test:custom-file-buffer: add tests for cj/delete-buffer-and-file

  Add 36 unit tests for cj/delete-buffer-and-file covering:
  - Normal cases: VC vs non-VC file deletion, trash flag usage
  - Boundary cases: file content variations, naming edge cases, buffer states
  - Error cases: permission issues, VC failures, error propagation

  Key testing decisions documented in Commentary:
  - Mock delete-file errors for deterministic, portable tests
  - Test our code's behavior (branching logic, error propagation), not the
    underlying trash/filesystem implementations
  - Verify correct calls to vc-delete-file vs delete-file with trash flag

  All 36 tests passing.

1 files changed, 671 insertions, 0 deletions

diff --git a/tests/test-custom-file-buffer-delete-buffer-and-file.el b/tests/test-custom-file-buffer-delete-buffer-and-file.el
new file mode 100644
index 00000000..1c43ff3b
--- /dev/null
+++ b/tests/test-custom-file-buffer-delete-buffer-and-file.el
@@ -0,0 +1,671 @@
+;;; test-custom-file-buffer-delete-buffer-and-file.el --- Tests for cj/delete-buffer-and-file -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; Tests for the cj/delete-buffer-and-file function from custom-file-buffer.el
+;;
+;; This function deletes both the current buffer and the file it visits.
+;; It uses vc-delete-file for version-controlled files and delete-file
+;; for non-version-controlled files.
+;;
+;; Testing Strategy:
+;; - We test OUR code's behavior, not the underlying delete-file/vc-delete-file
+;;   implementations
+;; - We verify our code correctly:
+;;   1. Detects VC vs non-VC files (via vc-backend)
+;;   2. Calls the appropriate deletion function (vc-delete-file or delete-file)
+;;   3. Passes the trash flag (t) to delete-file
+;;   4. Propagates errors from the deletion functions
+;;
+;; Why We Mock delete-file Errors:
+;; - Tests like "already deleted file" and "no delete permission" are testing
+;;   system/environment behavior, not our code
+;; - The trash system handles these cases in environment-specific ways:
+;;   - Missing files may not error (trash handles gracefully)
+;;   - File permissions may not matter (directory permissions for moving to trash)
+;; - To make tests deterministic and portable, we mock delete-file to throw
+;;   specific errors, then verify our code propagates them correctly
+;; - This tests our contract: "when delete-file fails, we let the error through"
+
+;;; 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-delete-buffer-and-file-setup ()
+  "Setup for delete-buffer-and-file tests."
+  (cj/create-test-base-dir))
+
+(defun test-delete-buffer-and-file-teardown ()
+  "Teardown for delete-buffer-and-file tests."
+  ;; Kill all buffers visiting files in 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))
+
+;;; Normal Cases
+
+(ert-deftest test-delete-buffer-and-file-simple-delete ()
+  "Should delete file and kill buffer."
+  (test-delete-buffer-and-file-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"))
+        (find-file test-file)
+        (let ((buf (current-buffer)))
+          ;; Mock vc-backend to return nil (non-VC file)
+          (cl-letf (((symbol-function 'vc-backend) (lambda (&rest _) nil)))
+            (cj/delete-buffer-and-file)
+            (should-not (file-exists-p test-file))
+            (should-not (buffer-live-p buf)))))
+    (test-delete-buffer-and-file-teardown)))
+
+(ert-deftest test-delete-buffer-and-file-removes-file-from-disk ()
+  "Should remove file from disk."
+  (test-delete-buffer-and-file-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"))
+        (find-file test-file)
+        (cl-letf (((symbol-function 'vc-backend) (lambda (&rest _) nil)))
+          (cj/delete-buffer-and-file)
+          (should-not (file-exists-p test-file))))
+    (test-delete-buffer-and-file-teardown)))
+
+(ert-deftest test-delete-buffer-and-file-kills-buffer ()
+  "Should kill the buffer."
+  (test-delete-buffer-and-file-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"))
+        (find-file test-file)
+        (let ((buf (current-buffer)))
+          (cl-letf (((symbol-function 'vc-backend) (lambda (&rest _) nil)))
+            (cj/delete-buffer-and-file)
+            (should-not (buffer-live-p buf)))))
+    (test-delete-buffer-and-file-teardown)))
+
+(ert-deftest test-delete-buffer-and-file-calls-delete-file-with-trash-flag ()
+  "Should call delete-file with trash flag set to t."
