Merge pull request sugarlabs#5057 from WillyEverGreen/test-rhythmruler-widget

test(rhythmruler): add unit tests for widget state and behavior

Author: omsuneri

js/widgets/rhythmruler.js

@@ -2846,3 +2846,6 @@ class RhythmRuler {
         }
     }
 }
+if (typeof module !== "undefined") {
+    module.exports = RhythmRuler;
+}