You might want to add Test.assertEquals(longestPalindrome("abcacba"), 7) as a test case. I've seen a solution which effectively iterates the array, for each character looks up the next index of of that character and decides if it's a palindrome -- this case will fail that method because it will only consider bcacb as a palindrome, since a -> a would only get the first half of the palindrome in the string.

module.js:457
throw err;
^

Error: Cannot find module './runners/elixir'
at Function.Module._resolveFilename (module.js:455:15)
at Function.Module._load (module.js:403:25)
at Module.require (module.js:483:17)
at require (internal/module.js:20:19)
at Object.module.exports.run (/runner/lib/runner.js:3:10)
at Object. (/runner/run-json.js:1:87)
at Module._compile (module.js:556:32)
at Object.Module._extensions..js (module.js:565:10)
at Module.load (module.js:473:32)
at tryModuleLoad (module.js:432:12)

This happens every time I want to submit or test my Elixir solution.