Exchange 2010 SP3 - Site Failover Test

I have a 2 site DAG (2 servers in primary and 1 in DR Site). FSW and Alt-FSW have been configured for potential need.

I have a requirement in which I need to regularly test the failover mechanism - to ensure all documentation and procedures are up to date. These test's need to be performed 'while' our primary site is still active and used by my users.

- Am I able to test the DR failover while my primary site is still operational?

(Do I stop the DR Exchange server using the -configurationonly setting in the Primary site?)

- Is there any issues when returning the DR back into the DAG in the primary site?

(Any issues with syncing of mailboxes?)

Thanks