bug#51037: [PATCH] Make `print-level` & `print-length` customizable in ERT batch tests

[Michael]

Lars Ingebrigtsen <larsi@gnus.org> writes:

> Michael <sp1ff@runbox.com> writes:
>
> > When running ERT tests in batch mode, the conservative values
> > chosen for `print-level` and `print-length` sometimes make it
> > difficult to see what exactly is wrong.  This patch introduces
> > two new variables (`ert-batch-print-level` &
> > `ert-batch-print-length`) that one can use to customize them;
> > e.g.
> >
> >    emacs -batch -l ert -l my-tests.el \
> >          --eval "(let ((ert-batch-print-level 10) \
> >                        (ert-batch-print-length 120)) \
> >                    (ert-run-tests-batch-and-exit))"
>
> Sounds like a good idea.
>
> > +MESSAGE-FN should normally be nil; it is used for automated
> > +self-tests and specify how to display messages."
>
> I don't understand this bit, though.  If you want to test how 
> this
> function outputs messages, you can just `cl-letf' like this:
>
> (cl-letf (((symbol-function 'message) ...

Good point. I simply carried the strategy over from that used to
unit test `ert-run-tests-interactively`. TBH I was unaware of
`cl-letf`, and there *is* this comment above
`ert-run-tests-interactively`:

   ;; Should OUTPUT-BUFFER-NAME and MESSAGE-FN really be 
   arguments here?
   ;; They are needed only for our automated self-tests at the 
   moment.
   ;; Or should there be some other mechanism?

Perhaps I should change *both* to just use `cl-letf`?

--
Michael <sp1ff@runbox.com>