2 files changed, 131 insertions, 3 deletions
diff --git a/tests/test-ai-config-gptel-magit-lazy-loading.el b/tests/test-ai-config-gptel-magit-lazy-loading.el
new file mode 100644
index 00000000..05e3634d
--- /dev/null
+++ b/tests/test-ai-config-gptel-magit-lazy-loading.el
@@ -0,0 +1,127 @@
+;;; test-ai-config-gptel-magit-lazy-loading.el --- Tests for gptel-magit lazy loading -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; Tests for the lazy gptel-magit integration in ai-config.el.
+;;
+;; ai-config.el uses `with-eval-after-load 'magit' to register autoloads
+;; and keybindings for gptel-magit functions.  This avoids loading gptel
+;; on every magit buffer (the old hook approach) and defers it until the
+;; user actually presses a gptel-magit key.
+;;
+;; Testing approach:
+;; - Load ai-config with gptel stubs (via testutil-ai-config) but WITHOUT
+;;   providing magit, so the eval-after-load block does not fire yet.
+;; - Provide a minimal magit stub (just the keymap and transient helpers),
+;;   which triggers the eval-after-load and wires up the bindings.
+;; - Verify that gptel-magit functions are registered as autoloads (not
+;;   fully loaded), confirming deferred loading works.
+;; - Verify the M-g keymap binding in git-commit-mode-map.
+;;
+;; What is NOT tested here (requires real magit transients):
+;; - transient-append-suffix actually adds "g" to magit-commit
+;; - transient-append-suffix actually adds "x" to magit-diff
+;; These are best verified manually in a running Emacs.
+
+;;; Code:
+
+(require 'ert)
+
+(add-to-list 'load-path (expand-file-name "tests" user-emacs-directory))
+(add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+
+;; Load gptel stubs — this does NOT provide 'magit, so the
+;; with-eval-after-load 'magit block in ai-config stays dormant.
+(require 'testutil-ai-config)
+
+;; Stub magit's keymap and transient infrastructure.  These must exist
+;; before we trigger the eval-after-load, since ai-config uses them to
+;; set up keybindings and transient entries.
+(defvar git-commit-mode-map (make-sparse-keymap)
+  "Stub keymap standing in for magit's git-commit-mode-map.")
+
+;; Stub transient-append-suffix to be a no-op.  We can't test transient
+;; integration without real magit transient definitions, so we just
+;; verify it doesn't error.
+(defvar test-gptel-magit--transient-calls nil
+  "Records calls to the stubbed transient-append-suffix for verification.")
+
+(defun transient-append-suffix (prefix loc suffix)
+  "Stub: record the call for test inspection instead of modifying transients.
+PREFIX is the transient being modified, LOC is the reference suffix,
+SUFFIX is the entry being appended."
+  (push (list prefix loc suffix) test-gptel-magit--transient-calls))
+
+;; Now load ai-config.  The with-eval-after-load 'magit block is
+;; registered but NOT executed yet.
+(require 'ai-config)
+
+;; ----------------------------- Setup / Teardown ------------------------------
+
+(defun test-gptel-magit-setup ()
+  "Trigger the magit eval-after-load by providing the feature.
+This simulates what happens when a user first opens magit."
+  (setq test-gptel-magit--transient-calls nil)
+  (provide 'magit))
+
+;; NOTE: We cannot un-provide 'magit between tests, and eval-after-load
+;; callbacks only fire once, so all tests share the same post-trigger
+;; state.  The setup runs once before the first test.
+
+(test-gptel-magit-setup)
+
+;;; Normal Cases — Autoloads
+
+(ert-deftest test-ai-config-gptel-magit-lazy-loading-normal-generate-message-is-autoload ()
+  "After magit loads, gptel-magit-generate-message should be an autoload.
+An autoload means the function is registered but gptel-magit.el has not
+been loaded yet — it will only load when the function is first called."
+  (should (fboundp 'gptel-magit-generate-message))
+  (should (autoloadp (symbol-function 'gptel-magit-generate-message))))
+
+(ert-deftest test-ai-config-gptel-magit-lazy-loading-normal-commit-generate-is-autoload ()
+  "After magit loads, gptel-magit-commit-generate should be an autoload."
+  (should (fboundp 'gptel-magit-commit-generate))
+  (should (autoloadp (symbol-function 'gptel-magit-commit-generate))))
+
+(ert-deftest test-ai-config-gptel-magit-lazy-loading-normal-diff-explain-is-autoload ()
+  "After magit loads, gptel-magit-diff-explain should be an autoload."
+  (should (fboundp 'gptel-magit-diff-explain))
+  (should (autoloadp (symbol-function 'gptel-magit-diff-explain))))
+
+;;; Normal Cases — Keymap Binding
+
+(ert-deftest test-ai-config-gptel-magit-lazy-loading-normal-keymap-binding ()
+  "M-g in git-commit-mode-map should be bound to gptel-magit-generate-message.
+This binding allows generating a commit message from the commit buffer."
+  (let ((bound (lookup-key git-commit-mode-map (kbd "M-g"))))
+    (should (eq bound 'gptel-magit-generate-message))))
+
+;;; Normal Cases — Transient Registration
+
+(ert-deftest test-ai-config-gptel-magit-lazy-loading-normal-transient-commit-registered ()
+  "transient-append-suffix should have been called for magit-commit.
+Verifies that the 'g' / Generate commit entry was registered."
+  (should (cl-find 'magit-commit test-gptel-magit--transient-calls
+                   :key #'car)))
+
+(ert-deftest test-ai-config-gptel-magit-lazy-loading-normal-transient-diff-registered ()
+  "transient-append-suffix should have been called for magit-diff.
+Verifies that the 'x' / Explain entry was registered."
+  (should (cl-find 'magit-diff test-gptel-magit--transient-calls
+                   :key #'car)))
+
+;;; Boundary Cases
+
+(ert-deftest test-ai-config-gptel-magit-lazy-loading-boundary-gptel-magit-not-loaded ()
+  "The gptel-magit feature should NOT be loaded after magit triggers.
+Only autoloads are registered — the actual package stays unloaded until
+a gptel-magit function is called."
+  (should-not (featurep 'gptel-magit)))
+
+(ert-deftest test-ai-config-gptel-magit-lazy-loading-boundary-exactly-two-transient-calls ()
+  "Exactly two transient-append-suffix calls should have been made.
+One for magit-commit (generate) and one for magit-diff (explain)."
+  (should (= 2 (length test-gptel-magit--transient-calls))))
+
+(provide 'test-ai-config-gptel-magit-lazy-loading)
+;;; test-ai-config-gptel-magit-lazy-loading.el ends here
diff --git a/tests/testutil-ai-config.el b/tests/testutil-ai-config.el
index 4839efd5..e8953389 100644
--- a/tests/testutil-ai-config.el
+++ b/tests/testutil-ai-config.el
@@ -63,9 +63,10 @@
 (defun gptel-prompts-add-update-watchers (&rest _) "Stub." nil)
 (provide 'gptel-prompts)
 
-;; Stub gptel-magit
-(defun gptel-magit-install (&rest _) "Stub." nil)
-(provide 'gptel-magit)
+;; NOTE: gptel-magit is NOT stubbed here.  ai-config.el now uses
+;; with-eval-after-load 'magit instead of use-package gptel-magit,
+;; so the magit integration only activates when magit is provided.
+;; See test-ai-config-gptel-magit-lazy-loading.el for magit stub tests.
 
 ;; Stub ai-conversations
 (provide 'ai-conversations)