“Extended Reality” (XR) systems are advanced interactive systems such as Virtual Reality (VR) and Augmented Reality (AR) systems. They have emerged in various domains, ranging from entertainment, cultural heritage, to combat training and mission critical applications. The development and authoring of such systems is an iterative process that also includes quality assurance to make sure that the resulting systems are correct and delivering a high quality user experience. As the complexity of these systems keeps increasing, the XR industry now finds itself confronting a soaring engineering challenge: paradoxically, XR’s fine grained and high level of interactivity and realism make such systems very hard and expensive to test. The current XR authoring and development toolset poses no XR testing technology beyond rudimentary record and replay tools that only work for simple test scenarios. This project aims to build a novel verification and validation technology for XR systems based on techniques from AI to provide learning and reasoning over a virtual world. With this technology XR developers can deploy powerful test agents to automatically explore and test the correct parameters of their virtual worlds as they iteratively develop and refine them. In addition, user experience is an equally important aspect for all XR systems. We will therefore also develop socio-emotional AI to enable test agents to conduct automated assessment of the quality of user experience and parameterization by different demographic and socio economic types, such as male, female, young, and elderly.