refactor(tests): extract shared buffer-cleanup and fake-vterm helpers

Eight test files across the ai-vterm and vterm-toggle suites each shipped a small variant of the same cleanup loop: walk `buffer-list`, kill any buffer whose name starts with a given prefix. Each file also re-implemented the `(string-prefix-p ...)` check inline. One file additionally had its own fake-vterm-mode-buffer constructor for tests that needed `cj/--vterm-toggle-buffer-p` to fire.

I pulled the shared logic into `tests/testutil-vterm-buffers.el`:

- `cj/test--kill-buffers-matching-prefix` is the primitive.
- `cj/test--kill-claude-buffers` and `cj/test--kill-test-vterm-buffers` are thin wrappers for the two prefixes that actually appear.
- `cj/test--make-fake-vterm-buffer` constructs a buffer with `major-mode` set to `vterm-mode` without launching a real vterm process.

Each affected test file now `(require 'testutil-vterm-buffers)` and calls the shared helpers directly. `test-vterm-toggle--buffer-filter.el` keeps a 3-line wrapper that calls both kill helpers in sequence (the only place that needs both prefixes). Net diff: -116 / +72 across 8 test files, plus ~30 lines in the new testutil. Roughly -45 lines after the abstraction is paid for.

No behavior change. 80 ai-vterm tests, 15 vterm-toggle tests, 15 cj-window-geometry tests all pass. Full make test green.

9 files changed, 101 insertions, 101 deletions

diff --git a/tests/test-ai-vterm--claude-buffers.el b/tests/test-ai-vterm--claude-buffers.el
index 56668ca1..f975b64e 100644
--- a/tests/test-ai-vterm--claude-buffers.el
+++ b/tests/test-ai-vterm--claude-buffers.el
@@ -12,24 +12,20 @@
 (require 'ert)
 
 (add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+(add-to-list 'load-path (expand-file-name "tests" user-emacs-directory))
 (require 'ai-vterm)
-
-(defun test-ai-vterm--claude-buffers-cleanup ()
-  "Kill any leftover claude-prefixed buffers before/after a test."
-  (dolist (b (buffer-list))
-    (when (string-prefix-p "claude [" (buffer-name b))
-      (kill-buffer b))))
+(require 'testutil-vterm-buffers)
 
 (ert-deftest test-ai-vterm--claude-buffers-empty-when-none-exist ()
   "Boundary: no claude-prefixed buffers anywhere -> empty list."
-  (test-ai-vterm--claude-buffers-cleanup)
+  (cj/test--kill-claude-buffers)
   (unwind-protect
       (should (null (cj/--ai-vterm-claude-buffers)))
-    (test-ai-vterm--claude-buffers-cleanup)))
+    (cj/test--kill-claude-buffers)))
 
 (ert-deftest test-ai-vterm--claude-buffers-returns-only-claude-buffers ()
   "Normal: filters to only claude-prefixed buffers, leaves others alone."
-  (test-ai-vterm--claude-buffers-cleanup)
+  (cj/test--kill-claude-buffers)
   (let ((c1 (get-buffer-create "claude [a]"))
         (c2 (get-buffer-create "claude [b]"))
         (other (get-buffer-create "regular-buffer")))
@@ -45,7 +41,7 @@
 
 (ert-deftest test-ai-vterm--claude-buffers-anchors-prefix-not-substring ()
   "Boundary: 'foo claude [bar]' is not a claude buffer -- prefix anchored."
-  (test-ai-vterm--claude-buffers-cleanup)
+  (cj/test--kill-claude-buffers)
   (let ((not-claude (get-buffer-create "foo claude [bar]")))
     (unwind-protect
         (should-not (memq not-claude (cj/--ai-vterm-claude-buffers)))
@@ -53,7 +49,7 @@
 
 (ert-deftest test-ai-vterm--claude-buffers-bare-claude-not-included ()
   "Boundary: 'claude' alone (no bracket) doesn't match the 'claude [' prefix."
-  (test-ai-vterm--claude-buffers-cleanup)
+  (cj/test--kill-claude-buffers)
   (let ((bare (get-buffer-create "claude")))
     (unwind-protect
         (should-not (memq bare (cj/--ai-vterm-claude-buffers)))
diff --git a/tests/test-ai-vterm--dispatch.el b/tests/test-ai-vterm--dispatch.el
index 030b200d..8871af9a 100644
--- a/tests/test-ai-vterm--dispatch.el
+++ b/tests/test-ai-vterm--dispatch.el
@@ -14,13 +14,9 @@
 (require 'cl-lib)
 
