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.

1 files changed, 12 insertions, 21 deletions

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)