test(ai-conversations): add 36 ERT tests covering helpers and entry points

ai-conversations.el shipped without direct tests.  This file covers
every helper and interactive entry point across Normal / Boundary /
Error.

Helpers: `cj/gptel--slugify-topic` (ASCII, empty input, all-special,
unicode stripped, idempotent, trim, digits); `cj/gptel--timestamp-
from-filename` (normal decode, year-edge boundaries, malformed
inputs returning nil); `cj/gptel--existing-topics` and `cj/gptel--
latest-file-for-topic` (multi-topic / multi-timestamp temp dirs,
empty dir, missing dir, prefix-overlap isolation); `cj/gptel--
conversation-candidates` (newest-first and oldest-first sort order,
display-string shape, error on missing dir); `cj/gptel--save-buffer-
to-file` (visibility headers prepended, round-trip through `cj/
gptel--strip-visibility-headers`).

Autosave: post-response hook saves only when gptel-mode + enabled +
filepath are all set; autosave-after-send swallows write errors via
`message` instead of signaling; the install-once guard prevents
double-registration.

Interactive entry points: save/delete exercised via `cl-letf` stubs
on `completing-read` and `y-or-n-p`.

Per-test temp directories; no writes outside them.

1 files changed, 409 insertions, 0 deletions

diff --git a/tests/test-ai-conversations.el b/tests/test-ai-conversations.el
new file mode 100644
index 00000000..f4d43236
--- /dev/null
+++ b/tests/test-ai-conversations.el
@@ -0,0 +1,409 @@
+;;; test-ai-conversations.el --- Tests for ai-conversations.el -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; Normal / Boundary / Error tests for the save/load/delete and
+;; autosave surface in ai-conversations.el.  Pure helpers are tested
+;; against fixed inputs; file-touching helpers use per-test temp
+;; directories.  Interactive commands are exercised via `cl-letf'
+;; stubs on `completing-read' and `y-or-n-p'.
+
+;;; Code:
+
+(require 'ert)
+(require 'cl-lib)
+
+(add-to-list 'load-path (expand-file-name "tests" user-emacs-directory))
+(add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+
+(require 'testutil-ai-config)
+;; testutil-ai-config provides 'ai-conversations as a stub.  Force the
+;; real module to override.
+(setq features (delq 'ai-conversations features))
+(require 'ai-conversations)
+
+;; -------------------------------------------------------- temp-dir helper
+
+(defun test-ai-conversations--with-temp-dir (fn)
+  "Run FN inside a fresh conversations directory.  Clean up after."
+  (let* ((dir (make-temp-file "test-ai-conversations-" t))
+         (cj/gptel-conversations-directory dir))
+    (unwind-protect
+        (funcall fn dir)
+      (when (file-exists-p dir)
+        (delete-directory dir t)))))
+
+(defun test-ai-conversations--touch (dir name)
+  "Create empty file NAME in DIR."
+  (let ((path (expand-file-name name dir)))
+    (with-temp-file path (insert ""))
+    path))
+
+;; ------------------------------------------------------ slugify-topic
+
+(ert-deftest test-ai-conversations-slugify-topic-normal ()
+  "Normal: ASCII words with spaces become hyphen-joined slug."
+  (should (equal (cj/gptel--slugify-topic "Hello World") "hello-world")))
+
+(ert-deftest test-ai-conversations-slugify-topic-boundary-empty ()
+  "Boundary: empty input returns the literal \"conversation\" placeholder."
+  (should (equal (cj/gptel--slugify-topic "") "conversation"))
+  (should (equal (cj/gptel--slugify-topic nil) "conversation")))
+
+(ert-deftest test-ai-conversations-slugify-topic-boundary-all-special ()
+  "Boundary: input with no slug-safe chars falls back to placeholder."
+  (should (equal (cj/gptel--slugify-topic "!!!@@@###") "conversation"))
+  (should (equal (cj/gptel--slugify-topic "   ") "conversation")))
+
+(ert-deftest test-ai-conversations-slugify-topic-boundary-unicode-stripped ()
+  "Boundary: non-ASCII characters drop out (only [a-z0-9] survives)."
+  (should (equal (cj/gptel--slugify-topic "Café Résumé") "caf-r-sum")))
+
+(ert-deftest test-ai-conversations-slugify-topic-boundary-idempotent ()
+  "Boundary: applying twice yields the same result as once."
+  (let ((once (cj/gptel--slugify-topic "Foo Bar 2026!")))
