Assessment as a Service is described from the perspective of adaptivity features in these systems. It is a modern e-Assessment system realized on cloud, integrating available interoperability features so it can extensively communicate with other Learning Management Systems (LMS) and use scalable cloud architecture capable to cope with increased workload. Adaptive control in eAssessment systems means to add features in test construction and test delivery, and can be realized with several AI and related methods. An example of such a system is the concept of online learning with adaptive testing, that exploits add on functionalities of a typical LMS with interactive, formative and integrative assessments used in the learning process. Such a system systematically asks questions and leads the students towards knowledge discovery as learning method.