What both disaster recovery and business continuity have in common is the need for testing and verification that the testing actually accomplishes the goals of DR or BC. A regular test plan must be performed and evaluated for both DR and BC. Without regular testing, you will never know that the data you thought were backed up can actually be restored or that your failover data center will come online when a disaster strikes. If you do not test your DR and BC plans, your PKI organization will fail when it is needed most. Backups can and do fail occasionally. If you do not test restoring your backups, you will never know if the data will be available in a crisis situation.
Jeff Stapleton & W. Clay Epstein; Security without Obscurity: A Guide to PKI Operations