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+;;; test-music-config--after-playlist-clear.el --- Tests for playlist clear advice -*- coding: utf-8; lexical-binding: t; -*-
+;;
+;; Author: Craig Jennings <c@cjennings.net>
+;;
+;;; Commentary:
+;; Unit tests for cj/music--after-playlist-clear function.
+;; Tests the advice function that resets cj/music-playlist-file
+;; when the EMMS playlist is cleared.
+;;
+;; Test organization:
+;; - Normal Cases: Clears file variable, noop when no buffer
+;; - Boundary Cases: Already nil stays nil, idempotent on multiple calls
+;; - Error Cases: Killed buffer doesn't crash
+;;
+;;; 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-after-clear--setup ()
+  "Create playlist buffer with a playlist file set."
+  (let ((buf (get-buffer-create cj/music-playlist-buffer-name)))
+    (with-current-buffer buf
+      (emms-playlist-mode)
+      (setq emms-playlist-buffer-p t))
+    (setq emms-playlist-buffer buf)
+    buf))
+
+(defun test-after-clear--teardown ()
+  "Clean up test playlist buffer."
+  (when-let ((buf (get-buffer cj/music-playlist-buffer-name)))
+    (with-current-buffer buf
+      (setq cj/music-playlist-file nil))
+    (kill-buffer buf)))
+
+;;; Normal Cases
+
+(ert-deftest test-music-config--after-playlist-clear-normal-clears-file-variable ()
+  "Calling after-playlist-clear sets cj/music-playlist-file to nil."
+  (unwind-protect
+      (progn
+        (test-after-clear--setup)
+        (with-current-buffer cj/music-playlist-buffer-name
+          (setq cj/music-playlist-file "/path/to/playlist.m3u"))
+        (cj/music--after-playlist-clear)
+        (with-current-buffer cj/music-playlist-buffer-name
+          (should-not cj/music-playlist-file)))
+    (test-after-clear--teardown)))
+
+(ert-deftest test-music-config--after-playlist-clear-normal-noop-when-no-buffer ()
+  "Does nothing when playlist buffer doesn't exist."
+  (unwind-protect
+      (progn
+        ;; Ensure no buffer exists
+        (when-let ((buf (get-buffer cj/music-playlist-buffer-name)))
+          (kill-buffer buf))
+        ;; Should not error
+        (cj/music--after-playlist-clear))
+    (test-after-clear--teardown)))
+
+;;; Boundary Cases
+
+(ert-deftest test-music-config--after-playlist-clear-boundary-already-nil-stays-nil ()
+  "Already-nil playlist file remains nil after clear."
+  (unwind-protect
+      (progn
+        (test-after-clear--setup)
+        (with-current-buffer cj/music-playlist-buffer-name
+          (setq cj/music-playlist-file nil))
+        (cj/music--after-playlist-clear)
+        (with-current-buffer cj/music-playlist-buffer-name
+          (should-not cj/music-playlist-file)))
+    (test-after-clear--teardown)))
+
+(ert-deftest test-music-config--after-playlist-clear-boundary-multiple-calls-idempotent ()
+  "Multiple calls produce same result as single call."
+  (unwind-protect
+      (progn
+        (test-after-clear--setup)
+        (with-current-buffer cj/music-playlist-buffer-name
+          (setq cj/music-playlist-file "/path/to/playlist.m3u"))
+        (cj/music--after-playlist-clear)
+        (cj/music--after-playlist-clear)
+        (cj/music--after-playlist-clear)
+        (with-current-buffer cj/music-playlist-buffer-name
+          (should-not cj/music-playlist-file)))
+    (test-after-clear--teardown)))
+
+;;; Error Cases
+
+(ert-deftest test-music-config--after-playlist-clear-error-killed-buffer-no-crash ()
+  "Killed buffer doesn't cause an error."
+  (let ((buf (test-after-clear--setup)))
+    (kill-buffer buf)
+    ;; Should not error when buffer is gone
+    (should-not (condition-case err
+                    (progn (cj/music--after-playlist-clear) nil)
+                  (error err)))))
+
+(provide 'test-music-config--after-playlist-clear)
+;;; test-music-config--after-playlist-clear.el ends here