+  (test-delete-buffer-and-file-setup)
+  (unwind-protect
+      (let* ((test-dir (cj/create-test-subdirectory "test"))
+             (test-file (expand-file-name "test.txt" test-dir))
+             (delete-file-args nil))
+        (with-temp-file test-file
+          (insert "content"))
+        (find-file test-file)
+        (cl-letf (((symbol-function 'vc-backend) (lambda (&rest _) nil))
+                  ((symbol-function 'delete-file)
+                   (lambda (file trash)
+                     (setq delete-file-args (list file trash)))))
+          (cj/delete-buffer-and-file)
+          (should (equal delete-file-args (list test-file t)))))
+    (test-delete-buffer-and-file-teardown)))
+
+(ert-deftest test-delete-buffer-and-file-shows-message ()
+  "Should display message for non-VC deletes."
+  (test-delete-buffer-and-file-setup)
+  (unwind-protect
+      (let* ((test-dir (cj/create-test-subdirectory "test"))
+             (test-file (expand-file-name "test.txt" test-dir))
+             (message-output nil))
+        (with-temp-file test-file
+          (insert "content"))
+        (find-file test-file)
+        (cl-letf (((symbol-function 'vc-backend) (lambda (&rest _) nil))
+                  ((symbol-function 'message)
+                   (lambda (fmt &rest args)
+                     (setq message-output (apply #'format fmt args)))))
+          (cj/delete-buffer-and-file)
+          (should (string-match-p "Deleted file.*test.txt" message-output))))
+    (test-delete-buffer-and-file-teardown)))
+
+(ert-deftest test-delete-buffer-and-file-vc-file-uses-vc-delete ()
+  "Should call vc-delete-file for VC files."
+  (test-delete-buffer-and-file-setup)
+  (unwind-protect
+      (let* ((test-dir (cj/create-test-subdirectory "test"))
+             (test-file (expand-file-name "test.txt" test-dir))
+             (vc-delete-called nil))
+        (with-temp-file test-file
+          (insert "content"))
+        (find-file test-file)
+        (cl-letf (((symbol-function 'vc-backend) (lambda (&rest _) 'Git))
+                  ((symbol-function 'vc-delete-file)
+                   (lambda (file)
+                     (setq vc-delete-called file)
+                     ;; Simulate vc-delete-file killing the buffer
+                     (when (get-file-buffer file)
+                       (kill-buffer (get-file-buffer file)))
+                     ;; Actually delete the file for test cleanup
+                     (delete-file file t))))
+          (cj/delete-buffer-and-file)
+          (should (string= vc-delete-called test-file))))
+    (test-delete-buffer-and-file-teardown)))
+
+(ert-deftest test-delete-buffer-and-file-non-vc-file-uses-delete-file ()
+  "Should call delete-file for non-VC files."
+  (test-delete-buffer-and-file-setup)
+  (unwind-protect
+      (let* ((test-dir (cj/create-test-subdirectory "test"))
+             (test-file (expand-file-name "test.txt" test-dir))
+             (delete-file-called nil))
+        (with-temp-file test-file
+          (insert "content"))
+        (find-file test-file)
+        (cl-letf (((symbol-function 'vc-backend) (lambda (&rest _) nil))
+                  ((symbol-function 'delete-file)
+                   (lambda (file trash)
+                     (setq delete-file-called file))))
+          (cj/delete-buffer-and-file)
+          (should (string= delete-file-called test-file))))
+    (test-delete-buffer-and-file-teardown)))
+
+(ert-deftest test-delete-buffer-and-file-returns-implicitly ()
+  "Should return result of last expression."
+  (test-delete-buffer-and-file-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"))
+        (find-file test-file)
+        (cl-letf (((symbol-function 'vc-backend) (lambda (&rest _) nil)))
+          (let ((result (cj/delete-buffer-and-file)))
+            ;; kill-buffer returns t, so result should be t
+            (should (eq result t)))))
+    (test-delete-buffer-and-file-teardown)))
+
+;;; Boundary Cases - File Content
+
+(ert-deftest test-delete-buffer-and-file-empty-file ()
+  "Should delete empty file."
+  (test-delete-buffer-and-file-setup)
+  (unwind-protect
+      (let* ((test-dir (cj/create-test-subdirectory "test"))
+             (test-file (expand-file-name "empty.txt" test-dir)))
+        (with-temp-file test-file)
+        (find-file test-file)
+        (cl-letf (((symbol-function 'vc-backend) (lambda (&rest _) nil)))
+          (cj/delete-buffer-and-file)
+          (should-not (file-exists-p test-file))))
+    (test-delete-buffer-and-file-teardown)))
+
+(ert-deftest test-delete-buffer-and-file-large-file ()
+  "Should delete large file."
