test(system-defaults): cover custom-file, backups, and GC-hook registration

system-defaults.el had no coverage for its settings, only its functions (in test-system-defaults-functions.el) and the vc-follow-symlinks default. I added three settings smoke tests: custom-file is redirected to a temp trashbin rather than the repo, backups land under user-emacs-directory/backups, and the minibuffer GC hooks are actually wired onto the minibuffer hooks.

I pulled the sandbox loader the vc-follow-symlinks test had inline into tests/testutil-system-defaults.el so both files share one copy. The backups test clears cj/backup-directory before loading — it's a defvar, so once an earlier test loads the module it keeps that first sandbox path and won't recompute, which made the assertion fail until I forced the recompute.

3 files changed, 142 insertions, 49 deletions

diff --git a/tests/test-system-defaults-vc-follow-symlinks.el b/tests/test-system-defaults-vc-follow-symlinks.el
index 34406986..e8966d7b 100644
--- a/tests/test-system-defaults-vc-follow-symlinks.el
+++ b/tests/test-system-defaults-vc-follow-symlinks.el
@@ -7,60 +7,16 @@
 
 ;;; Code:
 
-(require 'cl-lib)
-(require 'autorevert)
-(require 'bookmark)
 (require 'ert)
-(require 'server)
-(require 'vc-hooks)
-
-(defvar org-dir nil
-  "Test binding for system-defaults bookmark path setup.")
-
-(defvar user-home-dir nil
-  "Test binding for system-defaults default directory setup.")
-
-(defvar use-package-always-ensure nil
-  "Test binding for use-package package installation policy.")
-
-(defconst test-system-defaults--repo-root
-  (file-name-directory
-   (directory-file-name
-    (file-name-directory (or load-file-name buffer-file-name))))
-  "Repository root for system-defaults tests.")
-
-(defmacro test-system-defaults--with-load-environment (&rest body)
-  "Run BODY with side effects from system-defaults.el stubbed."
-  `(let ((user-emacs-directory (file-name-as-directory
-                                (make-temp-file "system-defaults-emacs-" t)))
-         (user-home-dir (file-name-as-directory
-                         (make-temp-file "system-defaults-home-" t)))
-         (org-dir (file-name-as-directory
-                   (make-temp-file "system-defaults-org-" t)))
-         (use-package-always-ensure nil))
-     (cl-letf (((symbol-function 'server-running-p) (lambda (&rest _) t))
-               ((symbol-function 'server-start) #'ignore)
-               ((symbol-function 'set-locale-environment) #'ignore)
-               ((symbol-function 'prefer-coding-system) #'ignore)
-               ((symbol-function 'set-default-coding-systems) #'ignore)
-               ((symbol-function 'set-terminal-coding-system) #'ignore)
-               ((symbol-function 'set-keyboard-coding-system) #'ignore)
-               ((symbol-function 'set-selection-coding-system) #'ignore)
-               ((symbol-function 'set-charset-priority) #'ignore)
-               ((symbol-function 'global-auto-revert-mode) #'ignore)
-               ((symbol-function 'recentf-mode) #'ignore))
-       (unless (fboundp 'use-package)
-         (defmacro use-package (&rest _args) nil))
-       ,@body)))
+(add-to-list 'load-path (expand-file-name "tests" user-emacs-directory))
+(require 'testutil-system-defaults)
 
 (ert-deftest test-system-defaults-vc-follow-symlinks-normal-sets-t ()
   "Normal: system-defaults follows version-controlled symlinks without asking."
   (test-system-defaults--with-load-environment
-   (let ((vc-follow-symlinks nil))
-     (load (expand-file-name "modules/system-defaults.el"
-                             test-system-defaults--repo-root)
-           nil t)
-     (should (eq vc-follow-symlinks t)))))
+    (let ((vc-follow-symlinks nil))
+      (test-system-defaults--load)
+      (should (eq vc-follow-symlinks t)))))
 
