We write automated unit tests with JUnit to verify business logic and prevent regressions. JMeter is used for performance and load testing to ensure systems can handle production traffic volumes. Selenium provides automated browser-based testing for web applications. For payment systems, our testing extends to formal certification programmes — we have successfully completed EMVCo, Visa, Mastercard, American Express, Discover, and Borica certification for 3-D Secure v2.1.0 and v2.2.0 server modules. This combination of automated testing and industry-standard certification ensures that every deliverable meets both functional requirements and compliance standards.