 (add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+(add-to-list 'load-path (expand-file-name "tests" user-emacs-directory))
 (require 'ai-vterm)
-
-(defun test-ai-vterm--dispatch-cleanup ()
-  "Kill any leftover claude-prefixed buffers."
-  (dolist (b (buffer-list))
-    (when (string-prefix-p "claude [" (buffer-name b))
-      (kill-buffer b))))
+(require 'testutil-vterm-buffers)
 
 (ert-deftest test-ai-vterm--dispatch-window-displayed-returns-toggle-off ()
   "Normal: displayed claude window -> (toggle-off . WIN)."
@@ -32,7 +28,7 @@
 
 (ert-deftest test-ai-vterm--dispatch-no-window-single-buffer-returns-redisplay-recent ()
   "Normal: no displayed claude, one alive buffer -> redisplay-recent + buffer."
-  (test-ai-vterm--dispatch-cleanup)
+  (cj/test--kill-claude-buffers)
   (let ((b1 (get-buffer-create "claude [single]")))
     (unwind-protect
         (cl-letf (((symbol-function 'cj/--ai-vterm-displayed-claude-window)
@@ -48,7 +44,7 @@
 F9 redisplays the most-recently-selected claude (head of buffer-list
 order) rather than opening the project picker, so the user toggles
 THE claude they were last using.  Other claudes are reachable via M-F9."
-  (test-ai-vterm--dispatch-cleanup)
+  (cj/test--kill-claude-buffers)
   (let ((b1 (get-buffer-create "claude [a]"))
         (b2 (get-buffer-create "claude [b]")))
     (unwind-protect
@@ -63,7 +59,7 @@ THE claude they were last using.  Other claudes are reachable via M-F9."
 
 (ert-deftest test-ai-vterm--dispatch-no-window-zero-buffers-returns-pick-project ()
   "Boundary: no displayed claude, zero alive buffers -> pick-project."
-  (test-ai-vterm--dispatch-cleanup)
+  (cj/test--kill-claude-buffers)
   (cl-letf (((symbol-function 'cj/--ai-vterm-displayed-claude-window)
              (lambda (&optional _frame) nil))
             ((symbol-function 'cj/--ai-vterm-claude-buffers)
diff --git a/tests/test-ai-vterm--display-saved.el b/tests/test-ai-vterm--display-saved.el
index aa0dc5ee..2b2bad09 100644
--- a/tests/test-ai-vterm--display-saved.el
+++ b/tests/test-ai-vterm--display-saved.el
@@ -16,7 +16,9 @@
 (require 'cl-lib)
 
 (add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+(add-to-list 'load-path (expand-file-name "tests" user-emacs-directory))
 (require 'ai-vterm)
+(require 'testutil-vterm-buffers)
 
 (ert-deftest test-ai-vterm--display-saved-uses-defaults-when-state-nil ()
   "Normal: nil state -> direction=rightmost, size=cj/ai-vterm-window-width.
@@ -94,12 +96,6 @@ which window is selected."
       (cj/--ai-vterm-display-saved 'sentinel-buffer nil))
     (should (eq received-buf 'sentinel-buffer))))
 
-(defun test-ai-vterm--display-saved-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--display-saved-3window-roundtrip-preserves-body-width ()
   "Regression: capture+delete+display in a 3-window layout preserves body-width.
 