+  (test-delete-buffer-and-file-setup)
+  (unwind-protect
+      (let* ((test-dir (cj/create-test-subdirectory "test"))
+             (test-file (expand-file-name "large.txt" test-dir))
+             (large-content (make-string 100000 ?x)))
+        (with-temp-file test-file
+          (insert large-content))
+        (find-file test-file)
+        (cl-letf (((symbol-function 'vc-backend) (lambda (&rest _) nil)))
+          (cj/delete-buffer-and-file)
+          (should-not (file-exists-p test-file))))
+    (test-delete-buffer-and-file-teardown)))
+
+(ert-deftest test-delete-buffer-and-file-binary-file ()
+  "Should delete binary file."
+  (test-delete-buffer-and-file-setup)
+  (unwind-protect
+      (let* ((test-dir (cj/create-test-subdirectory "test"))
+             (test-file (expand-file-name "binary.dat" test-dir))
+             (binary-content (string 0 1 2 3 255 254 253)))
+        (with-temp-file test-file
+          (set-buffer-multibyte nil)
+          (insert binary-content))
+        (find-file test-file)
+        (cl-letf (((symbol-function 'vc-backend) (lambda (&rest _) nil)))
+          (cj/delete-buffer-and-file)
+          (should-not (file-exists-p test-file))))
+    (test-delete-buffer-and-file-teardown)))
+
+(ert-deftest test-delete-buffer-and-file-with-unicode-content ()
+  "Should delete file with Unicode content."
+  (test-delete-buffer-and-file-setup)
+  (unwind-protect
+      (let* ((test-dir (cj/create-test-subdirectory "test"))
+             (test-file (expand-file-name "unicode.txt" test-dir))
+             (content "Hello 世界 مرحبا Привет"))
+        (with-temp-file test-file
+          (insert content))
+        (find-file test-file)
+        (cl-letf (((symbol-function 'vc-backend) (lambda (&rest _) nil)))
+          (cj/delete-buffer-and-file)
+          (should-not (file-exists-p test-file))))
+    (test-delete-buffer-and-file-teardown)))
+
+;;; Boundary Cases - File Naming
+
+(ert-deftest test-delete-buffer-and-file-unicode-filename ()
+  "Should delete file with Unicode filename."
+  (test-delete-buffer-and-file-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"))
+        (find-file test-file)
+        (cl-letf (((symbol-function 'vc-backend) (lambda (&rest _) nil)))
+          (cj/delete-buffer-and-file)
+          (should-not (file-exists-p test-file))))
+    (test-delete-buffer-and-file-teardown)))
+
+(ert-deftest test-delete-buffer-and-file-spaces-in-filename ()
+  "Should delete file with spaces in name."
+  (test-delete-buffer-and-file-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"))
+        (find-file test-file)
+        (cl-letf (((symbol-function 'vc-backend) (lambda (&rest _) nil)))
+          (cj/delete-buffer-and-file)
+          (should-not (file-exists-p test-file))))
+    (test-delete-buffer-and-file-teardown)))
+
+(ert-deftest test-delete-buffer-and-file-special-chars-filename ()
+  "Should delete file with special characters."
+  (test-delete-buffer-and-file-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"))
+        (find-file test-file)
+        (cl-letf (((symbol-function 'vc-backend) (lambda (&rest _) nil)))
+          (cj/delete-buffer-and-file)
+          (should-not (file-exists-p test-file))))
+    (test-delete-buffer-and-file-teardown)))
+
+(ert-deftest test-delete-buffer-and-file-hidden-file ()
+  "Should delete hidden file."
+  (test-delete-buffer-and-file-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"))
+        (find-file test-file)
+        (cl-letf (((symbol-function 'vc-backend) (lambda (&rest _) nil)))
+          (cj/delete-buffer-and-file)
+          (should-not (file-exists-p test-file))))
+    (test-delete-buffer-and-file-teardown)))
+
+(ert-deftest test-delete-buffer-and-file-no-extension ()
+  "Should delete file without extension."
+  (test-delete-buffer-and-file-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"))
+        (find-file test-file)
+        (cl-letf (((symbol-function 'vc-backend) (lambda (&rest _) nil)))
+          (cj/delete-buffer-and-file)
+          (should-not (file-exists-p test-file))))
+    (test-delete-buffer-and-file-teardown)))
+
+(ert-deftest test-delete-buffer-and-file-very-long-filename ()
+  "Should delete file with very long name."
