Testing queueable method which relies on jobId

Question

I've updated my code to do some logic along these lines

1. if no job has been created, create a job using System.enqueueJob(QC) and store it's job id.
2. take a bunch of data and store it in a custom object along with the job id.
3. when the job runs it will query to get the stored data matching the job id.

When I run my test methods however, the job id isn't getting set when I run System.enqueueJob() (I'm checking that using a debug statement right after setting the job Id). When I test manually, the job id is set fine. Is this just something that cannot be done in a test method? Are there other ways to test my code?

Edit: sample code

if(jobId  == null){
           QueueableJob context = new QueueableJob();
           context.isSingletonLogic = true;
           jobId = System.enqueueJob(context);
           System.debug('jobID: ' + jobId);
        }

TestClass

 // Run as User
    System.runAs( user )
    {   
        Trigger_Config__c testCS = TestUtil.getCustomSetting(false,false,false);
        insert testCS;
        Account acc = TestUtil.getAccount();
    }
    System.runAs( userNoPermissions )
    {
        Test.startTest();
        QueueableJob.triggerHelper(actListTest,'Account');
        Test.stopTest();
        List<Custom_Object__c> list = new List<Custom_Object__c>([Select Id from Custom_Object__c]);
        system.assertEquals(0,list.size());
    }