High current capability, good integration in urban area and zero external magnetic field are advantages of HTS cables that make them interesting for implementation in the Netherlands. So far experience with HTS cable projects is good, but still limited. Yet there is a need for a proper testing practice. Due to limited operational experience, various aspects remain to be studied. This paper focuses on electrical testing of electrical insulation, the application of power laws and the length effect. These issues are yet to be resolved, but the paper discusses their background and uncertainties. This may give direction to the ongoing studies in order to assure quality of HTS.