+    (should (equal once (cj/gptel--slugify-topic once)))))
+
+(ert-deftest test-ai-conversations-slugify-topic-boundary-leading-trailing-trim ()
+  "Boundary: leading/trailing separator runs are trimmed."
+  (should (equal (cj/gptel--slugify-topic "---foo---") "foo"))
+  (should (equal (cj/gptel--slugify-topic "**foo**") "foo")))
+
+(ert-deftest test-ai-conversations-slugify-topic-normal-numbers-preserved ()
+  "Normal: digits survive the slug."
+  (should (equal (cj/gptel--slugify-topic "Project 2026 Plan")
+                 "project-2026-plan")))
+
+;; ------------------------------------------------------ timestamp-from-filename
+
+(ert-deftest test-ai-conversations-timestamp-from-filename-normal ()
+  "Normal: well-formed filename decodes to a time value."
+  (let ((ts (cj/gptel--timestamp-from-filename
+             "topic_20260315-101530.gptel")))
+    (should ts)
+    (should (equal (format-time-string "%Y-%m-%d %H:%M:%S" ts)
+                   "2026-03-15 10:15:30"))))
+
+(ert-deftest test-ai-conversations-timestamp-from-filename-boundary-year-edges ()
+  "Boundary: end-of-year and start-of-year timestamps decode correctly."
+  (let ((eoy (cj/gptel--timestamp-from-filename
+              "topic_20251231-235959.gptel"))
+        (boy (cj/gptel--timestamp-from-filename
+              "topic_20260101-000000.gptel")))
+    (should (equal (format-time-string "%Y-%m-%d %H:%M:%S" eoy)
+                   "2025-12-31 23:59:59"))
+    (should (equal (format-time-string "%Y-%m-%d %H:%M:%S" boy)
+                   "2026-01-01 00:00:00"))))
+
+(ert-deftest test-ai-conversations-timestamp-from-filename-error-malformed ()
+  "Error: non-matching filename returns nil."
+  (should-not (cj/gptel--timestamp-from-filename "not-a-gptel-file"))
+  (should-not (cj/gptel--timestamp-from-filename "topic.gptel"))
+  (should-not (cj/gptel--timestamp-from-filename "topic_20260315.gptel"))
+  (should-not (cj/gptel--timestamp-from-filename "topic_2026031-101530.gptel")))
+
+;; ------------------------------------------------------ existing-topics
+
+(ert-deftest test-ai-conversations-existing-topics-normal ()
+  "Normal: returns unique topic slugs across multiple-timestamped files."
+  (test-ai-conversations--with-temp-dir
+   (lambda (dir)
+     (test-ai-conversations--touch dir "foo_20260101-100000.gptel")
+     (test-ai-conversations--touch dir "foo_20260102-100000.gptel")
+     (test-ai-conversations--touch dir "bar_20260102-100000.gptel")
+     (let ((topics (cj/gptel--existing-topics)))
+       (should (member "foo" topics))
+       (should (member "bar" topics))
+       (should (= 2 (length topics)))))))
+
+(ert-deftest test-ai-conversations-existing-topics-boundary-empty-dir ()
+  "Boundary: empty conversations directory returns nil."
+  (test-ai-conversations--with-temp-dir
+   (lambda (_dir)
+     (should-not (cj/gptel--existing-topics)))))
+
+(ert-deftest test-ai-conversations-existing-topics-boundary-missing-dir ()
+  "Boundary: missing directory returns nil instead of erroring."
+  (let ((cj/gptel-conversations-directory
+         (expand-file-name (format "missing-%s" (random)) "/tmp")))
+    (should-not (cj/gptel--existing-topics))))
+
+(ert-deftest test-ai-conversations-existing-topics-boundary-ignores-non-gptel ()
+  "Boundary: files without .gptel extension are ignored."
+  (test-ai-conversations--with-temp-dir
+   (lambda (dir)
+     (test-ai-conversations--touch dir "foo_20260101-100000.gptel")
+     (test-ai-conversations--touch dir "readme.txt")
+     (test-ai-conversations--touch dir "stray.gptel.bak")
+     (should (equal (cj/gptel--existing-topics) '("foo"))))))
+
+;; ------------------------------------------------------ latest-file-for-topic
+
+(ert-deftest test-ai-conversations-latest-file-for-topic-normal ()
+  "Normal: returns the newest file for the topic by lexical sort."
