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+;;; test-music-config--bar-string.el --- Tests for the block progress bar -*- coding: utf-8; lexical-binding: t; -*-
+;;
+;; Author: Craig Jennings <c@cjennings.net>
+;;
+;;; Commentary:
+;; Unit tests for `cj/music--bar-string': render a WIDTH-cell block bar from a
+;; filled-cell count (from `cj/music--bar-fill'), or an "on air" marker when the
+;; fill is `indeterminate' (a live stream with no duration).  Face-carrying
+;; text; the tests assert the rendered length and content, not the faces.
+;;
+;;; Code:
+
+(require 'ert)
+
+(defvar-keymap cj/custom-keymap :doc "Stub keymap for 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 'music-config)
+
+(ert-deftest test-music-config--bar-string-normal-half ()
+  "Normal: 10 of 20 cells filled renders a 20-cell bar."
+  (let ((s (substring-no-properties (cj/music--bar-string 10 20))))
+    (should (= (length s) 20))
+    (should (= (cl-count ?█ s) 10))
+    (should (= (cl-count ?░ s) 10))))
+
+(ert-deftest test-music-config--bar-string-boundary-empty ()
+  "Boundary: zero fill is all empty cells."
+  (let ((s (substring-no-properties (cj/music--bar-string 0 20))))
+    (should (= (cl-count ?█ s) 0))
+    (should (= (cl-count ?░ s) 20))))
+
+(ert-deftest test-music-config--bar-string-boundary-full ()
+  "Boundary: full fill is all filled cells."
+  (let ((s (substring-no-properties (cj/music--bar-string 20 20))))
+    (should (= (cl-count ?█ s) 20))
+    (should (= (cl-count ?░ s) 0))))
+
+(ert-deftest test-music-config--bar-string-indeterminate-on-air ()
+  "Error/indeterminate: a stream renders an on-air marker, not a bar."
+  (let ((s (substring-no-properties (cj/music--bar-string 'indeterminate 20))))
+    (should (string-match-p "on air" s))
+    (should (= (cl-count ?█ s) 0))))
+
+(provide 'test-music-config--bar-string)
+;;; test-music-config--bar-string.el ends here