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+;;; test-music-config--get-m3u-files.el --- Tests for M3U file discovery -*- coding: utf-8; lexical-binding: t; -*-
+;;
+;; Author: Craig Jennings <c@cjennings.net>
+;;
+;;; Commentary:
+;; Unit tests for cj/music--get-m3u-files function.
+;; Tests the helper that discovers M3U files in the music directory.
+;;
+;; Test organization:
+;; - Normal Cases: Multiple M3U files, single file
+;; - Boundary Cases: Empty directory, non-M3U files, various filenames
+;; - Error Cases: Nonexistent directory
+;;
+;;; Code:
+
+(require 'ert)
+(require 'testutil-general)
+
+;; Stub missing dependencies before loading music-config
+(defvar-keymap cj/custom-keymap
+  :doc "Stub keymap for testing")
+
+;; Load production code
+(require 'music-config)
+
+;;; Setup & Teardown
+
+(defun test-music-config--get-m3u-files-setup ()
+  "Setup test environment."
+  (cj/create-test-base-dir))
+
+(defun test-music-config--get-m3u-files-teardown ()
+  "Clean up test environment."
+  (cj/delete-test-base-dir))
+
+;;; Normal Cases
+
+(ert-deftest test-music-config--get-m3u-files-normal-multiple-files-returns-list ()
+  "Discover multiple M3U files returns list of (basename . fullpath) conses."
+  (test-music-config--get-m3u-files-setup)
+  (unwind-protect
+      (let* ((test-dir (cj/create-test-subdirectory "playlists"))
+             (file1 (cj/create-temp-test-file-with-content "" "playlist1.m3u"))
+             (file2 (cj/create-temp-test-file-with-content "" "playlist2.m3u"))
+             (file3 (cj/create-temp-test-file-with-content "" "playlist3.m3u")))
+        ;; Move files to test-dir
+        (rename-file file1 (expand-file-name "playlist1.m3u" test-dir))
+        (rename-file file2 (expand-file-name "playlist2.m3u" test-dir))
+        (rename-file file3 (expand-file-name "playlist3.m3u" test-dir))
+
+        (let ((cj/music-m3u-root test-dir))
+          (let ((result (cj/music--get-m3u-files)))
+            (should (= (length result) 3))
+            ;; Check structure: list of (basename . fullpath) conses
+            ;; Sort for consistent comparison (directory-files order is filesystem-dependent)
+            (let ((basenames (sort (mapcar #'car result) #'string<))
+                  (fullpaths (sort (mapcar #'cdr result) #'string<)))
+              (should (equal basenames '("playlist1.m3u" "playlist2.m3u" "playlist3.m3u")))
+              (should (equal fullpaths
+                            (list (expand-file-name "playlist1.m3u" test-dir)
+                                  (expand-file-name "playlist2.m3u" test-dir)
+                                  (expand-file-name "playlist3.m3u" test-dir))))))))
+    (test-music-config--get-m3u-files-teardown)))
+
+(ert-deftest test-music-config--get-m3u-files-normal-single-file-returns-list ()
+  "Discover single M3U file returns single-item list."
+  (test-music-config--get-m3u-files-setup)
+  (unwind-protect
+      (let* ((test-dir (cj/create-test-subdirectory "playlists"))
+             (file1 (cj/create-temp-test-file-with-content "" "myplaylist.m3u")))
+        (rename-file file1 (expand-file-name "myplaylist.m3u" test-dir))
+
+        (let ((cj/music-m3u-root test-dir))
+          (let ((result (cj/music--get-m3u-files)))
+            (should (= (length result) 1))
+            (should (equal (caar result) "myplaylist.m3u"))
+            (should (equal (cdar result) (expand-file-name "myplaylist.m3u" test-dir))))))
+    (test-music-config--get-m3u-files-teardown)))
+
+;;; Boundary Cases
+
+(ert-deftest test-music-config--get-m3u-files-boundary-empty-directory-returns-empty ()
+  "Discover M3U files in empty directory returns empty list."
+  (test-music-config--get-m3u-files-setup)
+  (unwind-protect
+      (let* ((test-dir (cj/create-test-subdirectory "empty-playlists")))
+        (let ((cj/music-m3u-root test-dir))
+          (let ((result (cj/music--get-m3u-files)))
+            (should (null result)))))
+    (test-music-config--get-m3u-files-teardown)))
+
+(ert-deftest test-music-config--get-m3u-files-boundary-non-m3u-files-ignored ()
+  "Directory with non-M3U files returns empty list."
+  (test-music-config--get-m3u-files-setup)
+  (unwind-protect
+      (let* ((test-dir (cj/create-test-subdirectory "mixed-files"))
+             (txt-file (cj/create-temp-test-file-with-content "" "readme.txt"))
+             (mp3-file (cj/create-temp-test-file-with-content "" "song.mp3"))
+             (json-file (cj/create-temp-test-file-with-content "" "data.json")))
+        (rename-file txt-file (expand-file-name "readme.txt" test-dir))
+        (rename-file mp3-file (expand-file-name "song.mp3" test-dir))
+        (rename-file json-file (expand-file-name "data.json" test-dir))
+
+        (let ((cj/music-m3u-root test-dir))
+          (let ((result (cj/music--get-m3u-files)))
+            (should (null result)))))
+    (test-music-config--get-m3u-files-teardown)))
+
+(ert-deftest test-music-config--get-m3u-files-boundary-m3u-with-spaces-included ()
+  "M3U files with spaces in name are discovered."
+  (test-music-config--get-m3u-files-setup)
+  (unwind-protect
+      (let* ((test-dir (cj/create-test-subdirectory "playlists"))
+             (file1 (cj/create-temp-test-file-with-content "" "my-playlist.m3u")))
+        (rename-file file1 (expand-file-name "My Favorite Songs.m3u" test-dir))
+
+        (let ((cj/music-m3u-root test-dir))
+          (let ((result (cj/music--get-m3u-files)))
+            (should (= (length result) 1))
+            (should (equal (caar result) "My Favorite Songs.m3u")))))
+    (test-music-config--get-m3u-files-teardown)))
+
+(ert-deftest test-music-config--get-m3u-files-boundary-mixed-m3u-and-other-files ()
+  "Directory with both M3U and non-M3U files returns only M3U files."
+  (test-music-config--get-m3u-files-setup)
+  (unwind-protect
+      (let* ((test-dir (cj/create-test-subdirectory "mixed"))
+             (m3u-file (cj/create-temp-test-file-with-content "" "playlist.m3u"))
+             (txt-file (cj/create-temp-test-file-with-content "" "readme.txt"))
+             (mp3-file (cj/create-temp-test-file-with-content "" "song.mp3")))
+        (rename-file m3u-file (expand-file-name "playlist.m3u" test-dir))
+        (rename-file txt-file (expand-file-name "readme.txt" test-dir))
+        (rename-file mp3-file (expand-file-name "song.mp3" test-dir))
+
+        (let ((cj/music-m3u-root test-dir))
+          (let ((result (cj/music--get-m3u-files)))
+            (should (= (length result) 1))
+            (should (equal (caar result) "playlist.m3u")))))
+    (test-music-config--get-m3u-files-teardown)))
+
+;;; Error Cases
+
+(ert-deftest test-music-config--get-m3u-files-error-nonexistent-directory-signals-error ()
+  "Nonexistent directory signals error."
+  (let ((cj/music-m3u-root "/nonexistent/directory/path"))
+    (should-error (cj/music--get-m3u-files)
+                  :type 'file-error)))
+
+(provide 'test-music-config--get-m3u-files)
+;;; test-music-config--get-m3u-files.el ends here