Improve image-tests.el Commentary

* test/src/image-tests.el: Doc fix; explain how to run from
command line.

1 files changed, 5 insertions, 2 deletions

diff --git a/test/src/image-tests.el b/test/src/image-tests.el
index 0a13db67d45..0b2d42ab9f2 100644
--- a/test/src/image-tests.el
+++ b/test/src/image-tests.el
@@ -22,8 +22,11 @@
 ;;; Commentary:
 
 ;; Most of these tests will only run in a GUI session, and not with
-;; "make check".  Run them manually in an interactive session with
-;; `M-x eval-buffer' followed by `M-x ert'.
+;; "make check".  You must run them manually in an interactive session
+;; with, for example, `M-x eval-buffer' followed by `M-x ert'.
+;;
+;; To run these tests from the command line, try:
+;;     ./src/emacs -Q -l test/src/image-tests.el -eval "(ert t)"
 
 ;;; Code: