Nice use of Array#cycle!

That's great! What's the problem?

Let's try and avoid victim blaming and focus on the cheaters, rather than those who want to share what they've learnt.

The most elegant solution IMO is to let the community decide by flagging cheating solutions.
If a solution receives enough flags, the submitter loses honour and the solution is faded out.
It would need to be carefully designed so the emphasis is on the solution, not the person.

If someone goes out of their way to cheat and avoid detection, let them be. Honour on the website does not reflect honour in real life.

Oops, sorry @GiacomoSorbi. I meant to reply to the kata author but put my comment in the wrong place.
I don't use CodeWars often, still learning its UI :)

I've also contacted @Katbow BTW.

Enjoyable kata!

I'd like to improve the test output but I don't see any options for submitting patches. Could you apply the changes if I send them to you?

Test output can be improved.

Check the Ruby version (including patch level) with

puts "ruby #{RUBY_VERSION}p#{RUBY_PATCHLEVEL}"

At the time of writing, katas run in ruby 2.1.6p336

Would be nice to know the gem versions as well.

The last example test case is missing a closing parenthesis, which causes a syntax error when trying to run tests.

This may be the only recursive solution so far :|

This solution has the smallest amount of keystrokes from the code you're given.

Note that Array#index is an alias of Array#find_index. So really you could do list.find_index(&block) and that shows how silly this kata is.