Suggest alternative reason for ERT test duplication error

* lisp/emacs-lisp/ert.el (ert-set-test):
Amend error message; maybe the redefinition was caused by a file
loaded twice (bug#66782).

Suggested by Xiyue Deng.

1 files changed, 1 insertions, 1 deletions

diff --git a/lisp/emacs-lisp/ert.el b/lisp/emacs-lisp/ert.el
index d727bc94ec5..61d8341bdad 100644
--- a/lisp/emacs-lisp/ert.el
+++ b/lisp/emacs-lisp/ert.el
@@ -152,7 +152,7 @@ mode.")
   (when (and noninteractive (get symbol 'ert--test))
     ;; Make sure duplicated tests are discovered since the older test would
     ;; be ignored silently otherwise.
-    (error "Test `%s' redefined" symbol))
+    (error "Test `%s' redefined (or loaded twice)" symbol))
   (define-symbol-prop symbol 'ert--test definition)
   definition)