I signed up. It gave me 2 emails. 1 saying I have an account. The second saying there was a problem setting up the account. Also using the first email left me to their site without being logged into my new account.
Personally this doesn't even look appealing.
The tests I took were looking like questions people hate to get on interviews: How does the prototype exactly work, will this exact code using this particular unused language feature result in an error, etc. During the React test I got asked questions about Webpack configuration keys!
Maybe I just took the wrong tests, let me know if there are any tests you'd deem fit for judging a candidate :-)
One more thing to use Pluralsight.
It may be interesting to have the quick skill assessment for brief measuring and the long version for more accurate measuring.
Good luck to you guys in adding new skill assessments.