test+fix:custom-file-buffer: add tests, fix linter warning

  Add 58 unit tests for buffer/file utility functions:
  - cj/copy-link-to-buffer-file (12 tests)
  - cj/copy-path-to-buffer-file-as-kill (12 tests)
  - cj/copy-whole-buffer (14 tests)
  - cj/clear-to-bottom-of-buffer (10 tests)
  - cj/clear-to-top-of-buffer (10 tests)

  Tests cover normal cases, boundary cases (unicode, empty buffers, narrowing,
  read-only buffers), and error cases.

  Production code change:
  - Fix linter warning: unused variable 'err' → '_' in cj/move-buffer-and-file

1 files changed, 209 insertions, 0 deletions

diff --git a/tests/test-custom-file-buffer-copy-link-to-buffer-file.el b/tests/test-custom-file-buffer-copy-link-to-buffer-file.el
new file mode 100644
index 00000000..94d1e01e
--- /dev/null
+++ b/tests/test-custom-file-buffer-copy-link-to-buffer-file.el
@@ -0,0 +1,209 @@
+;;; test-custom-file-buffer-copy-link-to-buffer-file.el --- Tests for cj/copy-link-to-buffer-file -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; Tests for the cj/copy-link-to-buffer-file function from custom-file-buffer.el
+;;
+;; This function copies the full file:// path of the current buffer's file to
+;; the kill ring. For non-file buffers, it does nothing (no error).
+
+;;; Code:
+
+(require 'ert)
+(require 'testutil-general)
+
+;; Add modules directory to load path
+(add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+
+;; Stub dependencies before loading the module
+(defvar cj/custom-keymap (make-sparse-keymap)
+  "Stub keymap for testing.")
+
+;; Stub ps-print package
+(provide 'ps-print)
+
+;; Now load the actual production module
+(require 'custom-file-buffer)
+
+;;; Setup and Teardown
+
+(defun test-copy-link-setup ()
+  "Set up test environment."
+  (setq kill-ring nil))
+
+(defun test-copy-link-teardown ()
+  "Clean up test environment."
+  ;; Kill all buffers visiting files in the test directory
+  (dolist (buf (buffer-list))
+    (when (buffer-file-name buf)
+      (when (string-prefix-p cj/test-base-dir (buffer-file-name buf))
+        (with-current-buffer buf
+          (set-buffer-modified-p nil)
+          (kill-buffer buf)))))
+  (cj/delete-test-base-dir)
+  (setq kill-ring nil))
+
+;;; Normal Cases
+
+(ert-deftest test-copy-link-simple-file ()
+  "Should copy file:// link for simple file buffer."
+  (test-copy-link-setup)
+  (unwind-protect
+      (let* ((test-dir (cj/create-test-subdirectory "test"))
+             (test-file (expand-file-name "test.txt" test-dir)))
+        (with-temp-file test-file
+          (insert "content"))
+        (with-current-buffer (find-file test-file)
+          (cj/copy-link-to-buffer-file)
+          (should (equal (car kill-ring) (concat "file://" test-file)))))
+    (test-copy-link-teardown)))
+
+(ert-deftest test-copy-link-non-file-buffer ()
+  "Should do nothing for non-file buffer without error."
+  (test-copy-link-setup)
+  (unwind-protect
+      (with-temp-buffer
+        (setq kill-ring nil)
+        (cj/copy-link-to-buffer-file)
+        (should (null kill-ring)))
+    (test-copy-link-teardown)))
+
+;;; Boundary Cases
+
+(ert-deftest test-copy-link-unicode-filename ()
+  "Should handle unicode in filename."
+  (test-copy-link-setup)
+  (unwind-protect
+      (let* ((test-dir (cj/create-test-subdirectory "test"))
+             (test-file (expand-file-name "café.txt" test-dir)))
+        (with-temp-file test-file
+          (insert "content"))
+        (with-current-buffer (find-file test-file)
+          (cj/copy-link-to-buffer-file)
+          (should (equal (car kill-ring) (concat "file://" test-file)))))
+    (test-copy-link-teardown)))
+
+(ert-deftest test-copy-link-spaces-in-filename ()
+  "Should handle spaces in filename."
+  (test-copy-link-setup)
+  (unwind-protect
+      (let* ((test-dir (cj/create-test-subdirectory "test"))
+             (test-file (expand-file-name "my file.txt" test-dir)))
+        (with-temp-file test-file
+          (insert "content"))
+        (with-current-buffer (find-file test-file)
+          (cj/copy-link-to-buffer-file)
+          (should (equal (car kill-ring) (concat "file://" test-file)))))
+    (test-copy-link-teardown)))
+
+(ert-deftest test-copy-link-special-chars-filename ()
+  "Should handle special characters in filename."
+  (test-copy-link-setup)
+  (unwind-protect
+      (let* ((test-dir (cj/create-test-subdirectory "test"))