@@ -109,7 +105,7 @@ the new claude lands at a different position than the captured one
 of the right divider.  `window-body-width' is divider-independent
 and is what the user actually sees, so the assertion locks down
 the body match."
-  (test-ai-vterm--display-saved-cleanup)
+  (cj/test--kill-claude-buffers)
   (let ((claude-name "claude [3win-roundtrip]")
         (left-name "*test-3win-left*")
         (right-name "*test-3win-right*"))
@@ -144,11 +140,11 @@ the body match."
                   (should (eq captured-direction 'right)))))))
       (when (get-buffer left-name) (kill-buffer left-name))
       (when (get-buffer right-name) (kill-buffer right-name))
-      (test-ai-vterm--display-saved-cleanup))))
+      (cj/test--kill-claude-buffers))))
 
 (ert-deftest test-ai-vterm--display-saved-3window-claude-rightmost-roundtrip ()
   "Round-trip when claude is the rightmost window (no right divider)."
-  (test-ai-vterm--display-saved-cleanup)
+  (cj/test--kill-claude-buffers)
   (let ((claude-name "claude [rightmost]")
         (left-name "*test-rm-left*")
         (mid-name "*test-rm-mid*"))
@@ -173,11 +169,11 @@ the body match."
                   (should (= (window-body-width new-win) captured-size)))))))
       (when (get-buffer left-name) (kill-buffer left-name))
       (when (get-buffer mid-name) (kill-buffer mid-name))
-      (test-ai-vterm--display-saved-cleanup))))
+      (cj/test--kill-claude-buffers))))
 
 (ert-deftest test-ai-vterm--display-saved-3window-after-mouse-resize ()
   "Round-trip after a deliberate mid-window resize (mimics mouse-drag)."
-  (test-ai-vterm--display-saved-cleanup)
+  (cj/test--kill-claude-buffers)
   (let ((claude-name "claude [mouse-resize]")
         (left-name "*test-mr-left*")
         (right-name "*test-mr-right*"))
@@ -206,11 +202,11 @@ the body match."
                   (should (= (window-body-width new-win) captured-size)))))))
       (when (get-buffer left-name) (kill-buffer left-name))
       (when (get-buffer right-name) (kill-buffer right-name))
-      (test-ai-vterm--display-saved-cleanup))))
+      (cj/test--kill-claude-buffers))))
 
 (ert-deftest test-ai-vterm--display-saved-roundtrip-via-cj/ai-vterm-toggle ()
   "End-to-end: toggle-off via dispatch then redisplay -- preserves size."
-  (test-ai-vterm--display-saved-cleanup)
+  (cj/test--kill-claude-buffers)
   (let ((claude-name "claude [toggle-roundtrip]")
         (left-name "*test-tr-left*")
         (right-name "*test-tr-right*"))
@@ -240,11 +236,11 @@ the body match."
                     (should (= new-size before-size))))))))
       (when (get-buffer left-name) (kill-buffer left-name))
       (when (get-buffer right-name) (kill-buffer right-name))
-      (test-ai-vterm--display-saved-cleanup))))
+      (cj/test--kill-claude-buffers))))
 
 (ert-deftest test-ai-vterm--display-saved-two-toggle-cycles-stable ()
   "Two consecutive toggle-off+toggle-on cycles -- no compounding error."
-  (test-ai-vterm--display-saved-cleanup)
+  (cj/test--kill-claude-buffers)
   (let ((claude-name "claude [two-cycle]")
         (left-name "*test-2c-left*")
         (right-name "*test-2c-right*"))
@@ -277,13 +273,13 @@ the body match."
                     (should (= cycle2-size initial-size))))))))
       (when (get-buffer left-name) (kill-buffer left-name))
       (when (get-buffer right-name) (kill-buffer right-name))
-      (test-ai-vterm--display-saved-cleanup))))
+      (cj/test--kill-claude-buffers))))
 
 (ert-deftest test-ai-vterm--display-saved-craig-c-x-3-roundtrip ()
   "Reproduces Craig's repro from 2026-05-09:
 launch -> F9 -> dashboard splits via C-x 3 -> toggle off -> toggle on.
 Expected: new claude lands at the same total-width it had before."
-  (test-ai-vterm--display-saved-cleanup)
+  (cj/test--kill-claude-buffers)
   (let ((claude-name "claude [c-x-3-repro]")
         (dash-name "*test-cx3-dashboard*"))
     (unwind-protect
@@ -314,7 +310,7 @@ Expected: new claude lands at the same total-width it had before."
                   (should (windowp claude-win-3))
                   (should (= size-after size-before)))))))
       (when (get-buffer dash-name) (kill-buffer dash-name))
-      (test-ai-vterm--display-saved-cleanup))))
+      (cj/test--kill-claude-buffers))))
 
 (ert-deftest test-ai-vterm--toggle-after-buffer-move-no-extra-window ()
   "Regression: toggle-off must remove claude's window even when buffer-move
@@ -331,7 +327,7 @@ landing the user at N+1 windows instead of N.
 
