trying to modify a test trigger for the Chat Up app as advised in the documentation, and I'm not sure how I should change some of the code to reference a custom object instead of Account.

The sample code is:

 test.startTest();
        insert myOpportunities;
        test.stopTest();
        
        /*there should be 100 posts as you iterated 100 times*/
        List<AccountFeed> chatterPosts = [select id from AccountFeed where parentId = :a.id];
        System.assertEquals(chatterPosts.size(), 100);

 So I modified "AccountFeed" to my custom object "npe03__Recurring_Donation__c"

         test.startTest();
        insert myOpportunities;
        test.stopTest();
        
        /*there should be 100 posts as you iterated 100 times*/
        List<npe03__Recurring_Donation__cFeed> chatterPosts = [select id from npe03__Recurring_Donation__cFeed where parentId = :a.id];
        System.assertEquals(chatterPosts.size(), 100);

and I get this error:

Error: Compile Error: sObject type 'Recurring_Donation__cFeed' is not supported. If you are attempting to use a custom object, be sure to append the '__c' after the entity name. Please reference your WSDL or the describe call for the appropriate names. at line 26 column 56

I've enabled Feed Tracking on the Recurring_Donation__c object (although I haven't selected any other fields to track.  Clearly it's not as simple as replacing "Account" with "npe03__Recurring_Donation__c"

How to fix?

Thanks, Amanda