Testing is an essential factor in the development of software and is considered even more relevant in microservices and API configurations. These approaches of modern architecture provide lots of advantages for scalability, flexibility, and maintainability, yet they present new questions about the system’s reliability and effective performance. In this chapter, we will explain why testing is important in microservices and API environments by introducing the main difficulties that developers and testers face, and then we will explore how AI techniques can transform the testing world.