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+;;; test-undead-buffers--warnings-undead.el --- *Warnings* survives the buffer sweep -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; Emacs 31.1's warnings.el defers daemon-startup warnings into a one-shot
+;; `after-make-frame-functions' closure that holds the *Warnings* buffer
+;; object and displays it on the first client frame.  Killing that buffer
+;; during startup leaves the closure holding a dead buffer, `display-buffer'
+;; then signals inside `make-frame', server.el reports the window system as
+;; unsupported, and emacsclient silently retries on $DISPLAY -- the first
+;; frame of the session lands on XWayland instead of Wayland.
+;;
+;; `cj/dashboard-only' on `emacs-startup-hook' runs
+;; `cj/kill-all-other-buffers-and-windows', which is exactly such a sweep.
+;; These tests pin *Warnings* to the undead list so the sweep buries it
+;; instead of killing it.  Error-path coverage of the predicate itself (a nil
+;; or non-string name) lives in test-undead-buffers--buffer-undead-p.el.
+
+;;; Code:
+
+(require 'ert)
+(add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+(require 'undead-buffers)
+
+;;; Normal Cases
+
+(ert-deftest test-undead-buffers-warnings-is-undead-by-default ()
+  "Normal: the module's default list makes *Warnings* bury-only."
+  (should (member "*Warnings*" cj/undead-buffer-list))
+  (should (cj/--buffer-undead-p "*Warnings*")))
+
+(ert-deftest test-undead-buffers-warnings-survives-kill-all-other-buffers ()
+  "Normal: the startup sweep buries *Warnings* rather than killing it.
+This is the sweep `cj/dashboard-only' runs from `emacs-startup-hook'."
+  (delete-other-windows)
+  (unwind-protect
+      (let* ((main (current-buffer))
+             (existing (get-buffer "*Warnings*"))
+             (warnings (or existing (get-buffer-create "*Warnings*")))
+             (victim (generate-new-buffer "*test-sweep-victim*")))
+        (unwind-protect
+            (progn
+              (cj/kill-all-other-buffers-and-windows)
+              (should (buffer-live-p main))
+              (should (buffer-live-p warnings))
+              (should-not (buffer-live-p victim)))
+          (when (buffer-live-p victim) (kill-buffer victim))
+          ;; Only remove what this test created.  `kill-buffer' the function
+          ;; is not the remapped command, so the undead list doesn't apply.
+          (when (and (not existing) (buffer-live-p warnings))
+            (kill-buffer warnings))))
+    (delete-other-windows)))
+
+;;; Boundary Cases
+
+(ert-deftest test-undead-buffers-warnings-match-is-exact ()
+  "Boundary: only the exact name is undead; a uniquified *Warnings*<2> is not.
+The list matches exact names, so a second warnings buffer made by
+`generate-new-buffer' is an ordinary buffer to the sweep."
+  (should-not (cj/--buffer-undead-p "*Warnings*<2>"))
+  (should-not (cj/--buffer-undead-p " *Warnings*")))
+
+(provide 'test-undead-buffers--warnings-undead)
+;;; test-undead-buffers--warnings-undead.el ends here