bug#38813: Make comint-tests more robust

["Mattias Engdegård" <mattiase@acm.org>]

30 dec. 2019 kl. 16.20 skrev Michael Albinus <michael.albinus@gmx.de>:

> The usual pattern is (while (accept-process-output proc 0 nil t))
> That's what I do in tramp-tests.el

Thank you, but that only works if inside another loop, and then it is a busy-wait, right?
We don't really have a predicate to tell us when we need to stop waiting, unless we use the test condition for that.
We could do

 (while (accept-process-output proc 0.1 nil t))

which isn't strictly necessary since the test logic guarantees that only two accept-process-output calls should be needed, but it doesn't hurt (much).