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+;;; test-undead-buffers--save-some-buffers-override-no-conflict.el --- Regression: save override vs undead -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; Regression guard for a launch crash.  custom-buffer-file.el installs a
+;; legible `save-some-buffers' override named `cj/save-some-buffers' (arity
+;; arg + pred).  undead-buffers.el used to define its own 1-arg
+;; `cj/save-some-buffers' that called `save-some-buffers' internally.  In prod
+;; load order (custom-buffer-file before undead-buffers) the 1-arg version won
+;; the symbol, so the override re-entered it with two args and signalled
+;; wrong-number-of-arguments — crashing the kill-all-other-buffers startup path.
+;;
+;; The requires below reproduce that prod order on purpose.
+
+;;; Code:
+
+(require 'ert)
+;; Prod order: override installed first, undead-buffers loaded second.
+(require 'custom-buffer-file)
+(require 'undead-buffers)
+
+(ert-deftest test-undead-buffers-save-override-accepts-predicate ()
+  "Normal: calling `save-some-buffers' with the undead predicate (the
+kill-all-other-buffers path) goes through the legible override without a
+wrong-number-of-arguments crash.  No modified file buffers exist in batch, so
+the override returns a count rather than prompting."
+  (should (numberp (save-some-buffers nil #'cj/undead-buffer-p))))
+
+(ert-deftest test-undead-buffers-save-some-buffers-not-arity-shadowed ()
+  "Boundary: `cj/save-some-buffers' must accept the PRED argument the override
+forwards (max arity >= 2), so undead-buffers can't reintroduce a 1-arg shadow."
+  (should (>= (cdr (func-arity #'cj/save-some-buffers)) 2)))
+
+(provide 'test-undead-buffers--save-some-buffers-override-no-conflict)
+;;; test-undead-buffers--save-some-buffers-override-no-conflict.el ends here