Comparing the results of requests processed against both the new and old system is a pattern. http://www.alwaysagileconsulting.com/application-pattern-verify-br

Comparing the results of requests processed against both the new and old system is a pattern. http://www.alwaysagileconsulting.com/application-pattern-verify-branch-by-abstraction/ http://www.alwaysagileconsulting.com/application-pattern-ver... It was also done in mainframes at the processor instruction level.