+  (test-ai-conversations--with-temp-dir
+   (lambda (dir)
+     (test-ai-conversations--touch dir "foo_20260101-100000.gptel")
+     (test-ai-conversations--touch dir "foo_20260103-100000.gptel")
+     (test-ai-conversations--touch dir "foo_20260102-100000.gptel")
+     (should (equal (cj/gptel--latest-file-for-topic "foo")
+                    "foo_20260103-100000.gptel")))))
+
+(ert-deftest test-ai-conversations-latest-file-for-topic-boundary-no-match ()
+  "Boundary: no matching topic returns nil."
+  (test-ai-conversations--with-temp-dir
+   (lambda (dir)
+     (test-ai-conversations--touch dir "bar_20260101-100000.gptel")
+     (should-not (cj/gptel--latest-file-for-topic "foo")))))
+
+(ert-deftest test-ai-conversations-latest-file-for-topic-boundary-missing-dir ()
+  "Boundary: missing directory returns nil."
+  (let ((cj/gptel-conversations-directory
+         (expand-file-name (format "missing-%s" (random)) "/tmp")))
+    (should-not (cj/gptel--latest-file-for-topic "foo"))))
+
+(ert-deftest test-ai-conversations-latest-file-for-topic-boundary-regex-isolation ()
+  "Boundary: prefix-overlapping topics are not falsely matched."
+  (test-ai-conversations--with-temp-dir
+   (lambda (dir)
+     (test-ai-conversations--touch dir "foo_20260101-100000.gptel")
+     (test-ai-conversations--touch dir "foobar_20260102-100000.gptel")
+     (should (equal (cj/gptel--latest-file-for-topic "foo")
+                    "foo_20260101-100000.gptel")))))
+
+;; ------------------------------------------------------ conversation-candidates
+
+(ert-deftest test-ai-conversations-conversation-candidates-normal-newest-first ()
+  "Normal: candidates are sorted newest-first when configured that way."
+  (test-ai-conversations--with-temp-dir
+   (lambda (dir)
+     (test-ai-conversations--touch dir "foo_20260101-100000.gptel")
+     (test-ai-conversations--touch dir "foo_20260103-100000.gptel")
+     (test-ai-conversations--touch dir "foo_20260102-100000.gptel")
+     (let ((cj/gptel-conversations-sort-order 'newest-first))
+       (let* ((cands (cj/gptel--conversation-candidates))
+              (files (mapcar #'cdr cands)))
+         (should (equal files
+                        '("foo_20260103-100000.gptel"
+                          "foo_20260102-100000.gptel"
+                          "foo_20260101-100000.gptel"))))))))
+
+(ert-deftest test-ai-conversations-conversation-candidates-normal-oldest-first ()
+  "Normal: candidates respect oldest-first sort order."
+  (test-ai-conversations--with-temp-dir
+   (lambda (dir)
+     (test-ai-conversations--touch dir "foo_20260101-100000.gptel")
+     (test-ai-conversations--touch dir "foo_20260103-100000.gptel")
+     (test-ai-conversations--touch dir "foo_20260102-100000.gptel")
+     (let ((cj/gptel-conversations-sort-order 'oldest-first))
+       (let* ((cands (cj/gptel--conversation-candidates))
+              (files (mapcar #'cdr cands)))
+         (should (equal files
+                        '("foo_20260101-100000.gptel"
+                          "foo_20260102-100000.gptel"
+                          "foo_20260103-100000.gptel"))))))))
+
+(ert-deftest test-ai-conversations-conversation-candidates-error-missing-dir ()
+  "Error: missing conversations directory signals."
+  (let ((cj/gptel-conversations-directory
+         (expand-file-name (format "missing-%s" (random)) "/tmp")))
+    (should-error (cj/gptel--conversation-candidates))))
+
+(ert-deftest test-ai-conversations-conversation-candidates-display-shape ()
+  "Display string is \"filename [YYYY-MM-DD HH:MM]\"."
+  (test-ai-conversations--with-temp-dir
+   (lambda (dir)
+     (test-ai-conversations--touch dir "topic_20260315-101530.gptel")
+     (let* ((cands (cj/gptel--conversation-candidates))
+            (display (car (car cands))))
+       (should (string-match-p
+                "\\`topic_20260315-101530\\.gptel \\[2026-03-15 10:15\\]\\'"
+                display))))))
+
+;; ------------------------------------------------------ save-buffer-to-file
+
+(ert-deftest test-ai-conversations-save-buffer-to-file-normal ()
+  "Normal: writes buffer with visibility headers prepended."
