Software quality assurance remains a cornerstone of reliable and maintainable software systems, particularly in the era of microservices and distributed architectures. Ensuring robustness requires a multi-faceted approach, combining defect classification, test suite reduction, contract testing, and secure communication protocols. This study synthesizes contemporary research and practical methodologies to address quality concerns in complex software-intensive systems. Drawing on frameworks for defect analysis, microservice anti-pattern identification, and empirical test suite reduction strategies, the article provides a comprehensive examination of techniques for maintaining high-quality software outcomes. Emphasis is placed on the role of automated testing, contract validation using tools like PACT, and the optimization of microservice communication through modified remote procedure calls and gRPC enhancements. Theoretical implications of action research in software engineering are explored to bridge gaps between empirical evidence and organizational practice. Additionally, the article delves into the application of information entropy and evolutionary clustering in test suite reduction, analyzing their impact on fault localization and execution cost efficiency. The discussion further evaluates the integration of security protocols, including mTLS, JWT, and RBAC, to safeguard distributed system interactions. Limitations and future research directions focus on scaling these methodologies to large, complex systems, as well as the balance between exhaustive testing and operational efficiency. By combining rigorous testing strategies with practical implementation insights, this work provides a holistic framework for enhancing both software quality and microservice reliability in contemporary development environments.