[Re-sent to list: my first reply went to Eli Zaretskii only.  Sorry.]
On 8/31/20 8:49 PM, Eli Zaretskii wrote:
>> Cc: 10483@debbugs.gnu.org
>> From: Harald Jörg <haj@posteo.de>
>> Date: Mon, 31 Aug 2020 20:08:06 +0200
>>
>> I was hesitating in this particular case because _if_ this issue ever
>> happens again, then the test just hangs forever.
>>
>> Is there a safeguard against this?
> 
> You could run the test in a subordinate Emacs process, and have the
> parent process wait for it to complete with a timeout.

So be it: My attempt to do this is attached, together with tests
to verify that my loop termination isn't harmful to the function.

As always, a review is welcome. I still haven't much experience
in Elisp.  I haven't found examples to steal from, and also missed
the fork/waitpid stuff which I use for such tasks in Perl.
-- 
Cheers,
haj