test(gptel-tools): cover the helpers across the five remaining tools

The gptel-tools files had zero direct coverage outside of
`update_text_file`, which landed with its rewrite earlier this
session.  This commit adds 52 tests across the five other tools.

For three of the tools the helpers were already top-level defuns
(`read_text_file`, `list_directory_files`, `move_to_trash`).  The
other two had their main bodies inlined into the `gptel-make-tool`
lambda -- I extracted them so the work is testable without mocking
gptel itself:

  read_buffer.el     -> `cj/read-buffer--get-content`
  write_text_file.el -> `cj/write-text-file--run` plus
                        `--validate-path`, `--backup-name`,
                        `--ensure-parent`

Test files, by tool:

- read_buffer.el          (5 tests):  normal, empty, buffer-object,
  text-property-stripping, missing buffer.
- write_text_file.el     (10 tests):  validate-path, backup-name
  shape, ensure-parent (creates missing / rejects unwritable), run
  with normal / overwrite / existing-no-overwrite / empty content /
  outside-home.
- read_text_file.el      (12 tests):  validate-file-path (normal +
  three error shapes), metadata plist shape, size limits (no-op /
  hard cap / warning bypass with no-confirm), binary detection
  (text vs null-byte), special-type EPUB and generic-binary paths.
- list_directory_files.el (15 tests):  mode-to-permissions (file /
  dir / executable), get-file-info (file / directory), extension
  filter (keep / drop / always-dir / nil-extension), format-file-
  entry, list-directory flat / recursive / error, format-output
  with and without files.
- move_to_trash.el       (10 tests):  unique-name (no conflict /
  conflict with timestamp / no-extension), validate-path (HOME / /tmp
  / outside / critical-dir / missing), perform on file and
  directory.

Each test file uses the same load-path / gptel-stub idiom
(`eval-and-compile` block, gptel stub when the real package isn't
available) so the byte-compile hook is happy.

