Parallel Testing Technique :

Usage	§ To ensure that the processing of new application (new version) is consistent with respect to the processing of previous application version.
Objectives	§ Conducting redundant processing to ensure that the new version or application performs correctly. § Demonstrating consistency and inconsistency between 2 versions of the application.
How to Use	§ Same input data should be run through 2 versions of same application system. § Parallel testing can be done with whole system or part of system (segment).
When to use	§ When there is uncertainty regarding correctness of processing of new application where the new and old version are similar. § In financial applications like banking where there are many similar applications the processing can be verified for old and new version through parallel testing.
Example	§ Operating new and old version of a payroll system to determine that the paychecks from both systems are reconcilable. § Running old version of application to ensure that the functions of old system are working fine with respect to the problems encountered in the new system.