 (provide 'test-system-defaults-vc-follow-symlinks)
 ;;; test-system-defaults-vc-follow-symlinks.el ends here
diff --git a/tests/test-system-defaults.el b/tests/test-system-defaults.el
new file mode 100644
index 00000000..bc3694db
--- /dev/null
+++ b/tests/test-system-defaults.el
@@ -0,0 +1,68 @@
+;;; test-system-defaults.el --- Smoke tests for system-defaults settings -*- lexical-binding: t; -*-
+
+;;; Commentary:
+
+;; system-defaults.el holds high-impact defaults with no behavior of its own
+;; to unit-test, so these are characterization smoke tests on the *settings*
+;; most likely to cause damage if they regressed silently: where Customize
+;; writes land, where backups go, and whether the minibuffer GC hooks are
+;; installed.  Load happens in the shared sandbox (testutil-system-defaults.el).
+;;
+;; The module's functions (cj/disabled, the GC hook bodies, unpropertize-kill-ring,
+;; cj/log-comp-warning) are covered by test-system-defaults-functions.el, and the
+;; vc-follow-symlinks default by test-system-defaults-vc-follow-symlinks.el.
+
+;;; Code:
+
+(require 'ert)
+(add-to-list 'load-path (expand-file-name "tests" user-emacs-directory))
+(require 'testutil-system-defaults)
+
+;;; custom-file redirection
+
+(ert-deftest test-system-defaults-custom-file-redirected-to-tempfile ()
+  "Normal: custom-file points at a throwaway temp file, never the repo.
+This is what stops accidental Customize writes from landing in tracked init."
+  (test-system-defaults--with-load-environment
+    (let ((custom-file nil))
+      (test-system-defaults--load)
+      (should (stringp custom-file))
+      (should (string-prefix-p (file-name-as-directory
+                                (expand-file-name temporary-file-directory))
+                               (expand-file-name custom-file)))
+      (should (string-match-p "emacs-customizations-trashbin-"
+                              (file-name-nondirectory custom-file)))
+      (should-not (string-prefix-p (expand-file-name user-emacs-directory)
+                                   (expand-file-name custom-file))))))
+
+;;; backup directory
+
+(ert-deftest test-system-defaults-backups-redirected-under-user-emacs-dir ()
+  "Normal: backups are redirected into user-emacs-directory/backups.
+cj/backup-directory is a defvar that only recomputes when unbound, so the
+test clears it first to capture the path derived from the sandbox."
+  (test-system-defaults--with-load-environment
+    (makunbound 'cj/backup-directory)
+    (let ((backup-directory-alist nil))
+      (test-system-defaults--load)
+      (let ((dir (cdr (assoc "." backup-directory-alist))))
+        (should dir)
+        (should (string-prefix-p (expand-file-name user-emacs-directory)
+                                 (expand-file-name dir)))
+        (should (string-suffix-p "backups" (directory-file-name dir)))))))
+
+;;; minibuffer GC hooks
+
+(ert-deftest test-system-defaults-minibuffer-gc-hooks-registered ()
+  "Normal: the minibuffer GC raise/restore hooks are installed.
+Their bodies are tested in test-system-defaults-functions.el; this asserts
+they are actually wired onto the minibuffer hooks."
+  (test-system-defaults--with-load-environment
+    (let ((minibuffer-setup-hook nil)
+          (minibuffer-exit-hook nil))
+      (test-system-defaults--load)
+      (should (memq 'cj/minibuffer-setup-hook minibuffer-setup-hook))
+      (should (memq 'cj/minibuffer-exit-hook minibuffer-exit-hook)))))
+
+(provide 'test-system-defaults)
+;;; test-system-defaults.el ends here
diff --git a/tests/testutil-system-defaults.el b/tests/testutil-system-defaults.el
new file mode 100644
index 00000000..d1e669dc
--- /dev/null
+++ b/tests/testutil-system-defaults.el
@@ -0,0 +1,69 @@
+;;; testutil-system-defaults.el --- Shared load harness for system-defaults tests -*- lexical-binding: t; -*-
+
+;;; Commentary:
+
+;; system-defaults.el has startup side effects (server start, coding-system
+;; setup, recentf, file creation under `user-emacs-directory').  Tests that
+;; assert one of its settings load the module fresh in a sandbox with those
+;; external interactions stubbed, then inspect the variable they own.  This
+;; file holds that harness so each system-defaults test file shares one copy.
+
+;;; Code:
+
+(require 'cl-lib)
+(require 'autorevert)
+(require 'bookmark)
+(require 'server)
+(require 'vc-hooks)
+
+(defvar org-dir nil
+  "Test binding for system-defaults bookmark path setup.")
+
+(defvar user-home-dir nil
+  "Test binding for system-defaults default directory setup.")
+
+(defvar use-package-always-ensure nil
+  "Test binding for use-package package installation policy.")
+
+(defconst test-system-defaults--repo-root
+  (file-name-directory
+   (directory-file-name
+    (file-name-directory (or load-file-name buffer-file-name))))
+  "Repository root, derived from this file's location under tests/.")
+
+(defmacro test-system-defaults--with-load-environment (&rest body)
+  "Run BODY with the side effects of loading system-defaults.el stubbed.
+`user-emacs-directory', `user-home-dir', and `org-dir' are redirected to
+throwaway temp directories so file creation lands in the sandbox."
+  (declare (indent 0))
+  `(let ((user-emacs-directory (file-name-as-directory
+                                (make-temp-file "system-defaults-emacs-" t)))
+         (user-home-dir (file-name-as-directory
+                         (make-temp-file "system-defaults-home-" t)))
+         (org-dir (file-name-as-directory
+                   (make-temp-file "system-defaults-org-" t)))
+         (use-package-always-ensure nil))
+     (cl-letf (((symbol-function 'server-running-p) (lambda (&rest _) t))
+               ((symbol-function 'server-start) #'ignore)
+               ((symbol-function 'set-locale-environment) #'ignore)
+               ((symbol-function 'prefer-coding-system) #'ignore)
+               ((symbol-function 'set-default-coding-systems) #'ignore)
+               ((symbol-function 'set-terminal-coding-system) #'ignore)
+               ((symbol-function 'set-keyboard-coding-system) #'ignore)
+               ((symbol-function 'set-selection-coding-system) #'ignore)
+               ((symbol-function 'set-charset-priority) #'ignore)
+               ((symbol-function 'global-auto-revert-mode) #'ignore)
+               ((symbol-function 'recentf-mode) #'ignore))
+       (unless (fboundp 'use-package)
+         (defmacro use-package (&rest _args) nil))
+       ,@body)))
+
+(defun test-system-defaults--load ()
+  "Load system-defaults.el fresh from the repo for a smoke assertion.
+Call inside `test-system-defaults--with-load-environment'."
+  (load (expand-file-name "modules/system-defaults.el"
+                          test-system-defaults--repo-root)
+        nil t))
+
+(provide 'testutil-system-defaults)
+;;; testutil-system-defaults.el ends here