According to the CISSP Common Body of Knowledge (CBK), there is no specific minimum frequency stipulated for testing a disaster recovery plan (DRP). However, it is recommended that DRPs should be tested regularly to ensure that they are effective and up-to-date. The frequency of testing should be based on the organization's business requirements, the stability of the environment, and the advice of the information security manager.
There are several industry standards and regulations that provide guidance on DRP testing frequency. For example, the National Institute of Standards and Technology (NIST) recommends that DRPs should be tested at least annually. The Payment Card Industry Data Security Standard (PCI DSS) requires annual testing of DRPs as well. However, these are only recommendations and actual testing frequency may vary depending on the organization's needs and risk appetite.