The benefits of the MPN can be found here - https://partner.microsoft.com/UK/program/programoverview/programdownloads/programguide

Internal use licenses can be found here - https://partner.microsoft.com/global/program/programoverview/40029254

ISV competency internal use additional benefits can be found here – https://partner.microsoft.com/global/program/competencies/isvsolutions/40011919

ISV competency s/w tests - https://partner.microsoft.com/40011374