* test/lisp/emacs-lisp/find-func-tests.el: New file (for bug#43393)

* lisp/emacs-lisp/ert-x.el (ert-simulate-keys): New macro.

* test/lisp/international/mule-tests.el
(mule-cmds--test-universal-coding-system-argument): Use it and enable
the test also in batch mode.

lisp/emacs-lisp/ert-x.el

@@ -177,6 +177,18 @@ test for `called-interactively' in the command will fail."
     (cl-assert (not unread-command-events) t)
     return-value))
 
+(defmacro ert-simulate-keys (keys &rest body)
+  "Execute BODY with KEYS as pseudo-interactive input."
+  (declare (debug t) (indent 1))
+  `(let ((unread-command-events
+          ;; Add some C-g to try and make sure we still exit
+          ;; in case something goes wrong.
+          (append ,keys '(?\C-g ?\C-g ?\C-g)))
+         ;; Tell `read-from-minibuffer' not to read from stdin when in
+         ;; batch mode.
+         (executing-kbd-macro t))
+     ,@body))
+
 (defun ert-run-idle-timers ()
   "Run all idle timers (from `timer-idle-list')."
   (dolist (timer (copy-sequence timer-idle-list))