 Assertion: after toggle-off+toggle-on, the window count is back to
 its pre-cycle value, regardless of `quit-restore' state."
-  (test-ai-vterm--display-saved-cleanup)
+  (cj/test--kill-claude-buffers)
   (let ((claude-name "claude [buffer-move-toggle]")
         (left-name "*test-bm-left*")
         (right-name "*test-bm-right*"))
@@ -364,7 +360,7 @@ its pre-cycle value, regardless of `quit-restore' state."
                   (should (= (length claude-windows) 1)))))))
       (when (get-buffer left-name) (kill-buffer left-name))
       (when (get-buffer right-name) (kill-buffer right-name))
-      (test-ai-vterm--display-saved-cleanup))))
+      (cj/test--kill-claude-buffers))))
 
 (provide 'test-ai-vterm--display-saved)
 ;;; test-ai-vterm--display-saved.el ends here
diff --git a/tests/test-ai-vterm--displayed-claude-window.el b/tests/test-ai-vterm--displayed-claude-window.el
index 283a1b3c..9f84f87b 100644
--- a/tests/test-ai-vterm--displayed-claude-window.el
+++ b/tests/test-ai-vterm--displayed-claude-window.el
@@ -10,24 +10,20 @@
 (require 'ert)
 
 (add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+(add-to-list 'load-path (expand-file-name "tests" user-emacs-directory))
 (require 'ai-vterm)
-
-(defun test-ai-vterm--displayed-cleanup ()
-  "Kill any leftover claude-prefixed buffers."
-  (dolist (b (buffer-list))
-    (when (string-prefix-p "claude [" (buffer-name b))
-      (kill-buffer b))))
+(require 'testutil-vterm-buffers)
 
 (ert-deftest test-ai-vterm--displayed-claude-window-no-buffers-returns-nil ()
   "Boundary: no claude buffers anywhere -> nil."
-  (test-ai-vterm--displayed-cleanup)
+  (cj/test--kill-claude-buffers)
   (save-window-excursion
     (delete-other-windows)
     (should-not (cj/--ai-vterm-displayed-claude-window))))
 
 (ert-deftest test-ai-vterm--displayed-claude-window-not-displayed-returns-nil ()
   "Boundary: claude buffer exists but not in any window -> nil."
-  (test-ai-vterm--displayed-cleanup)
+  (cj/test--kill-claude-buffers)
   (let ((b1 (get-buffer-create "claude [hidden]")))
     (unwind-protect
         (save-window-excursion
@@ -37,7 +33,7 @@
 
 (ert-deftest test-ai-vterm--displayed-claude-window-returns-window-when-displayed ()
   "Normal: claude buffer in a window -> returns that window."
-  (test-ai-vterm--displayed-cleanup)
+  (cj/test--kill-claude-buffers)
   (let ((b1 (get-buffer-create "claude [shown]")))
     (unwind-protect
         (save-window-excursion
@@ -51,7 +47,7 @@
 
 (ert-deftest test-ai-vterm--displayed-claude-window-ignores-non-claude-windows ()
   "Boundary: only a non-claude buffer is displayed -> nil."
-  (test-ai-vterm--displayed-cleanup)
+  (cj/test--kill-claude-buffers)
   (let ((other (get-buffer-create "regular-displayed-buffer")))
     (unwind-protect
         (save-window-excursion
diff --git a/tests/test-ai-vterm--pick-buffer-candidates.el b/tests/test-ai-vterm--pick-buffer-candidates.el
index 99ef7325..ddfd7529 100644
--- a/tests/test-ai-vterm--pick-buffer-candidates.el
+++ b/tests/test-ai-vterm--pick-buffer-candidates.el
@@ -16,23 +16,19 @@
 (require 'ert)
 
 (add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+(add-to-list 'load-path (expand-file-name "tests" 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))))
+(require 'testutil-vterm-buffers)
 
