A disaster recovery test plan is a document that describes the methods and procedures for testing the effectiveness and readiness of a disaster recovery plan (DRP), which is a subset of a BCP that focuses on restoring the organization’s IT systems and data after a disruption or disaster. A disaster recovery test plan can have different types and levels of testing, depending on the objectives, scope, and resources of the organization. A parallel test is a type of disaster recovery test plan that involves activating the backup site and running the critical systems and processes in parallel with the primary site, without disrupting the normal operations. A parallel test is the most effective type of disaster recovery test plan, as it simulates a realistic scenario of a disruption or disaster, and allows the organization to evaluate the performance and functionality of the backup site, as well as the communication and coordination between the primary and backup sites. A parallel test also provides minimal risk, as it does not affect the normal operations of the primary site, and does not require switching over to the backup site. A read-through test is a type of disaster recovery test plan that involves reviewing the DRP document and verifying its accuracy and completeness, without performing any actual actions. A read-through test is the least effective type of disaster recovery test plan, as it does not test the actual implementation and execution of the DRP, and does not identify any potential issues or gaps in the DRP. A full interruption test is a type of disaster recovery test plan that involves shutting down the primary site and switching over to the backup site, and performing the normal operations from the backup site. A full interruption test is the most realistic type of disaster recovery test plan, as it tests the actual implementation and execution of the DRP, and identifies any potential issues or gaps in the DRP. However, a full interruption test also provides the highest risk, as it affects the normal operations of the primary site, and may cause data loss, downtime, or customer dissatisfaction. A simulation test is a type of disaster recovery test plan that involves simulating a disruption or disaster scenario and performing the actions and procedures of the DRP, without activating the backup site or affecting the normal operations. A simulation test is a moderately effective type of disaster recovery test plan, as it tests the implementation and execution of the DRP, and identifies any potential issues or gaps in the DRP. However, a simulation test also provides moderate risk, as it does not test the performance and functionality of the backup site, and may not simulate a realistic scenario of a disruption or disaster. References: [Disaster Recovery Test Plan], [CISSP All-in-One Exam Guide, Eighth Edition, Chapter 7: Security Operations]2