+  (test-delete-buffer-and-file-setup)
+  (unwind-protect
+      (let* ((test-dir (cj/create-test-subdirectory "test"))
+             (long-name (concat (make-string 200 ?x) ".txt"))
+             (test-file (expand-file-name long-name test-dir)))
+        (with-temp-file test-file
+          (insert "content"))
+        (find-file test-file)
+        (cl-letf (((symbol-function 'vc-backend) (lambda (&rest _) nil)))
+          (cj/delete-buffer-and-file)
+          (should-not (file-exists-p test-file))))
+    (test-delete-buffer-and-file-teardown)))
+
+;;; Boundary Cases - Buffer State
+
+(ert-deftest test-delete-buffer-and-file-with-unsaved-changes ()
+  "Should handle buffer with unsaved changes."
+  (test-delete-buffer-and-file-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 "original"))
+        (find-file test-file)
+        (insert " modified")
+        (should (buffer-modified-p))
+        (let ((buf (current-buffer)))
+          (cl-letf (((symbol-function 'vc-backend) (lambda (&rest _) nil)))
+            (cj/delete-buffer-and-file)
+            (should-not (file-exists-p test-file))
+            (should-not (buffer-live-p buf)))))
+    (test-delete-buffer-and-file-teardown)))
+
+(ert-deftest test-delete-buffer-and-file-read-only-buffer ()
+  "Should handle read-only buffer."
+  (test-delete-buffer-and-file-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"))
+        (find-file test-file)
+        (read-only-mode 1)
+        (let ((buf (current-buffer)))
+          (cl-letf (((symbol-function 'vc-backend) (lambda (&rest _) nil)))
+            (cj/delete-buffer-and-file)
+            (should-not (file-exists-p test-file))
+            (should-not (buffer-live-p buf)))))
+    (test-delete-buffer-and-file-teardown)))
+
+(ert-deftest test-delete-buffer-and-file-multiple-windows ()
+  "Should work when buffer displayed in multiple windows."
+  (test-delete-buffer-and-file-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"))
+        (find-file test-file)
+        (delete-other-windows)
+        (split-window)
+        (other-window 1)
+        (switch-to-buffer (get-file-buffer test-file))
+        (let ((buf (current-buffer)))
+          (cl-letf (((symbol-function 'vc-backend) (lambda (&rest _) nil)))
+            (cj/delete-buffer-and-file)
+            (should-not (file-exists-p test-file))
+            (should-not (buffer-live-p buf))))
+        (delete-other-windows))
+    (test-delete-buffer-and-file-teardown)))
+
+(ert-deftest test-delete-buffer-and-file-buffer-not-current ()
+  "Should only operate on current buffer."
+  (test-delete-buffer-and-file-setup)
+  (unwind-protect
+      (let* ((test-dir (cj/create-test-subdirectory "test"))
+             (file1 (expand-file-name "file1.txt" test-dir))
+             (file2 (expand-file-name "file2.txt" test-dir)))
+        (with-temp-file file1
+          (insert "content1"))
+        (with-temp-file file2
+          (insert "content2"))
+        (find-file file1)
+        (find-file file2)
+        ;; Current buffer is file2
+        (cl-letf (((symbol-function 'vc-backend) (lambda (&rest _) nil)))
+          (cj/delete-buffer-and-file)
+          ;; file2 should be deleted, file1 should still exist
+          (should-not (file-exists-p file2))
+          (should (file-exists-p file1)))
+        (kill-buffer (get-file-buffer file1)))
+    (test-delete-buffer-and-file-teardown)))
+
+(ert-deftest test-delete-buffer-and-file-narrowed-buffer ()
+  "Should work with narrowed buffer."
+  (test-delete-buffer-and-file-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 "Line 1\nLine 2\nLine 3"))
+        (find-file test-file)
+        (goto-char (point-min))
+        (forward-line 1)
+        (narrow-to-region (point) (line-end-position))
+        (let ((buf (current-buffer)))
+          (cl-letf (((symbol-function 'vc-backend) (lambda (&rest _) nil)))
+            (cj/delete-buffer-and-file)
+            (should-not (file-exists-p test-file))
+            (should-not (buffer-live-p buf)))))
+    (test-delete-buffer-and-file-teardown)))
+
+;;; Error Cases - Buffer Issues
+
+(ert-deftest test-delete-buffer-and-file-non-file-buffer-does-nothing ()
+  "Should do nothing if buffer not visiting file."
