Software Testing Methodology Question:

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.
Examples " 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.