this test will not only tell you if your cron is not working but the state your email server is in and if your fully set up to send emails 
the higher your sender score the higher % of emails will land in inbox's 
the lower you will be marked as a spammer and get your emails banned from just about every email provider 

simply copy the email addy or change the front part to what ever you like 
ie   testmyemails@mail-tester.com
then go to admin panel and past into the invite friends in 
user / invite new members 
and send invite the the email address the go back the site and click the 

( then check your score ) button under where you got the email addy from 
and wait for the result 

Email Tester

hope this help some one