How to test big object creation in unit test

Question

I have an apex trigger which fires a platform event. And in the platform event trigger, it creates a big object.

My unit test code is pretty simple and looks like below:

    Account acc = DataFactory.generateSingleAccount();

    Test.startTest();
    insert acc;
    Test.getEventBus().deliver();
    Test.stopTest();

    List<Object_Feed_Store__b> objFeedList = [Select Id, DomainEntityId__c From Object_Feed_Store__b];
    System.assertEquals(1, objFeedList.size());

I checked the code coverage, the platform event trigger is fired successfully, and the below line is successfully executed:

database.insertImmediate(bigObjList);

During normal testing, I have verified the big object is successfully created. But in this scenario, when I query that, the big object is not there. So the assertion failed in my unit test.

I would assume this is due to creation of big object is an asynchronous process even if I have used insertImmediate. But I am not sure how to make that completed in my unit test. Any suggestions?