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diff --git a/test/lisp/erc/erc-scenarios-keep-place-indicator.el b/test/lisp/erc/erc-scenarios-keep-place-indicator.el
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+;;; erc-scenarios-keep-place-indicator.el --- erc-keep-place-indicator-mode -*- lexical-binding: t -*-
+
+;; Copyright (C) 2023-2024 Free Software Foundation, Inc.
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.
+
+;;; Code:
+
+(require 'ert-x)
+(eval-and-compile
+  (let ((load-path (cons (ert-resource-directory) load-path)))
+    (require 'erc-scenarios-common)))
+
+(require 'erc-goodies)
+
+;; This test shows that the indicator does not update when at least
+;; one window remains.  When the last window showing a buffer switches
+;; away, the indicator is updated if it's earlier in the buffer.
+(ert-deftest erc-scenarios-keep-place-indicator--follow ()
+  :tags `(:expensive-test
+          ,@(and (getenv "ERC_TESTS_GRAPHICAL") '(:erc--graphical)))
+  (when (version< emacs-version "29") (ert-skip "Times out"))
+  ;; XXX verify that this continues to be the case ^.
+
+  (should-not erc-scrolltobottom-all)
+  (should-not erc-scrolltobottom-mode)
+  (should-not erc-keep-place-mode)
+
+  (erc-scenarios-common-with-noninteractive-in-term
+      ((erc-scenarios-common-dialog "keep-place")
+       (dumb-server (erc-d-run "localhost" t 'follow))
+       (port (process-contact dumb-server :service))
+       (erc-modules `( keep-place-indicator scrolltobottom fill-wrap
+                       ,@erc-modules))
+       (erc-keep-place-indicator-follow t)
+       (erc-scrolltobottom-all t)
+       (erc-server-flood-penalty 0.1)
+       (erc-autojoin-channels-alist '((foonet "#chan" "#spam")))
+       (expect (erc-d-t-make-expecter)))
+
+    (ert-info ("Connect")
+      (with-current-buffer (erc :server "127.0.0.1"
+                                :port port
+                                :full-name "tester"
+                                :nick "tester"
+                                :user "tester")
+        (funcall expect 10 "debug mode")))
+
+    (with-current-buffer (erc-d-t-wait-for 10 (get-buffer "#chan"))
+      (set-window-buffer nil (current-buffer))
+      (delete-other-windows)
+      (split-window-below)
+      (funcall expect 10 "<bob> tester, welcome!")
+      (recenter 0)
+      (other-window 1)
+      (funcall expect 10 "<alice> tester, welcome!")
+      (recenter 0)
+      (should (= 2 (length (window-list))))
+
+      (ert-info ("Last window to switch away has point earlier in buffer")
+        ;; Lower window, with point later in buffer, switches away first.
+        (switch-to-buffer (erc-d-t-wait-for 10 (get-buffer "#spam"))) ; lower
+        (other-window 1)
+        (switch-to-buffer "#spam") ; upper
+        (erc-scenarios-common-say "one")
+        (funcall expect 10 "Ay, the heads")
+
+        ;; Overlay has moved to upper window start.
+        (switch-to-buffer "#chan")
+        (redisplay) ; force overlay to update
+        (save-excursion
+          (goto-char (window-point))
+          (should (looking-back (rx "<bob> tester, welcome!")))
+          (should (= (pos-bol) (window-start)))
+          (erc-d-t-wait-for 20
+              (= (overlay-start erc--keep-place-indicator-overlay) (pos-bol))))
+        ;; Lower window is still centered at start.
+        (other-window 1)
+        (switch-to-buffer "#chan")
+        (save-excursion
+          (goto-char (window-point))
+          (should (looking-back (rx "<alice> tester, welcome!")))
+          (should (= (pos-bol) (window-start)))))
+
+      (ert-info ("Last window to switch away has point later in buffer")
+        ;; Lower window advances.
+        (funcall expect 10 "<bob> alice: Since you can cog")
+        (recenter 0)
+        (redisplay) ; force ^ to appear on first line
+
+        (other-window 1) ; upper still at indicator, switches first
+        (switch-to-buffer "#spam")
+        (other-window 1)
+        (switch-to-buffer "#spam") ; lower follows, speaks to sync
+        (erc-scenarios-common-say "two")
+        (funcall expect 10 "<bob> Cause they take")
+        (goto-char (point-max))
+
+        ;; Upper switches back first, finds indicator gone.
+        (other-window 1)
+        (switch-to-buffer "#chan")
+        (save-excursion
+          (goto-char (window-point))
+          (should (looking-back (rx "<bob> tester, welcome!")))
+          (should (= (pos-bol) (window-start)))
+          (should (> (overlay-start erc--keep-place-indicator-overlay)
+                     (pos-eol))))
+
+        ;; Lower window follows, window-start preserved.
+        (other-window 1)
+        (switch-to-buffer "#chan")
+        (save-excursion
+          (goto-char (window-point))
+          (should (looking-back (rx "you can cog")))
+          (should (= (pos-bol) (window-start)))
+          (should (= (overlay-start erc--keep-place-indicator-overlay)
+                     (pos-bol)))))
+
+      (ert-info ("description")
+        (erc-send-input-line "#spam" "three")
+        (save-excursion (erc-d-t-search-for 10 "Ready"))
+        (switch-to-buffer "#spam")
+        (should (< (point) erc-input-marker))))
+
+    (erc-keep-place-mode -1)
+    (erc-scrolltobottom-mode -1)))
+
+;;; erc-scenarios-keep-place-indicator.el ends here