One of the expert-level challenges in API test automation is ensuring _________ when dealing with a large number of interconnected services.

One of the expert-level challenges in API test automation is ensuring robustness when dealing with a large number of interconnected services. In complex systems, APIs often rely on numerous interconnected services to function cohesively. Achieving robustness involves designing tests that account for the interdependencies between these services and validating the system's ability to handle various scenarios. This level of testing ensures the resilience of the entire system, making it a critical aspect of API test automation at an expert level.