Rejected: This translation only provides the answer for the kata, but it is missing the codes for the example test and actual test.

Best solution yet

this seems to be a valid issue still:
It should work for random inputs too - Expected: '517999.99999999994', instead got: '518000'

@HerrWert mentioned that 2 years ago, not as an issue though and it was overlooked.

...how many kata you need to complete to beat their score, by 1 point exactly.

Test.assertEquals(leaderB('ZozoFouchtra', 15991, 12000), "To beat ZozoFouchtra's score, I must complete 1330 Beta kata and 1 8kyu kata. Dammit!");

12000 + 1330 * 3 + 1 = 15991. I don't see how getting the same score as the other user is identical to "beating them by 1 point".

Report that as an issue, mark your post as having spoiler content (this a 7 kyu kata, but what you said can be abused) and state the language so a fix can be applied.

Thank you

If the score < 0, return 0.

Because of that.

Last of Sample Tests seems to be incorrect:
["b", "c", "b", "a"], ["", "a", "a", "c"]), 0
array2[0]=== "" - gives 0
array2[1]!== array1[1] - gives -1
array2[2]!== array1[2] - gives -1
array2[3]!== array1[3] - gives -1
the sum shoud be -3 (0-1-1-1).
Colud you please state why it is 0 not -3?

your code 2 * O(n) ...

Solved by retirement (also the OP said random tests were not that important here).

I've just realized that random tests are not important in this case. As the main task of the kata is to "solve it with (at most?) 1 method" - this requirement should be tested, not solution's behavior. If you can write good enough fixed tests, it should be alright.