+  (test-delete-buffer-and-file-setup)
+  (unwind-protect
+      (with-temp-buffer
+        (rename-buffer "non-file-buffer" t)
+        (let ((buf (current-buffer)))
+          (cj/delete-buffer-and-file)
+          ;; Buffer should still be alive
+          (should (buffer-live-p buf))))
+    (test-delete-buffer-and-file-teardown)))
+
+(ert-deftest test-delete-buffer-and-file-scratch-buffer-does-nothing ()
+  "Should do nothing for scratch buffer."
+  (test-delete-buffer-and-file-setup)
+  (unwind-protect
+      (with-current-buffer "*scratch*"
+        (cj/delete-buffer-and-file)
+        ;; Scratch buffer should still exist
+        (should (get-buffer "*scratch*")))
+    (test-delete-buffer-and-file-teardown)))
+
+(ert-deftest test-delete-buffer-and-file-already-killed-buffer ()
+  "Should error when operating on killed buffer."
+  (test-delete-buffer-and-file-setup)
+  (unwind-protect
+      (let* ((test-dir (cj/create-test-subdirectory "test"))
+             (test-file (expand-file-name "test.txt" test-dir))
+             (buf nil))
+        (with-temp-file test-file
+          (insert "content"))
+        (setq buf (find-file test-file))
+        (kill-buffer buf)
+        (should-error
+         (with-current-buffer buf
+           (cj/delete-buffer-and-file))))
+    (test-delete-buffer-and-file-teardown)))
+
+;;; Error Cases - File Issues
+
+(ert-deftest test-delete-buffer-and-file-already-deleted-file ()
+  "Should propagate error when delete-file fails on missing file."
+  (test-delete-buffer-and-file-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"))
+        (find-file test-file)
+        (cl-letf (((symbol-function 'vc-backend) (lambda (&rest _) nil))
+                  ((symbol-function 'delete-file)
+                   (lambda (file &optional _trash)
+                     (signal 'file-missing (list "Removing old name" "No such file or directory" file)))))
+          ;; Should propagate error from delete-file
+          (should-error (cj/delete-buffer-and-file) :type 'file-missing)))
+    (test-delete-buffer-and-file-teardown)))
+
+(ert-deftest test-delete-buffer-and-file-no-delete-permission ()
+  "Should propagate error when delete-file fails due to permissions."
+  (test-delete-buffer-and-file-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"))
+        (find-file test-file)
+        (cl-letf (((symbol-function 'vc-backend) (lambda (&rest _) nil))
+                  ((symbol-function 'delete-file)
+                   (lambda (file &optional _trash)
+                     (signal 'file-error (list "Removing old name" "Permission denied" file)))))
+          ;; Should propagate error from delete-file
+          (should-error (cj/delete-buffer-and-file) :type 'file-error)))
+    (test-delete-buffer-and-file-teardown)))
+
+(ert-deftest test-delete-buffer-and-file-no-write-permission-directory ()
+  "Should error if directory not writable."
+  (test-delete-buffer-and-file-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"))
+        (find-file test-file)
+        (set-file-modes test-dir #o555)
+        (cl-letf (((symbol-function 'vc-backend) (lambda (&rest _) nil)))
+          (should-error (cj/delete-buffer-and-file))
+          (set-file-modes test-dir #o755)))
+    (test-delete-buffer-and-file-teardown)))
+
+(ert-deftest test-delete-buffer-and-file-open-in-other-buffer ()
+  "Should handle file open in another buffer."
+  (test-delete-buffer-and-file-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"))
+        (find-file test-file)
+        (let ((buf1 (current-buffer)))
+          (find-file test-file)
+          (let ((buf2 (current-buffer)))
+            ;; Both buffers visiting same file
+            (should (eq buf1 buf2))
+            (cl-letf (((symbol-function 'vc-backend) (lambda (&rest _) nil)))
+              (cj/delete-buffer-and-file)
+              (should-not (file-exists-p test-file))
+              (should-not (buffer-live-p buf1))))))
+    (test-delete-buffer-and-file-teardown)))
+
+(ert-deftest test-delete-buffer-and-file-symlink-file ()
+  "Should handle symlink files."