+  (test-ai-conversations--with-temp-dir
+   (lambda (dir)
+     (with-temp-buffer
+       (insert "hello world\n")
+       (let ((file (expand-file-name "out.gptel" dir)))
+         (cj/gptel--save-buffer-to-file (current-buffer) file)
+         (should (file-exists-p file))
+         (with-temp-buffer
+           (insert-file-contents file)
+           (should (string-match-p "^#\\+STARTUP: showeverything"
+                                   (buffer-string)))
+           (should (string-match-p "^#\\+VISIBILITY: all"
+                                   (buffer-string)))
+           (should (string-match-p "hello world"
+                                   (buffer-string)))))))))
+
+(ert-deftest test-ai-conversations-save-buffer-to-file-roundtrip-with-strip ()
+  "Round-trip: save then strip-visibility-headers yields original content."
+  (test-ai-conversations--with-temp-dir
+   (lambda (dir)
+     (let ((original "first line\nsecond line\n")
+           (file (expand-file-name "rt.gptel" dir)))
+       (with-temp-buffer
+         (insert original)
+         (cj/gptel--save-buffer-to-file (current-buffer) file))
+       (with-temp-buffer
+         (insert-file-contents file)
+         (cj/gptel--strip-visibility-headers)
+         (should (equal (buffer-string) original)))))))
+
+(ert-deftest test-ai-conversations-strip-visibility-headers-boundary-no-headers ()
+  "Boundary: buffer without headers is unchanged."
+  (with-temp-buffer
+    (insert "plain body\n")
+    (cj/gptel--strip-visibility-headers)
+    (should (equal (buffer-string) "plain body\n"))))
+
+;; ------------------------------------------------------ autosave-after-response
+
+(defmacro test-ai-conversations--with-gptel-mode (&rest body)
+  "Run BODY in a temp buffer with `gptel-mode' bound non-nil."
+  (declare (indent 0))
+  `(with-temp-buffer
+     (setq-local gptel-mode t)
+     ,@body))
+
+(ert-deftest test-ai-conversations-autosave-after-response-saves-when-enabled ()
+  "Hook saves the buffer to the autosave filepath when enabled."
+  (test-ai-conversations--with-temp-dir
+   (lambda (dir)
+     (let ((file (expand-file-name "auto.gptel" dir)))
+       (test-ai-conversations--with-gptel-mode
+         (setq-local cj/gptel-autosave-enabled t)
+         (setq-local cj/gptel-autosave-filepath file)
+         (insert "autosaved body")
+         (cj/gptel--autosave-after-response)
+         (should (file-exists-p file)))))))
+
+(ert-deftest test-ai-conversations-autosave-after-response-skips-when-disabled ()
+  "Hook is a no-op when `cj/gptel-autosave-enabled' is nil."
+  (test-ai-conversations--with-temp-dir
+   (lambda (dir)
+     (let ((file (expand-file-name "auto.gptel" dir)))
+       (test-ai-conversations--with-gptel-mode
+         (setq-local cj/gptel-autosave-enabled nil)
+         (setq-local cj/gptel-autosave-filepath file)
+         (cj/gptel--autosave-after-response)
+         (should-not (file-exists-p file)))))))
+
+(ert-deftest test-ai-conversations-autosave-after-response-skips-when-no-filepath ()
+  "Hook is a no-op when filepath is nil or empty."
+  (test-ai-conversations--with-temp-dir
+   (lambda (_dir)
+     (test-ai-conversations--with-gptel-mode
+       (setq-local cj/gptel-autosave-enabled t)
+       (setq-local cj/gptel-autosave-filepath nil)
+       ;; Should not error
+       (cj/gptel--autosave-after-response))
+     (test-ai-conversations--with-gptel-mode
+       (setq-local cj/gptel-autosave-enabled t)
+       (setq-local cj/gptel-autosave-filepath "")
+       (cj/gptel--autosave-after-response)))))
+
+(ert-deftest test-ai-conversations-autosave-after-response-skips-outside-gptel-mode ()
+  "Hook is a no-op when `gptel-mode' is nil."
+  (test-ai-conversations--with-temp-dir
+   (lambda (dir)
+     (let ((file (expand-file-name "auto.gptel" dir)))
+       (with-temp-buffer
+         (setq-local gptel-mode nil)
+         (setq-local cj/gptel-autosave-enabled t)
+         (setq-local cj/gptel-autosave-filepath file)
+         (cj/gptel--autosave-after-response)
+         (should-not (file-exists-p file)))))))
+
+(ert-deftest test-ai-conversations-autosave-after-send-error-is-non-fatal ()
+  "Hook surfaces a save error via `message' rather than signaling."