 (ert-deftest test-ai-vterm--pick-buffer-candidates-empty-buffers ()
   "Boundary: empty buffer list -> empty alist regardless of shown."
-  (test-ai-vterm--pbc-cleanup)
+  (cj/test--kill-claude-buffers)
   (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)
+  (cj/test--kill-claude-buffers)
   (let ((b1 (get-buffer-create "claude [a]"))
         (b2 (get-buffer-create "claude [b]")))
     (unwind-protect
@@ -44,7 +40,7 @@
 
 (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)
+  (cj/test--kill-claude-buffers)
   (let ((b1 (get-buffer-create "claude [a]"))
         (b2 (get-buffer-create "claude [b]"))
         (b3 (get-buffer-create "claude [c]")))
@@ -61,7 +57,7 @@
 
 (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)
+  (cj/test--kill-claude-buffers)
   (let ((b1 (get-buffer-create "claude [a]")))
     (unwind-protect
         (let ((result (cj/--ai-vterm-pick-buffer-candidates (list b1) b1)))
@@ -70,7 +66,7 @@
 
 (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)
+  (cj/test--kill-claude-buffers)
   (let ((b1 (get-buffer-create "claude [a]"))
         (b-stale (get-buffer-create "claude [stale]")))
     (unwind-protect
diff --git a/tests/test-ai-vterm--reuse-existing-claude.el b/tests/test-ai-vterm--reuse-existing-claude.el
index 4668188d..195e50a2 100644
--- a/tests/test-ai-vterm--reuse-existing-claude.el
+++ b/tests/test-ai-vterm--reuse-existing-claude.el
@@ -15,17 +15,13 @@
 (require 'ert)
 
 (add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+(add-to-list 'load-path (expand-file-name "tests" user-emacs-directory))
 (require 'ai-vterm)
-
-(defun test-ai-vterm--reuse-cleanup ()
-  "Kill any leftover claude-prefixed buffers."
-  (dolist (b (buffer-list))
-    (when (string-prefix-p "claude [" (buffer-name b))
-      (kill-buffer b))))
+(require 'testutil-vterm-buffers)
 
 (ert-deftest test-ai-vterm--reuse-existing-claude-swaps-buffer-when-window-exists ()
   "Normal: a claude window exists -> swap its buffer, return the window."
-  (test-ai-vterm--reuse-cleanup)
+  (cj/test--kill-claude-buffers)
   (save-window-excursion
     (delete-other-windows)
     (let ((existing (get-buffer-create "claude [existing]"))
@@ -42,7 +38,7 @@
 
 (ert-deftest test-ai-vterm--reuse-existing-claude-returns-nil-when-no-claude-window ()
   "Boundary: no claude window in frame -> nil (chain continues to next action)."
-  (test-ai-vterm--reuse-cleanup)
+  (cj/test--kill-claude-buffers)
   (save-window-excursion
     (delete-other-windows)
     (let ((new-buf (get-buffer-create "claude [no-existing]")))
@@ -52,7 +48,7 @@
 
 (ert-deftest test-ai-vterm--reuse-existing-claude-leaves-non-claude-windows-alone ()
   "Boundary: only non-claude windows in frame -> nil; other windows untouched."
-  (test-ai-vterm--reuse-cleanup)
+  (cj/test--kill-claude-buffers)
   (save-window-excursion
     (delete-other-windows)
     (let ((code-buf (get-buffer-create "*test-code-buffer*"))
@@ -76,7 +72,7 @@
 This is the C-F9-from-claude regression: with claude at the bottom
 and code on top, switching projects must replace the bottom window's
 buffer, not the top window's."
-  (test-ai-vterm--reuse-cleanup)
+  (cj/test--kill-claude-buffers)
   (save-window-excursion
     (delete-other-windows)
     (let* ((code-buf (get-buffer-create "*test-code-top*"))
diff --git a/tests/test-vterm-toggle--buffer-filter.el b/tests/test-vterm-toggle--buffer-filter.el
index 8deb9066..96681461 100644
--- a/tests/test-vterm-toggle--buffer-filter.el
+++ b/tests/test-vterm-toggle--buffer-filter.el
@@ -12,28 +12,19 @@
 (require 'ert)
 
 (add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+(add-to-list 'load-path (expand-file-name "tests" user-emacs-directory))
 (require 'eshell-vterm-config)
+(require 'testutil-vterm-buffers)
 
