Drive end-to-end testing across legacy and modernized systems, including retail payment flows, POS transactions, and settlement/reconciliation processes. Execute comprehensive testing covering POS devices, ISO 8583 message validation, payment authorization, and integration with external payment networks and FIS systems. Build and execute automation frameworks for functional, integration, regression, and performance testing, aligned with CI/CD pipelines. Validate transaction integrity, data consistency, and high-volume retail scenarios ensuring system reliability across in-store, mobile, and backend systems.