Ruby on Rails Tests

Hello,

I have a rather strange request: as a recruiter, I have to evaluate
the technical skills of some candidates for a RoR Developer position.
Unfortunately, I don't have a test suited for this competence, there
for, i need a source from where I can purchase such a test or one
where I can get it for free.

Thank you in advance for your response.

Have a good day.

Roxana Spînu