bug#56773: 29.0.50; (readablep UNREADABLE) causes strange things

[Lars Ingebrigtsen <larsi@gnus.org>]

Po Lu <luangruo@yahoo.com> writes:

> I didn't see one, but the spam filter is rather agressive these days, so
> it would be nice for you to send it again in reply to this message.

Test terpri backtrace:
  signal(ert-test-failed (((should (string= (with-current-buffer (mark
  ert-fail(((should (string= (with-current-buffer (marker-buffer stand
  (if (unwind-protect (setq value-197 (apply fn-195 args-196)) (setq f
  (let (form-description-199) (if (unwind-protect (setq value-197 (app
  (let ((value-197 'ert-form-evaluation-aborted-198)) (let (form-descr
  (let* ((fn-195 #'string=) (args-196 (condition-case err (let ((signa
  (let ((standard-output (save-current-buffer (set-buffer (get-buffer-
  (closure (t) nil (let* ((fn-135 #'string=) (args-136 (condition-case
  ert--run-test-internal(#s(ert--test-execution-info :test #s(ert-test
  ert-run-test(#s(ert-test :name terpri :documentation nil :body (clos
  ert-run-or-rerun-test(#s(ert--stats :selector ... :tests ... :test-m
  ert-run-tests((not (or (tag :expensive-test) (tag :unstable))) #f(co
  ert-run-tests-batch((not (or (tag :expensive-test) (tag :unstable)))
  ert-run-tests-batch-and-exit((not (or (tag :expensive-test) (tag :un
  eval((ert-run-tests-batch-and-exit '(not (or (tag :expensive-test) (
  command-line-1(("-L" ":." "-l" "ert" "-l" "src/print-tests.el" "--ev
  command-line()
  normal-top-level()
Test terpri condition:
    (ert-test-failed
     ((should
       (string=
	(with-current-buffer ... ...)
	"--------\n"))
      :form
      (string= "" "--------\n")
      :value nil :explanation
      (arrays-of-different-length 0 9 "" "--------\n" first-mismatch-at 0)))
   FAILED  41/45  terpri (0.000117 sec) at src/print-tests.el:110
   passed  42/45  test-dots (0.000062 sec)
   passed  43/45  test-prin1-overrides (0.000066 sec)
   passed  44/45  test-prin1-to-string-overrides (0.000049 sec)
   passed  45/45  test-unreadable (0.000029 sec)

Ran 45 tests, 44 results as expected, 1 unexpected (2022-07-28 13:08:34+0200, 0.132581 sec)
3 expected failures

1 unexpected results:
   FAILED  terpri