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+;;; test-music-config--playlist-dock.el --- Tests for the F10 playlist dock -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; The F10 playlist always docks at the bottom, whatever the frame's shape.
+;; It used to pick `right' on a wide frame via `cj/preferred-dock-direction',
+;; which produced an unwanted three-way split on a wide terminal.
+;;
+;; `cj/side-window-display' is the window-system boundary here, so it is the
+;; thing stubbed (an ordinary defun -- safe to `cl-letf', unlike the frame-*
+;; subrs).  Stubbing it lets these tests assert what the toggle *asks for*
+;; without needing a live frame under `--batch'.
+
+;;; Code:
+
+(require 'ert)
+(require 'cl-lib)
+
+(add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+(require 'music-config)
+
+(defmacro test-music-dock--with-captured-side (captured &rest body)
+  "Run BODY with the playlist display path stubbed, recording its args in CAPTURED.
+CAPTURED is set to a plist of :side, :size-var and :default-size."
+  (declare (indent 1))
+  `(let ((buffer (generate-new-buffer " *test-playlist*")))
+     (unwind-protect
+         (cl-letf (((symbol-function 'cj/emms--setup) (lambda (&rest _) nil))
+                   ((symbol-function 'cj/music--ensure-playlist-buffer)
+                    (lambda (&rest _) buffer))
+                   ((symbol-function 'emms-playlist-mode-center-current)
+                    (lambda (&rest _) nil))
+                   ((symbol-function 'cj/side-window-display)
+                    (lambda (_buf side size-var default-size)
+                      (setq ,captured (list :side side :size-var size-var
+                                            :default-size default-size))
+                      (selected-window))))
+           ,@body)
+       (kill-buffer buffer))))
+
+(ert-deftest test-music-config-playlist-toggle-docks-bottom-on-wide-frame ()
+  "Normal: a wide frame still docks the playlist at the bottom.
+A wide frame used to dock right, splitting the frame three ways."
+  (let (captured)
+    (test-music-dock--with-captured-side captured
+      (cl-letf (((symbol-function 'frame-width) (lambda (&rest _) 400)))
+        (cj/music-playlist-toggle)))
+    (should (eq 'bottom (plist-get captured :side)))))
+
+(ert-deftest test-music-config-playlist-toggle-docks-bottom-on-narrow-frame ()
+  "Boundary: a narrow frame docks at the bottom, as it always did."
+  (let (captured)
+    (test-music-dock--with-captured-side captured
+      (cl-letf (((symbol-function 'frame-width) (lambda (&rest _) 40)))
+        (cj/music-playlist-toggle)))
+    (should (eq 'bottom (plist-get captured :side)))))
+
+(ert-deftest test-music-config-playlist-toggle-uses-height-memory ()
+  "Normal: the bottom dock carries the height fraction and its memory var."
+  (let (captured)
+    (test-music-dock--with-captured-side captured
+      (cj/music-playlist-toggle))
+    (should (eq 'cj/--music-playlist-height (plist-get captured :size-var)))
+    (should (= cj/music-playlist-window-height (plist-get captured :default-size)))))
+
+(ert-deftest test-music-config-playlist-dock-has-no-width-knobs ()
+  "Error: the right-dock width variables are gone, not merely unused.
+A stale `cj/music-playlist-window-width' would read as a live knob that
+silently does nothing."
+  (should-not (boundp 'cj/music-playlist-window-width))
+  (should-not (boundp 'cj/--music-playlist-width))
+  (should-not (fboundp 'cj/--music-playlist-side)))
+
+(ert-deftest test-music-config-playlist-default-height-is-half ()
+  "Normal: the dock opens at half the frame height by default (Craig,
+2026-07-18 -- a third still read too short for a real playlist)."
+  (should (= cj/music-playlist-window-height 0.5)))
+
+(ert-deftest test-music-config-playlist-toggle-off-discards-shrunk-height ()
+  "Error: a captured height below the default is discarded.  Window churn
+squeezes the dock, and remembering the squeeze reopens it too short on
+every later toggle."
+  (let ((buffer (generate-new-buffer " *test-playlist-shrink*"))
+        (cj/--music-playlist-height nil))
+    (unwind-protect
+        (save-window-excursion
+          (set-window-buffer (selected-window) buffer)
+          (let ((cj/music-playlist-buffer-name (buffer-name buffer)))
+            (cl-letf (((symbol-function 'cj/side-window-capture-size)
+                       (lambda (_w _side var) (set var 0.2)))
+                      ((symbol-function 'delete-window) #'ignore)
+                      ((symbol-function 'message) #'ignore))
+              (cj/music-playlist-toggle)))
+          (should (null cj/--music-playlist-height)))
+      (kill-buffer buffer))))
+
+(ert-deftest test-music-config-playlist-toggle-off-keeps-enlarged-height ()
+  "Normal: a captured height at or above the default is remembered, so a
+deliberate enlargement sticks for the session."
+  (let ((buffer (generate-new-buffer " *test-playlist-grow*"))
+        (cj/--music-playlist-height nil))
+    (unwind-protect
+        (save-window-excursion
+          (set-window-buffer (selected-window) buffer)
+          (let ((cj/music-playlist-buffer-name (buffer-name buffer)))
+            (cl-letf (((symbol-function 'cj/side-window-capture-size)
+                       (lambda (_w _side var) (set var 0.5)))
+                      ((symbol-function 'delete-window) #'ignore)
+                      ((symbol-function 'message) #'ignore))
+              (cj/music-playlist-toggle)))
+          (should (= 0.5 cj/--music-playlist-height)))
+      (kill-buffer buffer))))
+
+(provide 'test-music-config--playlist-dock)
+;;; test-music-config--playlist-dock.el ends here