Trying to find the status of auto-fill-mode in a buffer

[Alexandros Prekates]

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. 

Alexandros