Alexandros Prekates <aprekates@posteo.net> writes:

> C-h f auto-fill-mode says : 
>   ''To check whether the minor mode is
>   enabled in the current buffer, evaluate ‘auto-fill-function’. ''
>
> How do we test that IN a certain buffer ? 
> I evaluated (auto-fill-function) in scratch buffer
> but it gives me nil. 

Right, but the docstring tells you to evaluate `auto-fill-function', not
`(auto-fill-function)'.  Indeed, it is a variable.

Example from my scratch buffer:

--8<---------------cut here---------------start------------->8---
;; This buffer is for text that is not saved, and for Lisp evaluation.
;; To create a file, visit it with ‘C-x C-f’ and enter text in its buffer.

auto-fill-function
do-auto-fill
--8<---------------cut here---------------end--------------->8---

HTH, have a lovely day.
-- 
Arsen Arsenović