• Needs to use chai+mocha
• Needs assertion messages
• Should not fork 11 year old(!) translation
• Should not use Math.floor(Math.random()) nonsense, just do {random} = require 'lodash'
• Sample tests tests lack any form of structure
• Sample tests missing from full tests
• Sample tests cover much larger domain than full tests

test.check doesn't seem to be supported by codewars

Specifically, the author of the test used some bit manipulation to round, when he/she should have used Math.floor. The bit stuff only works with 32-bit integers. I myself submitted a solution with the same bug just to get the tests passing.