30;
        schedule.BeginSecond = 0;
        schedule.EndHour = 3;
        schedule.EndMinute = 30;
        schedule.EndSecond = 0;
        aJob.Schedule = schedule;
        aJob.Update();
    }

But, when I execute the test the following error message appears:

failing test: MoleNotImplementedException, SPPersistedObjectCollection`1.GetEnumerator() was not moled.

This error occur in this line:

        foreach (SPJobDefinition job in webApp.JobDefinitions)

This is my unit test code:

    [PexMethod]
    public void FeatureActivated(
        [PexAssumeUnderTest]ApprovalAssistantCleanupEventReceiver target
    )
    {
        MSPFarm.BehaveAsNotImplemented();

        BSPFeatureReceiverProperties props = new BSPFeatureReceiverProperties();
        BSPFeature feature = new BSPFeature();
        MSPWebApplication webapp = new MSPWebApplication();

        props.Feature = feature;
        feature.Parent = webapp.Instance;
        webapp.JobDefinitionsGet = () => new MSPJobDefinitionCollection();

        target.FeatureActivated(props);

    }

I've read on the internet I need use Binding to implement GetEnumerator() into a collection. Then changed my unit test to implement this, but the error is the same. The AssistantJob class implement the JobDefinition abstract class.

        webapp.JobDefinitionsGet = () => new MSPJobDefinitionCollection().Bind(new MApprovalAssistantJob[] {
            new MAssistantJob() {  },
            new MAssistantJob() {  }
        });

Can someone help me to add MAssistantJob items inside the MSPJobDefinitionCollection???

I'm sorry my English isn't good.

Thanks very much.