feat: Add copy-to-top and copy-to-bottom buffer methods with tests

Add two new methods to copy buffer content regions:
- cj/copy-to-bottom-of-buffer: copies from point to end of buffer
- cj/copy-to-top-of-buffer: copies from beginning of buffer to point

Reorganize copy operations under C-; b c submenu:
- C-; b c w: copy whole buffer
- C-; b c t: copy to top (beginning to point)
- C-; b c b: copy to bottom (point to end)

Other copy operations (buffer name, file path, file link) remain at
C-; b base level for quick access.

Add comprehensive ERT tests (22 tests total):
- test-custom-buffer-file-copy-to-bottom-of-buffer.el (11 tests)
- test-custom-buffer-file-copy-to-top-of-buffer.el (11 tests)
- Tests cover normal, boundary, and error cases including unicode,
  narrowing, whitespace, and read-only buffers

All tests pass.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

1 files changed, 186 insertions, 0 deletions

diff --git a/tests/test-custom-buffer-file-copy-to-top-of-buffer.el b/tests/test-custom-buffer-file-copy-to-top-of-buffer.el
new file mode 100644
index 00000000..0f09f26d
--- /dev/null
+++ b/tests/test-custom-buffer-file-copy-to-top-of-buffer.el
@@ -0,0 +1,186 @@
+;;; test-custom-buffer-file-copy-to-top-of-buffer.el --- Tests for cj/copy-to-top-of-buffer -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; Tests for the cj/copy-to-top-of-buffer function from custom-buffer-file.el
+;;
+;; This function copies all text from the beginning of the buffer to point
+;; to the kill ring without modifying the buffer.
+
+;;; 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-buffer-file)
+
+;;; Setup and Teardown
+
+(defun test-copy-to-top-setup ()
+  "Set up test environment."
+  (setq kill-ring nil))
+
+(defun test-copy-to-top-teardown ()
+  "Clean up test environment."
+  (setq kill-ring nil))
+
+;;; Normal Cases
+
+(ert-deftest test-custom-buffer-file-copy-to-top-of-buffer-normal-point-in-middle-copies-from-beginning ()
+  "Should copy from beginning to point when point in middle."
+  (test-copy-to-top-setup)
+  (unwind-protect
+      (with-temp-buffer
+        (insert "Line 1\nLine 2\nLine 3")
+        (goto-char (point-min))
+        (forward-line 2)  ; Point at start of "Line 3"
+        (let ((original-content (buffer-string)))
+          (cj/copy-to-top-of-buffer)
+          ;; Buffer should be unchanged
+          (should (equal (buffer-string) original-content))
+          ;; Kill ring should contain from beginning to point
+          (should (equal (car kill-ring) "Line 1\nLine 2\n"))))
+    (test-copy-to-top-teardown)))
+
+(ert-deftest test-custom-buffer-file-copy-to-top-of-buffer-normal-single-line-copies-partial ()
+  "Should copy partial line content from beginning to middle of line."
+  (test-copy-to-top-setup)
+  (unwind-protect
+      (with-temp-buffer
+        (insert "Hello World")
+        (goto-char (point-min))
+        (forward-char 5)  ; Point after "Hello"
+        (cj/copy-to-top-of-buffer)
+        (should (equal (buffer-string) "Hello World"))
+        (should (equal (car kill-ring) "Hello")))
+    (test-copy-to-top-teardown)))
+
+;;; Boundary Cases
+
+(ert-deftest test-custom-buffer-file-copy-to-top-of-buffer-boundary-point-at-end-copies-all ()
+  "Should copy entire buffer when point at end."
+  (test-copy-to-top-setup)
+  (unwind-protect
+      (with-temp-buffer
+        (insert "Line 1\nLine 2\nLine 3")
+        (goto-char (point-max))
+        (cj/copy-to-top-of-buffer)
+        (should (equal (buffer-string) "Line 1\nLine 2\nLine 3"))
+        (should (equal (car kill-ring) "Line 1\nLine 2\nLine 3")))
+    (test-copy-to-top-teardown)))
+
+(ert-deftest test-custom-buffer-file-copy-to-top-of-buffer-boundary-point-at-beginning-copies-empty ()
+  "Should copy empty string when point at beginning."
+  (test-copy-to-top-setup)
+  (unwind-protect
+      (with-temp-buffer
+        (insert "Line 1\nLine 2\nLine 3")