+             (test-file (expand-file-name "[test]-(1).txt" test-dir)))
+        (with-temp-file test-file
+          (insert "content"))
+        (with-current-buffer (find-file test-file)
+          (cj/copy-link-to-buffer-file)
+          (should (equal (car kill-ring) (concat "file://" test-file)))))
+    (test-copy-link-teardown)))
+
+(ert-deftest test-copy-link-very-long-path ()
+  "Should handle very long path."
+  (test-copy-link-setup)
+  (unwind-protect
+      (let* ((test-dir (cj/create-test-subdirectory "test"))
+             (long-name (make-string 200 ?x))
+             (test-file (expand-file-name (concat long-name ".txt") test-dir)))
+        (with-temp-file test-file
+          (insert "content"))
+        (with-current-buffer (find-file test-file)
+          (cj/copy-link-to-buffer-file)
+          (should (equal (car kill-ring) (concat "file://" test-file)))))
+    (test-copy-link-teardown)))
+
+(ert-deftest test-copy-link-hidden-file ()
+  "Should handle hidden file."
+  (test-copy-link-setup)
+  (unwind-protect
+      (let* ((test-dir (cj/create-test-subdirectory "test"))
+             (test-file (expand-file-name ".hidden" test-dir)))
+        (with-temp-file test-file
+          (insert "content"))
+        (with-current-buffer (find-file test-file)
+          (cj/copy-link-to-buffer-file)
+          (should (equal (car kill-ring) (concat "file://" test-file)))))
+    (test-copy-link-teardown)))
+
+(ert-deftest test-copy-link-no-extension ()
+  "Should handle file with no extension."
+  (test-copy-link-setup)
+  (unwind-protect
+      (let* ((test-dir (cj/create-test-subdirectory "test"))
+             (test-file (expand-file-name "README" test-dir)))
+        (with-temp-file test-file
+          (insert "content"))
+        (with-current-buffer (find-file test-file)
+          (cj/copy-link-to-buffer-file)
+          (should (equal (car kill-ring) (concat "file://" test-file)))))
+    (test-copy-link-teardown)))
+
+(ert-deftest test-copy-link-symlink-file ()
+  "Should use buffer's filename for symlink."
+  (test-copy-link-setup)
+  (unwind-protect
+      (let* ((test-dir (cj/create-test-subdirectory "test"))
+             (target-file (expand-file-name "target.txt" test-dir))
+             (link-file (expand-file-name "link.txt" test-dir)))
+        (with-temp-file target-file
+          (insert "content"))
+        (make-symbolic-link target-file link-file)
+        (with-current-buffer (find-file link-file)
+          (cj/copy-link-to-buffer-file)
+          ;; Should use the link name (what buffer-file-name returns)
+          (should (equal (car kill-ring) (concat "file://" (buffer-file-name))))))
+    (test-copy-link-teardown)))
+
+(ert-deftest test-copy-link-kill-ring-has-content ()
+  "Should add to kill ring when it already has content."
+  (test-copy-link-setup)
+  (unwind-protect
+      (let* ((test-dir (cj/create-test-subdirectory "test"))
+             (test-file (expand-file-name "test.txt" test-dir)))
+        (with-temp-file test-file
+          (insert "content"))
+        (kill-new "existing content")
+        (with-current-buffer (find-file test-file)
+          (cj/copy-link-to-buffer-file)
+          (should (equal (car kill-ring) (concat "file://" test-file)))
+          (should (equal (cadr kill-ring) "existing content"))))
+    (test-copy-link-teardown)))
+
+(ert-deftest test-copy-link-empty-kill-ring ()
+  "Should populate empty kill ring."
+  (test-copy-link-setup)
+  (unwind-protect
+      (let* ((test-dir (cj/create-test-subdirectory "test"))
+             (test-file (expand-file-name "test.txt" test-dir)))
+        (with-temp-file test-file
+          (insert "content"))
+        (setq kill-ring nil)
+        (with-current-buffer (find-file test-file)
+          (cj/copy-link-to-buffer-file)
+          (should (equal (car kill-ring) (concat "file://" test-file)))
+          (should (= (length kill-ring) 1))))
+    (test-copy-link-teardown)))
+
+(ert-deftest test-copy-link-scratch-buffer ()
+  "Should do nothing for *scratch* buffer."
+  (test-copy-link-setup)
+  (unwind-protect
+      (progn
+        (setq kill-ring nil)
+        (with-current-buffer "*scratch*"
+          (cj/copy-link-to-buffer-file)
+          (should (null kill-ring))))
+    (test-copy-link-teardown)))
+
+(provide 'test-custom-file-buffer-copy-link-to-buffer-file)
+;;; test-custom-file-buffer-copy-link-to-buffer-file.el ends here