+  (test-delete-buffer-and-file-setup)
+  (unwind-protect
+      (let* ((test-dir (cj/create-test-subdirectory "test"))
+             (real-file (expand-file-name "real.txt" test-dir))
+             (symlink (expand-file-name "link.txt" test-dir)))
+        (with-temp-file real-file
+          (insert "content"))
+        (make-symbolic-link real-file symlink)
+        (find-file symlink)
+        (cl-letf (((symbol-function 'vc-backend) (lambda (&rest _) nil)))
+          (cj/delete-buffer-and-file)
+          ;; Symlink should be deleted, real file should remain
+          (should-not (file-exists-p symlink))
+          (should (file-exists-p real-file))))
+    (test-delete-buffer-and-file-teardown)))
+
+(ert-deftest test-delete-buffer-and-file-symlink-directory ()
+  "Should handle files in symlinked directories."
+  (test-delete-buffer-and-file-setup)
+  (unwind-protect
+      (let* ((real-dir (cj/create-test-subdirectory "real"))
+             (link-dir (expand-file-name "link" cj/test-base-dir))
+             (test-file (expand-file-name "test.txt" real-dir)))
+        (with-temp-file test-file
+          (insert "content"))
+        (make-symbolic-link real-dir link-dir)
+        (let ((file-via-link (expand-file-name "test.txt" link-dir)))
+          (find-file file-via-link)
+          (cl-letf (((symbol-function 'vc-backend) (lambda (&rest _) nil)))
+            (cj/delete-buffer-and-file)
+            ;; File should be deleted
+            (should-not (file-exists-p test-file)))))
+    (test-delete-buffer-and-file-teardown)))
+
+;;; Edge Cases - Version Control
+
+(ert-deftest test-delete-buffer-and-file-git-tracked-file ()
+  "Should use vc-delete-file for git files."
+  (test-delete-buffer-and-file-setup)
+  (unwind-protect
+      (let* ((test-dir (cj/create-test-subdirectory "test"))
+             (test-file (expand-file-name "test.txt" test-dir))
+             (vc-delete-called nil))
+        (with-temp-file test-file
+          (insert "content"))
+        (find-file test-file)
+        (cl-letf (((symbol-function 'vc-backend) (lambda (&rest _) 'Git))
+                  ((symbol-function 'vc-delete-file)
+                   (lambda (file)
+                     (setq vc-delete-called t)
+                     (when (get-file-buffer file)
+                       (kill-buffer (get-file-buffer file)))
+                     (delete-file file t))))
+          (cj/delete-buffer-and-file)
+          (should vc-delete-called)))
+    (test-delete-buffer-and-file-teardown)))
+
+(ert-deftest test-delete-buffer-and-file-untracked-in-vc-repo ()
+  "Should use delete-file for untracked files in VC repo."
+  (test-delete-buffer-and-file-setup)
+  (unwind-protect
+      (let* ((test-dir (cj/create-test-subdirectory "test"))
+             (test-file (expand-file-name "untracked.txt" test-dir)))
+        (with-temp-file test-file
+          (insert "content"))
+        (find-file test-file)
+        ;; vc-backend returns nil for untracked files
+        (cl-letf (((symbol-function 'vc-backend) (lambda (&rest _) nil)))
+          (cj/delete-buffer-and-file)
+          (should-not (file-exists-p test-file))))
+    (test-delete-buffer-and-file-teardown)))
+
+(ert-deftest test-delete-buffer-and-file-vc-backend-detection ()
+  "Should correctly detect VC backend."
+  (test-delete-buffer-and-file-setup)
+  (unwind-protect
+      (let* ((test-dir (cj/create-test-subdirectory "test"))
+             (test-file (expand-file-name "test.txt" test-dir))
+             (backend-checked nil))
+        (with-temp-file test-file
+          (insert "content"))
+        (find-file test-file)
+        (cl-letf (((symbol-function 'vc-backend)
+                   (lambda (file)
+                     (setq backend-checked file)
+                     nil)))
+          (cj/delete-buffer-and-file)
+          (should (string= backend-checked test-file))))
+    (test-delete-buffer-and-file-teardown)))
+
+(ert-deftest test-delete-buffer-and-file-vc-delete-fails ()
+  "Should propagate vc-delete-file errors."
+  (test-delete-buffer-and-file-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"))
+        (find-file test-file)
+        (cl-letf (((symbol-function 'vc-backend) (lambda (&rest _) 'Git))
+                  ((symbol-function 'vc-delete-file)
+                   (lambda (file)
+                     (error "VC operation failed"))))
+          (should-error (cj/delete-buffer-and-file))))
+    (test-delete-buffer-and-file-teardown)))
+
+(provide 'test-custom-file-buffer-delete-buffer-and-file)
+;;; test-custom-file-buffer-delete-buffer-and-file.el ends here