+        (goto-char (point-min))
+        (cj/copy-to-top-of-buffer)
+        (should (equal (buffer-string) "Line 1\nLine 2\nLine 3"))
+        (should (equal (car kill-ring) "")))
+    (test-copy-to-top-teardown)))
+
+(ert-deftest test-custom-buffer-file-copy-to-top-of-buffer-boundary-empty-buffer-copies-empty ()
+  "Should copy empty string in empty buffer."
+  (test-copy-to-top-setup)
+  (unwind-protect
+      (with-temp-buffer
+        (cj/copy-to-top-of-buffer)
+        (should (equal (buffer-string) ""))
+        (should (equal (car kill-ring) "")))
+    (test-copy-to-top-teardown)))
+
+(ert-deftest test-custom-buffer-file-copy-to-top-of-buffer-boundary-point-at-second-char-copies-one ()
+  "Should copy first character when point at second character."
+  (test-copy-to-top-setup)
+  (unwind-protect
+      (with-temp-buffer
+        (insert "Hello")
+        (goto-char (1+ (point-min)))  ; After 'H'
+        (cj/copy-to-top-of-buffer)
+        (should (equal (buffer-string) "Hello"))
+        (should (equal (car kill-ring) "H")))
+    (test-copy-to-top-teardown)))
+
+(ert-deftest test-custom-buffer-file-copy-to-top-of-buffer-boundary-unicode-content-copies-correctly ()
+  "Should handle unicode content correctly."
+  (test-copy-to-top-setup)
+  (unwind-protect
+      (with-temp-buffer
+        (insert "Hello 👋\nمرحبا\nWorld")
+        (goto-char (point-min))
+        (forward-line 2)  ; Point at start of "World"
+        (cj/copy-to-top-of-buffer)
+        (should (equal (buffer-string) "Hello 👋\nمرحبا\nWorld"))
+        (should (equal (car kill-ring) "Hello 👋\nمرحبا\n")))
+    (test-copy-to-top-teardown)))
+
+(ert-deftest test-custom-buffer-file-copy-to-top-of-buffer-boundary-narrowed-buffer-respects-narrowing ()
+  "Should respect narrowing and only copy within narrowed region."
+  (test-copy-to-top-setup)
+  (unwind-protect
+      (with-temp-buffer
+        (insert "Line 1\nLine 2\nLine 3\nLine 4")
+        (goto-char (point-min))
+        (forward-line 1)
+        (let ((start (point)))
+          (forward-line 2)
+          (narrow-to-region start (point))
+          (goto-char (point-max))  ; Point at end of narrowed region
+          (cj/copy-to-top-of-buffer)
+          (should (equal (buffer-string) "Line 2\nLine 3\n"))
+          (should (equal (car kill-ring) "Line 2\nLine 3\n"))))
+    (test-copy-to-top-teardown)))
+
+(ert-deftest test-custom-buffer-file-copy-to-top-of-buffer-boundary-whitespace-only-copies-whitespace ()
+  "Should copy whitespace-only content."
+  (test-copy-to-top-setup)
+  (unwind-protect
+      (with-temp-buffer
+        (insert "   \n\t\t\n  ")
+        (goto-char (point-min))
+        (forward-char 7)  ; After second newline
+        (cj/copy-to-top-of-buffer)
+        (should (equal (buffer-string) "   \n\t\t\n  "))
+        (should (equal (car kill-ring) "   \n\t\t\n")))
+    (test-copy-to-top-teardown)))
+
+(ert-deftest test-custom-buffer-file-copy-to-top-of-buffer-boundary-single-character-copies-char ()
+  "Should copy single character buffer."
+  (test-copy-to-top-setup)
+  (unwind-protect
+      (with-temp-buffer
+        (insert "x")
+        (goto-char (point-max))
+        (cj/copy-to-top-of-buffer)
+        (should (equal (buffer-string) "x"))
+        (should (equal (car kill-ring) "x")))
+    (test-copy-to-top-teardown)))
+
+;;; Error Cases
+
+(ert-deftest test-custom-buffer-file-copy-to-top-of-buffer-error-read-only-buffer-succeeds ()
+  "Should work in read-only buffer since it doesn't modify content."
+  (test-copy-to-top-setup)
+  (unwind-protect
+      (with-temp-buffer
+        (insert "Read-only content")
+        (goto-char (point-max))
+        (read-only-mode 1)
+        (cj/copy-to-top-of-buffer)
+        (should (equal (car kill-ring) "Read-only content")))
+    (test-copy-to-top-teardown)))
+
+(provide 'test-custom-buffer-file-copy-to-top-of-buffer)
+;;; test-custom-buffer-file-copy-to-top-of-buffer.el ends here