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+;;; test-ai-vterm--pick-buffer-candidates.el --- Tests for the M-F9 candidate builder -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; The candidate builder is a pure function: given an MRU list of
+;; alive AI-vterm buffers and the currently-displayed buffer (or
+;; nil), it returns an alist of (DISPLAY-NAME . BUFFER) cells.
+;;
+;; Sort rule: non-shown buffers come first in their input order,
+;; then the shown buffer (if it's in the list) appears last with a
+;; \" [shown]\" suffix.  The intent is that the default `completing-
+;; read' selection lands on a non-shown candidate so RET means
+;; \"give me the other one\".
+
+;;; Code:
+
+(require 'ert)
+
+(add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+(require 'ai-vterm)
+
+(defun test-ai-vterm--pbc-cleanup ()
+  "Kill any leftover claude-prefixed buffers."
+  (dolist (b (buffer-list))
+    (when (string-prefix-p "claude [" (buffer-name b))
+      (kill-buffer b))))
+
+(ert-deftest test-ai-vterm--pick-buffer-candidates-empty-buffers ()
+  "Boundary: empty buffer list -> empty alist regardless of shown."
+  (test-ai-vterm--pbc-cleanup)
+  (should (null (cj/--ai-vterm-pick-buffer-candidates nil nil)))
+  (should (null (cj/--ai-vterm-pick-buffer-candidates nil 'sentinel))))
+
+(ert-deftest test-ai-vterm--pick-buffer-candidates-shown-nil ()
+  "Normal: shown is nil -> straight alist in input order, no marker."
+  (test-ai-vterm--pbc-cleanup)
+  (let ((b1 (get-buffer-create "claude [a]"))
+        (b2 (get-buffer-create "claude [b]")))
+    (unwind-protect
+        (let ((result (cj/--ai-vterm-pick-buffer-candidates (list b1 b2) nil)))
+          (should (equal result `(("claude [a]" . ,b1)
+                                   ("claude [b]" . ,b2)))))
+      (kill-buffer b1)
+      (kill-buffer b2))))
+
+(ert-deftest test-ai-vterm--pick-buffer-candidates-shown-promotes-non-shown ()
+  "Normal: shown buffer sorts last with [shown] suffix; others first."
+  (test-ai-vterm--pbc-cleanup)
+  (let ((b1 (get-buffer-create "claude [a]"))
+        (b2 (get-buffer-create "claude [b]"))
+        (b3 (get-buffer-create "claude [c]")))
+    (unwind-protect
+        (let ((result (cj/--ai-vterm-pick-buffer-candidates
+                       (list b1 b2 b3) b1)))
+          (should (equal result
+                         `(("claude [b]" . ,b2)
+                           ("claude [c]" . ,b3)
+                           ("claude [a] [shown]" . ,b1)))))
+      (kill-buffer b1)
+      (kill-buffer b2)
+      (kill-buffer b3))))
+
+(ert-deftest test-ai-vterm--pick-buffer-candidates-shown-only-buffer ()
+  "Boundary: shown is the only entry -> single cell with [shown] marker."
+  (test-ai-vterm--pbc-cleanup)
+  (let ((b1 (get-buffer-create "claude [a]")))
+    (unwind-protect
+        (let ((result (cj/--ai-vterm-pick-buffer-candidates (list b1) b1)))
+          (should (equal result `(("claude [a] [shown]" . ,b1)))))
+      (kill-buffer b1))))
+
+(ert-deftest test-ai-vterm--pick-buffer-candidates-shown-not-in-buffers ()
+  "Boundary: stale shown buffer not in list -> all cells are non-shown."
+  (test-ai-vterm--pbc-cleanup)
+  (let ((b1 (get-buffer-create "claude [a]"))
+        (b-stale (get-buffer-create "claude [stale]")))
+    (unwind-protect
+        (let ((result (cj/--ai-vterm-pick-buffer-candidates
+                       (list b1) b-stale)))
+          (should (equal result `(("claude [a]" . ,b1)))))
+      (kill-buffer b1)
+      (kill-buffer b-stale))))
+
+(provide 'test-ai-vterm--pick-buffer-candidates)
+;;; test-ai-vterm--pick-buffer-candidates.el ends here