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+;;; test-ledger-config.el --- Characterization tests for ledger-config -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; Captures the behavior ledger-config.el has today, before any guardrail work
+;; changes it.  See docs/design/2026-07-10-ledger-config-audit.org for the audit
+;; these tests pin.
+;;
+;; The clean-on-save helpers are defined in the `use-package' `:preface', which
+;; use-package emits unconditionally, so they exist under `make test' even though
+;; ledger-mode itself never loads there (no `package-initialize' in the test run).
+;;
+;; `ledger-mode-clean-buffer' is stubbed: it is the boundary this config delegates
+;; to, and it rewrites the whole buffer.  What these tests pin is whether our hook
+;; calls it, not what it does.
+
+;;; Code:
+
+(require 'ert)
+(require 'cl-lib)
+
+(add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+(require 'ledger-config)
+
+(ert-deftest test-ledger-config-clean-before-save-cleans-when-enabled ()
+  "Normal: with `cj/ledger-clean-on-save' set, the save hook cleans the buffer."
+  (let ((called 0)
+        (cj/ledger-clean-on-save t))
+    (cl-letf (((symbol-function 'ledger-mode-clean-buffer)
+               (lambda (&rest _) (setq called (1+ called)))))
+      (cj/ledger--clean-before-save))
+    (should (= 1 called))))
+
+(ert-deftest test-ledger-config-clean-before-save-skips-when-disabled ()
+  "Boundary: with `cj/ledger-clean-on-save' nil, the save hook does nothing."
+  (let ((called 0)
+        (cj/ledger-clean-on-save nil))
+    (cl-letf (((symbol-function 'ledger-mode-clean-buffer)
+               (lambda (&rest _) (setq called (1+ called)))))
+      (cj/ledger--clean-before-save))
+    (should (= 0 called))))
+
+(ert-deftest test-ledger-config-clean-before-save-demotes-errors ()
+  "Error: a failing clean does not signal, so the file still saves.
+This is the current contract.  It also means a clean that fails partway
+leaves the buffer in whatever state it reached, because nothing rolls back."
+  (let ((cj/ledger-clean-on-save t)
+        (inhibit-message t))
+    (cl-letf (((symbol-function 'ledger-mode-clean-buffer)
+               (lambda (&rest _) (error "boom"))))
+      (should (progn (cj/ledger--clean-before-save) t)))))
+
+(ert-deftest test-ledger-config-enable-clean-on-save-is-buffer-local ()
+  "Normal: the hook installs buffer-locally, not globally."
+  (let ((global-before (default-value 'before-save-hook)))
+    (with-temp-buffer
+      (cj/ledger--enable-clean-on-save)
+      (should (memq #'cj/ledger--clean-before-save before-save-hook))
+      (should-not (memq #'cj/ledger--clean-before-save
+                        (default-value 'before-save-hook))))
+    (should (equal global-before (default-value 'before-save-hook)))))
+
+(ert-deftest test-ledger-config-clean-on-save-defaults-on ()
+  "Normal: clean-on-save ships enabled.
+Pinned because the audit questions whether a whole-buffer sort belongs on
+every save of a financial file.  If that default flips, this test should
+fail and be updated deliberately."
+  (should (eq t (default-value 'cj/ledger-clean-on-save))))
+
+(provide 'test-ledger-config)
+;;; test-ledger-config.el ends here