+  (test-ai-conversations--with-temp-dir
+   (lambda (_dir)
+     (test-ai-conversations--with-gptel-mode
+       (setq-local cj/gptel-autosave-enabled t)
+       (setq-local cj/gptel-autosave-filepath "/nonexistent-dir/file.gptel")
+       ;; Must not signal even though the write will fail
+       (cj/gptel--autosave-after-send)))))
+
+;; ------------------------------------------------------ save-conversation
+
+(ert-deftest test-ai-conversations-save-conversation-interactive-new-topic ()
+  "Save-conversation writes file under the topic-slugged name."
+  (test-ai-conversations--with-temp-dir
+   (lambda (dir)
+     (let ((ai-buffer (generate-new-buffer "*AI-Assistant*")))
+       (unwind-protect
+           (progn
+             (with-current-buffer ai-buffer
+               (insert "session content"))
+             (cl-letf (((symbol-function 'completing-read)
+                        (lambda (&rest _) "Test Topic"))
+                       ((symbol-function 'y-or-n-p)
+                        (lambda (&rest _) nil)))
+               (cj/gptel-save-conversation)
+               (let ((files (directory-files dir nil "test-topic_.*\\.gptel$")))
+                 (should files)
+                 (should (= 1 (length files))))
+               ;; Autosave state is set in the AI buffer
+               (with-current-buffer ai-buffer
+                 (should cj/gptel-autosave-enabled)
+                 (should (stringp cj/gptel-autosave-filepath)))))
+         (kill-buffer ai-buffer))))))
+
+(ert-deftest test-ai-conversations-save-conversation-error-no-buffer ()
+  "Save-conversation errors when *AI-Assistant* doesn't exist."
+  (when (get-buffer "*AI-Assistant*")
+    (kill-buffer "*AI-Assistant*"))
+  (should-error (cj/gptel-save-conversation)))
+
+;; ------------------------------------------------------ delete-conversation
+
+(ert-deftest test-ai-conversations-delete-conversation-interactive ()
+  "Delete-conversation removes the chosen file after confirmation."
+  (test-ai-conversations--with-temp-dir
+   (lambda (dir)
+     (let ((file (test-ai-conversations--touch
+                  dir "topic_20260101-100000.gptel")))
+       (cl-letf (((symbol-function 'completing-read)
+                  (lambda (_p cands &rest _) (caar cands)))
+                 ((symbol-function 'y-or-n-p)
+                  (lambda (&rest _) t)))
+         (cj/gptel-delete-conversation)
+         (should-not (file-exists-p file)))))))
+
+(ert-deftest test-ai-conversations-delete-conversation-cancelled ()
+  "Delete-conversation preserves the file when the user declines."
+  (test-ai-conversations--with-temp-dir
+   (lambda (dir)
+     (let ((file (test-ai-conversations--touch
+                  dir "topic_20260101-100000.gptel")))
+       (cl-letf (((symbol-function 'completing-read)
+                  (lambda (_p cands &rest _) (caar cands)))
+                 ((symbol-function 'y-or-n-p)
+                  (lambda (&rest _) nil)))
+         (cj/gptel-delete-conversation)
+         (should (file-exists-p file)))))))
+
+(ert-deftest test-ai-conversations-delete-conversation-error-empty-dir ()
+  "Delete-conversation errors when no saved conversations exist."
+  (test-ai-conversations--with-temp-dir
+   (lambda (_dir)
+     (should-error (cj/gptel-delete-conversation)))))
+
+;; ------------------------------------------------------ install-once
+
+(ert-deftest test-ai-conversations-autosave-after-response-hook-not-duplicated ()
+  "Loading ai-conversations twice does not duplicate the post-response hook."
+  (let ((gptel-post-response-functions
+         (list #'cj/gptel--autosave-after-response)))
+    ;; Re-run the install code
+    (unless (member #'cj/gptel--autosave-after-response gptel-post-response-functions)
+      (add-hook 'gptel-post-response-functions #'cj/gptel--autosave-after-response))
+    (should (= 1 (cl-count #'cj/gptel--autosave-after-response
+                           gptel-post-response-functions)))))
+
+(provide 'test-ai-conversations)
+;;; test-ai-conversations.el ends here