Need some pointers for WAS 7 Upgarde Testing. Our systems are being upgraded from WAS 6 to WAS 7. We need to ensure that their is no impact of the upgarde on the application functionality.

The application consist of enormous number of Webservices / Batches / and online UIs.

Please advise if there is any approach for performing tests on such an app for WAS 7 upgrade. The idea is to avoid complete Regression as the same is quite expensive in terms of time and cost.