1 files changed, 162 insertions, 0 deletions

diff --git a/tests/test-gptel-tools-list-directory-files.el b/tests/test-gptel-tools-list-directory-files.el
new file mode 100644
index 00000000..a91a7e79
--- /dev/null
+++ b/tests/test-gptel-tools-list-directory-files.el
@@ -0,0 +1,162 @@
+;;; test-gptel-tools-list-directory-files.el --- Tests for list_directory_files -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; Tests for the helpers in list_directory_files.el.
+
+;;; Code:
+
+(require 'ert)
+(require 'cl-lib)
+
+(eval-and-compile
+  (add-to-list 'load-path (expand-file-name "tests" user-emacs-directory))
+  (add-to-list 'load-path (expand-file-name "gptel-tools" user-emacs-directory))
+  (setq load-prefer-newer t)
+  (unless (featurep 'gptel)
+    (defvar gptel-tools nil)
+    (defun gptel-make-tool (&rest _args) nil)
+    (defun gptel-get-tool (&rest _args) nil)
+    (provide 'gptel)))
+
+(require 'list_directory_files)
+
+;; -------------------------- helpers
+
+(defun test-gptel-tools-list--with-tree (fn)
+  "Create a small directory tree, call FN with its root, clean up."
+  (let ((root (make-temp-file "test-gptel-tools-list-" t)))
+    (unwind-protect
+        (progn
+          (with-temp-file (expand-file-name "a.txt" root) (insert "a"))
+          (with-temp-file (expand-file-name "b.org" root) (insert "b"))
+          (make-directory (expand-file-name "sub" root))
+          (with-temp-file (expand-file-name "sub/c.txt" root) (insert "c"))
+          (funcall fn root))
+      (delete-directory root t))))
+
+;; -------------------------- mode-to-permissions
+
+(ert-deftest test-gptel-tools-list-mode-to-permissions-regular-file ()
+  "Mode 0644 on a regular file: -rw-r--r--."
+  (should (equal (list-directory-files--mode-to-permissions #o0644)
+                 "-rw-r--r--")))
+
+(ert-deftest test-gptel-tools-list-mode-to-permissions-directory ()
+  "Mode 0755 + dir bit: drwxr-xr-x."
+  (should (equal (list-directory-files--mode-to-permissions
+                  (logior #o40000 #o0755))
+                 "drwxr-xr-x")))
+
+(ert-deftest test-gptel-tools-list-mode-to-permissions-executable ()
+  "Mode 0700: -rwx------."
+  (should (equal (list-directory-files--mode-to-permissions #o0700)
+                 "-rwx------")))
+
+;; -------------------------- get-file-info
+
+(ert-deftest test-gptel-tools-list-get-file-info-success ()
+  "Success: returns a plist with :success t and metadata."
+  (test-gptel-tools-list--with-tree
+   (lambda (root)
+     (let ((info (list-directory-files--get-file-info
+                  (expand-file-name "a.txt" root))))
+       (should (plist-get info :success))
+       (should (numberp (plist-get info :size)))
+       (should (stringp (plist-get info :permissions)))))))
+
+(ert-deftest test-gptel-tools-list-get-file-info-directory ()
+  "Directory info: :is-directory is t."
+  (test-gptel-tools-list--with-tree
+   (lambda (root)
+     (let ((info (list-directory-files--get-file-info
+                  (expand-file-name "sub" root))))
+       (should (plist-get info :is-directory))))))
+
+;; -------------------------- filter-by-extension
+
+(ert-deftest test-gptel-tools-list-filter-by-extension-keeps-match ()
+  "Filter for txt keeps txt files."
+  (let* ((filter (list-directory-files--filter-by-extension "txt"))
+         (info '(:success t :path "/x/foo.txt" :is-directory nil)))
+    (should (funcall filter info))))
+
+(ert-deftest test-gptel-tools-list-filter-by-extension-drops-non-match ()
+  "Filter for txt drops non-txt files."
+  (let* ((filter (list-directory-files--filter-by-extension "txt"))
+         (info '(:success t :path "/x/foo.org" :is-directory nil)))
+    (should-not (funcall filter info))))
+
+(ert-deftest test-gptel-tools-list-filter-by-extension-always-keeps-directories ()
+  "Filter keeps directories regardless of extension."
+  (let* ((filter (list-directory-files--filter-by-extension "txt"))
+         (info '(:success t :path "/x/sub" :is-directory t)))
+    (should (funcall filter info))))
+
+(ert-deftest test-gptel-tools-list-filter-by-extension-no-extension-is-nil ()
+  "No extension produces a nil filter (i.e. no filtering)."
+  (should-not (list-directory-files--filter-by-extension nil)))
+
+;; -------------------------- format-file-entry
+
+(ert-deftest test-gptel-tools-list-format-file-entry-shape ()
+  "Formatted entry contains permissions, size, mtime, and relative path."
+  (let* ((info (list (cons :path "/home/u/foo.txt")
+                     (cons :permissions "-rw-r--r--")
+                     (cons :executable nil)
+                     (cons :size 42)
+                     (cons :last-modified (current-time))))
+         ;; Build as plist by flattening the cons list.
+         (info-plist (cl-loop for (k . v) in info append (list k v)))
+         (out (list-directory-files--format-file-entry info-plist "/home/u")))
+    (should (string-match-p "-rw-r--r--" out))
+    (should (string-match-p "foo.txt" out))))
+
+;; -------------------------- list-directory
+
+(ert-deftest test-gptel-tools-list-list-directory-flat ()
+  "Non-recursive listing returns only entries in the top level."
+  (test-gptel-tools-list--with-tree
+   (lambda (root)
+     (let* ((result (list-directory-files--list-directory root nil nil))
+            (files (plist-get result :files)))
+       (should files)
+       (let ((paths (mapcar (lambda (i) (plist-get i :path)) files)))
+         (should (cl-some (lambda (p) (string-match-p "/a\\.txt\\'" p)) paths))
+         (should-not (cl-some (lambda (p) (string-match-p "/c\\.txt\\'" p)) paths)))))))
+
+(ert-deftest test-gptel-tools-list-list-directory-recursive ()
+  "Recursive listing also returns sub-directory contents."
+  (test-gptel-tools-list--with-tree
+   (lambda (root)
+     (let* ((result (list-directory-files--list-directory root t nil))
+            (files (plist-get result :files))
+            (paths (mapcar (lambda (i) (plist-get i :path)) files)))
+       (should (cl-some (lambda (p) (string-match-p "/c\\.txt\\'" p)) paths))))))
+
+(ert-deftest test-gptel-tools-list-list-directory-error-not-a-directory ()
+  "Non-directory path returns errors entry."
+  (test-gptel-tools-list--with-tree
+   (lambda (root)
+     (let* ((result (list-directory-files--list-directory
+                     (expand-file-name "a.txt" root) nil nil))
+            (errors (plist-get result :errors)))
+       (should errors)))))
+
+;; -------------------------- format-output
+
+(ert-deftest test-gptel-tools-list-format-output-has-files-section ()
+  "Format-output includes a \"Found N file(s)\" line when files present."
+  (test-gptel-tools-list--with-tree
+   (lambda (root)
+     (let* ((result (list-directory-files--list-directory root nil nil))
+            (out (list-directory-files--format-output root result)))
+       (should (string-match-p "Found [0-9]+ file" out))))))
+
+(ert-deftest test-gptel-tools-list-format-output-empty ()
+  "Empty result: \"No files found\"."
+  (let ((out (list-directory-files--format-output
+              "/nowhere" '(:files nil :errors nil))))
+    (should (string-match-p "No files found" out))))
+
+(provide 'test-gptel-tools-list-directory-files)
+;;; test-gptel-tools-list-directory-files.el ends here