feat(music): add test coverage for 7 functions, refactor with extracted helpersHEADmain

Add 47 new unit tests across 7 test files covering playlist-modified-p,
assert-valid-playlist-file, playlist-tracks, create-radio-station,
ensure-playlist-buffer, after-playlist-clear, and header-text.

Extract three helpers to reduce duplication: assert-m3u-files-exist (dedupes
2 identical guards), sync-playlist-file (dedupes 3 state-sync patterns),
and select-m3u-file (reusable M3U selection with cancel). Simplify
append-track-to-playlist nesting from 6 to 4 levels. Delete unused
cj/music-keymap-prefix variable.

1 files changed, 156 insertions, 0 deletions

diff --git a/tests/test-music-config--header-text.el b/tests/test-music-config--header-text.el
new file mode 100644
index 00000000..8de97350
--- /dev/null
+++ b/tests/test-music-config--header-text.el
@@ -0,0 +1,156 @@
+;;; test-music-config--header-text.el --- Tests for playlist header string generation -*- coding: utf-8; lexical-binding: t; -*-
+;;
+;; Author: Craig Jennings <c@cjennings.net>
+;;
+;;; Commentary:
+;; Unit tests for cj/music--header-text function.
+;; Tests the multi-line header string builder for the playlist overlay.
+;;
+;; Test organization:
+;; - Normal Cases: Playlist name from file, "Untitled" default, track count
+;; - Boundary Cases: Stopped state, paused state, mode indicators
+;; - Error Cases: Empty playlist buffer
+;;
+;;; Code:
+
+(require 'ert)
+
+;; Stub missing dependencies before loading music-config
+(defvar-keymap cj/custom-keymap
+  :doc "Stub keymap for testing")
+
+;; Add EMMS elpa directory to load path for batch testing
+(let ((emms-dir (car (file-expand-wildcards
+                      (expand-file-name "elpa/emms-*" user-emacs-directory)))))
+  (when emms-dir
+    (add-to-list 'load-path emms-dir)))
+
+(require 'emms)
+(require 'emms-playlist-mode)
+(require 'music-config)
+
+;;; Test helpers
+
+(defun test-header--setup-playlist-buffer (track-names)
+  "Create an EMMS playlist buffer with TRACK-NAMES and return it."
+  (let ((buf (get-buffer-create cj/music-playlist-buffer-name)))
+    (with-current-buffer buf
+      (emms-playlist-mode)
+      (setq emms-playlist-buffer-p t)
+      (let ((inhibit-read-only t))
+        (erase-buffer)
+        (dolist (name track-names)
+          (emms-playlist-insert-track (emms-track 'file name)))))
+    (setq emms-playlist-buffer buf)
+    buf))
+
+(defun test-header--teardown ()
+  "Clean up test playlist buffer and reset EMMS state."
+  (setq emms-player-playing-p nil)
+  (setq emms-player-paused-p nil)
+  (when-let ((buf (get-buffer cj/music-playlist-buffer-name)))
+    (with-current-buffer buf
+      (setq cj/music-playlist-file nil))
+    (kill-buffer buf)))
+
+(defun test-header--strip-properties (str)
+  "Return STR with all text properties removed."
+  (let ((s (copy-sequence str)))
+    (set-text-properties 0 (length s) nil s)
+    s))
+
+;;; Normal Cases
+
+(ert-deftest test-music-config--header-text-normal-shows-playlist-name-from-file ()
+  "Header shows playlist name derived from cj/music-playlist-file."
+  (unwind-protect
+      (progn
+        (test-header--setup-playlist-buffer '("/music/a.mp3"))
+        (with-current-buffer cj/music-playlist-buffer-name
+          (setq cj/music-playlist-file "/path/to/my-jazz.m3u"))
+        (let* ((header (with-current-buffer cj/music-playlist-buffer-name
+                         (cj/music--header-text)))
+               (plain (test-header--strip-properties header)))
+          (should (string-match-p "my-jazz" plain))))
+    (test-header--teardown)))
+
+(ert-deftest test-music-config--header-text-normal-shows-untitled-when-no-file ()
+  "Header shows 'Untitled' when no playlist file is associated."
+  (unwind-protect
+      (progn
+        (test-header--setup-playlist-buffer '("/music/a.mp3"))
+        (with-current-buffer cj/music-playlist-buffer-name
+          (setq cj/music-playlist-file nil))
+        (let* ((header (with-current-buffer cj/music-playlist-buffer-name
+                         (cj/music--header-text)))
+               (plain (test-header--strip-properties header)))
+          (should (string-match-p "Untitled" plain))))
+    (test-header--teardown)))
+
+(ert-deftest test-music-config--header-text-normal-shows-track-count ()
+  "Header shows correct track count."
+  (unwind-protect
+      (progn
+        (test-header--setup-playlist-buffer '("/music/a.mp3" "/music/b.mp3" "/music/c.mp3"))
+        (let* ((header (with-current-buffer cj/music-playlist-buffer-name
+                         (cj/music--header-text)))
+               (plain (test-header--strip-properties header)))
+          (should (string-match-p "(3)" plain))))
+    (test-header--teardown)))
+
+;;; Boundary Cases
+
+(ert-deftest test-music-config--header-text-boundary-stopped-state ()
+  "Header shows 'Stopped' when not playing."
+  (unwind-protect
+      (progn
+        (test-header--setup-playlist-buffer '("/music/a.mp3"))
+        (setq emms-player-playing-p nil)
+        (let* ((header (with-current-buffer cj/music-playlist-buffer-name
+                         (cj/music--header-text)))
+               (plain (test-header--strip-properties header)))
+          (should (string-match-p "Stopped" plain))))
+    (test-header--teardown)))
+
+(ert-deftest test-music-config--header-text-boundary-paused-state ()
+  "Header shows 'Paused' when player is paused."
+  (unwind-protect
+      (progn
+        (test-header--setup-playlist-buffer '("/music/a.mp3"))
+        (setq emms-player-playing-p t)
+        (setq emms-player-paused-p t)
+        (let* ((header (with-current-buffer cj/music-playlist-buffer-name
+                         (cj/music--header-text)))
+               (plain (test-header--strip-properties header)))
+          (should (string-match-p "Paused" plain))))
+    (test-header--teardown)))
+
+(ert-deftest test-music-config--header-text-boundary-contains-mode-labels ()
+  "Header contains mode indicator labels for repeat, single, random, consume."
+  (unwind-protect
+      (progn
+        (test-header--setup-playlist-buffer '("/music/a.mp3"))
+        (let* ((header (with-current-buffer cj/music-playlist-buffer-name
+                         (cj/music--header-text)))
+               (plain (test-header--strip-properties header)))
+          (should (string-match-p "repeat" plain))
+          (should (string-match-p "single" plain))
+          (should (string-match-p "random" plain))
+          (should (string-match-p "consume" plain))))
+    (test-header--teardown)))
+
+;;; Error Cases
+
+(ert-deftest test-music-config--header-text-error-empty-playlist-shows-zero-count ()
+  "Header shows (0) for empty playlist."
+  (unwind-protect
+      (progn
+        (test-header--setup-playlist-buffer '())
+        (let* ((header (with-current-buffer cj/music-playlist-buffer-name
+                         (cj/music--header-text)))
+               (plain (test-header--strip-properties header)))
+          (should (string-match-p "(0)" plain))))
+    (test-header--teardown)))
+
+(provide 'test-music-config--header-text)
+;;; test-music-config--header-text.el ends here