diff --git a/ci/simple-tests/README.md b/ci/simple-tests/README.md
index c949d58d7..523975c6e 100644
--- a/ci/simple-tests/README.md
+++ b/ci/simple-tests/README.md
@@ -15,6 +15,9 @@ coq-test-prelude-correct
 coq-test-goals-present
 : test that Proof General shows goals correctly in various
   situations
+coq-test-three-window.el
+: Test three-pane mode for different frame sizes, including ones that
+  are too small for three windows.
 
 # Overview of existing tests for qRHL
 
diff --git a/ci/simple-tests/coq-test-three-window.el b/ci/simple-tests/coq-test-three-window.el
new file mode 100644
index 000000000..972bb1f68
--- /dev/null
+++ b/ci/simple-tests/coq-test-three-window.el
@@ -0,0 +1,121 @@
+;; This file is part of Proof General.
+;; 
+;; © Copyright 2024  Hendrik Tews
+;; 
+;; Authors: Hendrik Tews
+;; Maintainer: Hendrik Tews <hendrik@askra.de>
+;; 
+;; License:     GPL (GNU GENERAL PUBLIC LICENSE)
+
+;;; Commentary:
+;;
+;; Starting Proof General in three-pane mode
+;; (`proof-three-window-enable' is t and
+;; `proof-three-window-mode-policy' is 'smart) used to fail with
+;; "window ... too small for splitting" for frame heights less then
+;; three times `window-min-height' (which defaults to 4). The problem
+;; was relevant for Emacs 26.3, 27.1, and 27.2 running in batch mode
+;; in docker containers, because they set their frame height to 9 (and
+;; their width to 10). For this reason most Proof General CI tests
+;; disable three pane mode in one or the other way.
+;;
+;; This file tests the internal function `proof-select-three-b' that
+;; contains the bug and one user command affected by the bug
+;; (`proof-toggle-active-scripting') with three different frame sizes:
+;; too small for 3 windows, just big enough for 3 windows, and the
+;; default frame size. 
+
+(require 'pg-response)
+
+(defun reset-coq ()
+  "Reset Coq and Proof General.
+Do `proof-shell-exit' to kill Coq and reset the locked region and
+a lot of other internal state of Proof General. Used at the
+beginning of the test when several tests work on the same Coq
+source file."
+  (when (and (boundp 'proof-shell-buffer)
+             (buffer-live-p proof-shell-buffer))
+    (proof-shell-exit t)
+    (message "Coq and Proof General reseted")))
+
+
+(defun test-proof-select-three-b-for-height (height)
+  "Test `proof-select-three-b' in 3-pane mode for HEIGHT.
+The function should not signal an error and set up 3 windows."
+  (let ((b1 (get-buffer-create "test-b1"))
+        (b2 (get-buffer-create "test-b2"))
+        (b3 (get-buffer-create "test-b3"))
+        ;; the following is set to its default value
+        (proof-three-window-enable t))
+    (reset-coq)
+    (message "Check test-proof-select-three-b for height %d" height)
+    (set-frame-height (selected-frame) height)
+    (proof-select-three-b b1 b2 b3 'smart)
+    (message "Apparently no error signaled in proof-select-three-b")
+    (message "Check that there are 3 windows")
+    (should (eq (length (window-list)) 3))))
+
+(ert-deftest test-proof-select-three-b-too-small ()
+  "Test `proof-select-three-b' for a frame height too small for 3 windows."
+  :expected-result :failed
+  (test-proof-select-three-b-for-height (- (* 3 window-min-height) 1)))
+          
+(ert-deftest test-proof-select-three-b-just-big-enough ()
+  "Test `proof-select-three-b' for a frame height just big enough for 3 windows."
+  (test-proof-select-three-b-for-height (* 3 window-min-height)))
+          
+(ert-deftest test-proof-select-three-b-default-height ()
+  "Test `proof-select-three-b' for the default frame height.
+Note that for Emacs 26.3, 27.1, and 27.2, the default frame
+height is 9 when running in a docker container."
+  :expected-result (if (and
+                        ;; >= 26.3
+                        (or (> emacs-major-version 26)
+                            (and (eq emacs-major-version 26)
+                                 (>= emacs-minor-version 3)))
+                        ;; < 28
+                        (< emacs-major-version 28))
+                       :failed
+                     :passed)
+  (test-proof-select-three-b-for-height (frame-height)))
+
+
+(defun test-activate-scripting-for-height (height)
+  "Test `proof-toggle-active-scripting' in 3-pane mode for HEIGHT.
+The function should not signal an error and there should be 3
+windows afterwards."
+  (let ((proof-three-window-enable t)
+        (proof-three-window-mode-policy 'smart))
+    (reset-coq)
+    (message "Check proof-toggle-active-scripting for height %d" height)
+    (set-frame-height (selected-frame) height)
+    (find-file "some_file.v")
+    (proof-toggle-active-scripting)
+    (message "Apparently no error signaled in proof-toggle-active-scripting")
+    (message "Check that there are 3 windows")
+    (should (eq (length (window-list)) 3))))
+
+
+(ert-deftest test-proof-toggle-active-scripting-too-small ()
+  "Test `proof-toggle-active-scripting' in a frame too small for 3 windows."
+  :expected-result :failed
+  (test-activate-scripting-for-height (- (* 3 window-min-height) 1)))
+
+(ert-deftest test-proof-toggle-active-scripting-just-big-enough ()
+  "Test `proof-toggle-active-scripting' in a frame just enough for 3 windows."
+    (test-activate-scripting-for-height (* 3 window-min-height)))
+
+(ert-deftest test-proof-toggle-active-scripting-default-height ()
+  "Test `proof-toggle-active-scripting' with the default frame size.
+Note that for Emacs 26.3, 27.1, and 27.2, the default frame
+height is 9 when running in a docker container."
+  :expected-result (if (and
+                        ;; >= 26.3
+                        (or (> emacs-major-version 26)
+                            (and (eq emacs-major-version 26)
+                                 (>= emacs-minor-version 3)))
+                        ;; < 28
+                        (< emacs-major-version 28))
+                       :failed
+                     :passed)
+  (test-activate-scripting-for-height (frame-height)))