Reconfigurable Intelligent Surfaces (RIS), based on metamaterials, are emerging as a key enabler of the 6G radio channel. These surfaces can dynamically manipulate electromagnetic waves, enabling control over reflection angles, beam shaping, and polarization — capabilities far beyond traditional specular reflection. This presentation explores how liquid crystal-based RIS can be designed, tested, and integrated into future wireless networks. We introduce essential concepts of RIS operation, followed by an in-depth look at key performance indicators (KPIs) in test and measurement. Two distinct over-the-air (OTA) test setups are presented, including 3D signal scans in anechoic chambers and signal quality metrics like EVM and directivity. We also discuss RIS deployment in cellular networks, focusing on its impact on the multipath environment and how this can be evaluated through coverage and channel sounding techniques. Finally, real-world measurement data from various RIS prototypes is shared to illustrate practical performance and testing insights, underlining the importance of qualification and certification for RIS in regulated 6G systems.