The roles of hydropower plants within the energy system has been evolving during the last two decades. The potential to provide ancillary services to the grid is often harnessed, leading to a major change in hydropower plants operations. Ancillary services provision can nowadays be considered as one of the main functions of the power plant during the design of greenfield and refurbishment projects. Reduced scale physical model testing of hydraulic machines are meant to experimentally determine their main hydraulic performances. Model testing also provides a valuable opportunity to accurately gather information and to build models of the machine behavior that are of critical importance to fuel the transition of hydropower into the digital era triggered by some of the major industrial actors of the hydropower market. The quantities of interest within the scope of the guaranteed hydraulic performance are likely to be enriched following the new needs and expectations of the hydropower plants operators. The manufacturers also intend to deliver innovative digital solutions aside with their machines. This contextual breakthrough leads to supplementary requirements for future model testing campaigns that are not necessarily fully addressed within the current International Standards corpus, especially within the IEC 60193 International Standard referring to hydraulic turbines, storage pumps and pump-turbines model acceptance test. The purpose of this paper is to propose an outlook of the model testing beyond the scope of the IEC 60193 International Standard. Activities and techniques aiming at the characterization of the stability of the units, their transient behaviors and the machine condition within various operating modes and regimes are described. The maturity of the described practices is considered according to multiple points of view ranging from instrumentation and procedures to model vs. prototype transposition. The potential impact on the units operation is also discussed. A review of the outcomes from recent research and development projects is proposed together with their transfer into industrial practices. A reflection is also conducted about the foreseeable needs for model testing in the coming years, the gap with the existing state of the art and the envisioned paths to close it.