It would be good to add tests with random inputs

that's correct

'123220'.to_i(6)
# => 11100

sorry, my bad.
Everything is ok with that!

Seems to be example with code '0"!dlroW ,olleH">:#,_@' is broken/not valid

Have you thought about adding tests with random entries?

Test case examples (section "Your Test Cases:") in Ruby have syntax errors:
You have missed a block (do-end) for each describe

I got the same. The last one in Example test cases is invalid, assuming that Kata Test Cases are valid.

No problem, you are welcome.
I'm glad that you have figured this problem out.

Translation in Ruby added
http://www.codewars.com/kata/typer-dot-js/translations

Thanks for checking!

About random tests - it should work if you have defined it as like
You were getting Float numbers by rand(10). That's why you got NoMethodError.

Please take a look at my "suggestion post".

No, there are tests that check
One of the tests expects:

find_the_ball(1, []) == 0

Another one (in the section "Testing with 10 cups"):

find_the_ball(1, []) != 0

However, my solution passed 6 tests.