You can test send a reminder by going to Admin > Reminders and choosing "Timesheet Manager Approval" or "Broadcast" reminder.  Choose an Organization and/or Approval Group in order to reduce the number of email recipients.  When clicked, the Preview button will show you the users who will receive the email.  You can uncheck as many users as you want, so the test is only sent to people you want to test with.  Click the Send button to send the email.  If you use Broadcast reminder, you can update the broadcast message at Admin > Setup > E-mail Reminders to state that this is just a test email and can be ignored.

Click here to go to the Knowledge Center for the full article.