What I normally do is pull spare DN's, and TN's, and build a complete test environment. ACD phone at my desk etc.
Build what you are looking for in Symposium, mail/CP etc. Build test phone with test queue, and start pegging calls.
It is important to not only 4 digit dial these tests, but make calls from outside of your environment, (cell phone, or 9+) to ensure customers will recieve the same treatment.
Change your out of hours range, so you can test call flow during and after hours. The after hours especially if you have some sort of mail treatment to test proper routing to mb's etc. Also make test calls to your phone when it is in Not ready/ make busy mode. This will test your RAN messages, and or MOH.