 (defun test-vterm-toggle--cleanup ()
-  "Kill any test-prefixed vterm-style buffers left behind."
-  (dolist (b (buffer-list))
-    (let ((name (buffer-name b)))
-      (when (or (string-prefix-p "*test-vterm" name)
-                (string-prefix-p "claude [" name))
-        (kill-buffer b)))))
-
-(defun test-vterm-toggle--make-vterm-buffer (name)
-  "Create BUFFER with vterm-mode for testing.
-Avoids actually launching a vterm process by manually setting major-mode."
-  (let ((buf (get-buffer-create name)))
-    (with-current-buffer buf
-      (setq-local major-mode 'vterm-mode))
-    buf))
+  "Kill leftover claude- and *test-vterm- prefixed buffers."
+  (cj/test--kill-claude-buffers)
+  (cj/test--kill-test-vterm-buffers))
 
 (ert-deftest test-vterm-toggle--buffer-p-accepts-vterm-mode ()
   "Normal: a vterm-mode buffer with non-claude name qualifies."
   (test-vterm-toggle--cleanup)
-  (let ((buf (test-vterm-toggle--make-vterm-buffer "*test-vterm-1*")))
+  (let ((buf (cj/test--make-fake-vterm-buffer "*test-vterm-1*")))
     (unwind-protect
         (should (cj/--vterm-toggle-buffer-p buf))
       (kill-buffer buf))))
@@ -41,7 +32,7 @@ Avoids actually launching a vterm process by manually setting major-mode."
 (ert-deftest test-vterm-toggle--buffer-p-rejects-claude ()
   "Boundary: claude-prefixed vterm buffers are excluded from F12's set."
   (test-vterm-toggle--cleanup)
-  (let ((buf (test-vterm-toggle--make-vterm-buffer "claude [project-a]")))
+  (let ((buf (cj/test--make-fake-vterm-buffer "claude [project-a]")))
     (unwind-protect
         (should-not (cj/--vterm-toggle-buffer-p buf))
       (kill-buffer buf))))
@@ -57,15 +48,15 @@ Avoids actually launching a vterm process by manually setting major-mode."
 (ert-deftest test-vterm-toggle--buffer-p-rejects-dead-buffer ()
   "Boundary: nil and dead buffers -> nil."
   (should-not (cj/--vterm-toggle-buffer-p nil))
-  (let ((buf (test-vterm-toggle--make-vterm-buffer "*test-vterm-dead*")))
+  (let ((buf (cj/test--make-fake-vterm-buffer "*test-vterm-dead*")))
     (kill-buffer buf)
     (should-not (cj/--vterm-toggle-buffer-p buf))))
 
 (ert-deftest test-vterm-toggle--buffers-filters-claude ()
   "Normal: returns vterm buffers but excludes claude-prefixed ones."
   (test-vterm-toggle--cleanup)
-  (let ((normal (test-vterm-toggle--make-vterm-buffer "*test-vterm-normal*"))
-        (claude (test-vterm-toggle--make-vterm-buffer "claude [for-test]")))
+  (let ((normal (cj/test--make-fake-vterm-buffer "*test-vterm-normal*"))
+        (claude (cj/test--make-fake-vterm-buffer "claude [for-test]")))
     (unwind-protect
         (let ((result (cj/--vterm-toggle-buffers)))
           (should (memq normal result))
@@ -76,7 +67,7 @@ Avoids actually launching a vterm process by manually setting major-mode."
 (ert-deftest test-vterm-toggle--displayed-window-finds-vterm ()
   "Normal: vterm in a window -> returns that window."
   (test-vterm-toggle--cleanup)
-  (let ((vt (test-vterm-toggle--make-vterm-buffer "*test-vterm-shown*")))
+  (let ((vt (cj/test--make-fake-vterm-buffer "*test-vterm-shown*")))
     (unwind-protect
         (save-window-excursion
           (delete-other-windows)
@@ -90,7 +81,7 @@ Avoids actually launching a vterm process by manually setting major-mode."
 (ert-deftest test-vterm-toggle--displayed-window-skips-claude ()
   "Boundary: only a claude vterm is displayed -> nil (claude not F12-managed)."
   (test-vterm-toggle--cleanup)
-  (let ((claude (test-vterm-toggle--make-vterm-buffer "claude [skip-test]")))
+  (let ((claude (cj/test--make-fake-vterm-buffer "claude [skip-test]")))
     (unwind-protect
         (save-window-excursion
           (delete-other-windows)
diff --git a/tests/test-vterm-toggle--dispatch.el b/tests/test-vterm-toggle--dispatch.el
index d63b3d35..93c06467 100644
--- a/tests/test-vterm-toggle--dispatch.el
+++ b/tests/test-vterm-toggle--dispatch.el
@@ -13,14 +13,9 @@
 (require 'cl-lib)
 
