About skills.
There are, generally speaking, two complementary sources of certification:

1. one is the centralized authority, a social construct. Mankind has explicitly or implicitly worked for millenia on creating sources of authority but the problem of subversion and capture cannot be solved - people who are put in charge of the authority end up by subverting it to their own purposes and capturing the outcomes
2. at the opposite end is the "wisdom of the crowds", the decentralized source of certification: if a lot of people independently confirm that a person possesses a skill, that person's claim acquires credibility

Testing is a useful but not definitive means to quantify - tests can be devised by the authority or implicitly by the crowd. With a blockchain-backed platform that acts as an interface, if testing is offered then it might be perceived as though the Ressolid platform itself had become an authority. That might be appropriate in certain situations but needs to be considered carefully