JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/mocha/2.2.5/mocha.min.css">
<script src="https://cdnjs.cloudflare.com/ajax/libs/mocha/2.2.5/mocha.min.js"></script>
<script src="https://rawgit.com/gampleman/quick_check.js/master/dist/jasmine-quick-check.js"></script>
<div id="mocha"></div>

JavaScript

mocha.setup('bdd'); //tell mocha which interface you are using

function sort(list) {
  for (var j = 1; j < list.length; j++) {
    var key = list[j],
        i = j - 1;
    while (i >= 0 && list[i] > key) {
      list[i + 1] = list[i];
      i--;
    }
    list[i + 1] = key;
  }
  return list;
}

describe('sort', function () { //describe unit of code to test
    it('array is same length', function() {
        qc.forAll(qc.arrayOf(qc.int), function(list) {
            var orig = list.slice(),
                sorted = sort(list);
            if (orig.length !== sorted.length) {
                throw "Sort failed on example " + JSON.stringify(orig);
            }
        });
    });
});

mocha.run();