 (add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+(add-to-list 'load-path (expand-file-name "tests" user-emacs-directory))
 (require 'eshell-vterm-config)
-
-(defun test-vterm-toggle--dispatch-cleanup ()
-  "Kill any leftover test buffers."
-  (dolist (b (buffer-list))
-    (let ((name (buffer-name b)))
-      (when (string-prefix-p "*test-vterm" name)
-        (kill-buffer b)))))
+(require 'testutil-vterm-buffers)
 
 (ert-deftest test-vterm-toggle--dispatch-window-displayed-returns-toggle-off ()
   "Normal: displayed vterm window -> (toggle-off . WIN)."
@@ -32,7 +27,7 @@
 
 (ert-deftest test-vterm-toggle--dispatch-no-window-buffer-alive-returns-show-recent ()
   "Normal: no displayed vterm, at least one alive -> show-recent + first."
-  (test-vterm-toggle--dispatch-cleanup)
+  (cj/test--kill-test-vterm-buffers)
   (let ((b1 (get-buffer-create "*test-vterm-mru-1*"))
         (b2 (get-buffer-create "*test-vterm-mru-2*")))
     (unwind-protect
@@ -47,7 +42,7 @@
 
 (ert-deftest test-vterm-toggle--dispatch-no-window-no-buffer-returns-create-new ()
   "Boundary: nothing displayed, no alive vterms -> create-new."
-  (test-vterm-toggle--dispatch-cleanup)
+  (cj/test--kill-test-vterm-buffers)
   (cl-letf (((symbol-function 'cj/--vterm-toggle-displayed-window)
              (lambda (&optional _frame) nil))
             ((symbol-function 'cj/--vterm-toggle-buffers)
diff --git a/tests/testutil-vterm-buffers.el b/tests/testutil-vterm-buffers.el
new file mode 100644
index 00000000..864dd8f3
--- /dev/null
+++ b/tests/testutil-vterm-buffers.el
@@ -0,0 +1,38 @@
+;;; testutil-vterm-buffers.el --- Shared helpers for vterm/claude buffer tests -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; Cleanup helpers and a fake-vterm constructor used across the
+;; ai-vterm and vterm-toggle test files.  Before this module, each
+;; test file re-implemented the same `(dolist (b (buffer-list))
+;; (when (string-prefix-p ...) (kill-buffer b)))' loop with a
+;; different prefix.
+
+;;; Code:
+
+(defun cj/test--kill-buffers-matching-prefix (prefix)
+  "Kill all live buffers whose name starts with PREFIX."
+  (dolist (b (buffer-list))
+    (when (string-prefix-p prefix (buffer-name b))
+      (kill-buffer b))))
+
+(defun cj/test--kill-claude-buffers ()
+  "Kill all live buffers whose name matches the AI-vterm prefix \"claude [\"."
+  (cj/test--kill-buffers-matching-prefix "claude ["))
+
+(defun cj/test--kill-test-vterm-buffers ()
+  "Kill all live buffers whose name starts with \"*test-vterm\"."
+  (cj/test--kill-buffers-matching-prefix "*test-vterm"))
+
+(defun cj/test--make-fake-vterm-buffer (name)
+  "Return a buffer named NAME with `major-mode' set to `vterm-mode'.
+
+Avoids actually launching a vterm process by setting the mode
+buffer-locally.  Used by tests that need a buffer satisfying the
+vterm-mode predicate without the side-effects of `(vterm)'."
+  (let ((buf (get-buffer-create name)))
+    (with-current-buffer buf
+      (setq-local major-mode 'vterm-mode))
+    buf))
+
+(provide 'testutil-vterm-buffers)
+;;; testutil-vterm-buffers.el ends here