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diff --git a/scripts/theme-studio/test-face-docs-dump.el b/scripts/theme-studio/test-face-docs-dump.el
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+++ b/scripts/theme-studio/test-face-docs-dump.el
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+;;; test-face-docs-dump.el --- ERT tests for face-docs-dump.el -*- lexical-binding: t -*-
+
+;;; Commentary:
+;; Tests the pure docstring-extraction helper (`face-docs--first-line') and the
+;; syntax-category resolution (`face-docs--syntax-map') in face-docs-dump.el, the
+;; asset generator behind theme-studio's element hovers.  The faces map is a
+;; thin `face-list' walk over `face-docs--first-line', so testing the helper and
+;; the syntax resolution covers the logic that can actually be wrong.
+;;
+;; Self-locating: loads face-docs-dump.el and build-theme.el (for the
+;; category->face map) from this file's own directory, so the runner only needs
+;; to `-l' this file.
+
+;;; Code:
+
+(require 'ert)
+
+(let ((dir (file-name-directory
+            (or load-file-name buffer-file-name default-directory))))
+  (load (expand-file-name "face-docs-dump.el" dir) nil t)
+  (load (expand-file-name "build-theme.el" dir) nil t))
+
+;;; --- face-docs--first-line ---
+
+(ert-deftest test-face-docs-first-line-normal-multiline ()
+  "Normal: returns the first line of a multi-line docstring."
+  (should (equal (face-docs--first-line "First line.\nSecond line.")
+                 "First line.")))
+
+(ert-deftest test-face-docs-first-line-single-line ()
+  "Normal: a single-line docstring returns unchanged."
+  (should (equal (face-docs--first-line "Just one.") "Just one.")))
+
+(ert-deftest test-face-docs-first-line-skips-leading-blank-lines ()
+  "Boundary: leading blank lines are skipped to the first real line, trimmed."
+  (should (equal (face-docs--first-line "\n\n  Real line.\nrest")
+                 "Real line.")))
+
+(ert-deftest test-face-docs-first-line-collapses-internal-whitespace ()
+  "Boundary: runs of spaces and tabs inside the line collapse to one space."
+  (should (equal (face-docs--first-line "A  B\tC") "A B C")))
+
+(ert-deftest test-face-docs-first-line-empty-is-nil ()
+  "Boundary: an empty string yields nil."
+  (should (null (face-docs--first-line ""))))
+
+(ert-deftest test-face-docs-first-line-whitespace-only-is-nil ()
+  "Boundary: a blank/whitespace-only docstring yields nil."
+  (should (null (face-docs--first-line "   \n\t ")))
+  (should (null (face-docs--first-line "   "))))
+
+(ert-deftest test-face-docs-first-line-non-string-is-nil ()
+  "Error: nil, a number, or the :null sentinel yields nil."
+  (should (null (face-docs--first-line nil)))
+  (should (null (face-docs--first-line 42)))
+  (should (null (face-docs--first-line :null))))
+
+;;; --- face-docs--syntax-map ---
+
+(ert-deftest test-face-docs-syntax-map-resolves-category-to-face-doc ()
+  "Normal: kw resolves to font-lock-keyword-face's first docstring line."
+  (let ((m (face-docs--syntax-map)))
+    (should (stringp (gethash "kw" m)))
+    (should (string-match-p "keyword" (downcase (gethash "kw" m))))))
+
+(ert-deftest test-face-docs-syntax-map-bg-and-p-are-default ()
+  "Boundary: bg and p resolve to the default face's docstring."
+  (let ((m (face-docs--syntax-map))
+        (def (face-docs--first-line (face-documentation 'default))))
+    (should (equal (gethash "bg" m) def))
+    (should (equal (gethash "p" m) def))))
+
+(ert-deftest test-face-docs-syntax-map-omits-faceless-category ()
+  "Boundary: dec (Emacs has no dedicated decorator face) is absent."
+  (should (null (gethash "dec" (face-docs--syntax-map)))))
+
+(provide 'test-face-docs-dump)
+;;; test-face-docs-dump.el ends here