Here a site to test this plugin, it's have a course, an activity with grade, and a certiticate
http://moodle-plungin-rc-bozoh.c9users.io/moodle
role | username | password
--------------------+---------------+-----------
Student | studenttest1 | STD-test-1
Student | studenttest2 | STD-test-2
Teacher | teachertest | TCH-test-1
Non editing teacher | teachertest2 | TCH-test-2
Powered by http://c9.io