Microservices testing: A systematic literature review

Context: Microservices offer scalability and resilience for modern cloud-native applications but present significant challenges in software testing due to their distributed and heterogeneous nature. Objective: This study aims to consolidate and classify the current body of knowledge on microservice testing through a systematic literature review, providing actionable insights for both researchers and practitioners. Methods: Following established guidelines for systematic literature reviews in software engineering, we identified 74 primary studies relevant to microservices testing. These studies were systematically categorized using the SWEBOK (Software Engineering Body of Knowledge) taxonomy for software testing. Specifically, we classified the identified techniques according to their testing objectives, levels, strategies, and types. We also evaluated the study types to gauge the maturity and readiness of the current state-of-the-art in microservice testing. Results: System testing emerged as the most frequently investigated testing level, followed by integration, unit, and acceptance testing. Conformance, regression, and API testing were the most common functional testing objectives, while performance efficiency and reliability were instead predominant in the case of non-functional testing. Specification-based testing strategies were the most adopted, followed by usage-based and fault-based ones. Additionally, most studies employed laboratory experiments and had low-to-medium technology readiness levels, indicating early-stage maturity. The systems under test varied in size and domain, with TrainTicket being the most widely used reference benchmark for large systems. Conclusion: While significant progress has been made in microservice testing, the field remains fragmented, with notable gaps in areas such as, e.g., flexibility and security testing. The dominance of early-stage proposals highlights the need for more empirical validation and industry-grade benchmarks to facilitate broader adoption. This review offers a structured roadmap for future research and practical adoption in microservices testing.