I'm trying to create feedpollchoice record in test class but it's throwing exception as fields not writable although i have pernission.pls help on this thanks

Hi,
I have a trigger and a class which implements a queueable interface.
When a record gets created the trigger invokes the queueable interface which will make a callout.

Now I'm writing the test class for the same.
In the test class I'm setting the mock response using httpMockCallout and inserting the record.
But I'm getting an exception, Callout loop not allowed.
Any Idea why this is happening?

As a workaround I set the response using test.Isrunningtest and it works fine.

Any pointers would be helpful.
Many Thanks