gistfile1.js

(function(root) { // Wrap our entire code in anyonmous function. Minimise your chance to leak scope into the global namespace. See last line.
  'use strict'; // http://stackoverflow.com/questions/1335851/what-does-use-strict-do-in-javascript-and-what-is-the-reasoning-behind-it

  var $ = root.$; // Convient access to the jQuery object. Chaining is expensive in JS.

  root.Search = (function() { // Wrap the entire class in an anonymous function. This guarantees we will not leak scope. We assign the class to the root object. In this case, window.
    function Search(el) { // Create a search object. This is also the constructor for the class.
      this.el = el;// Assign an ivar
    }

    Search.prototype.perform = function() { // Instance method
      // $ do something
    }

    return Search // Return the search object
  })();

  $(root.document).on('keyup', '#search', function() {
    new root.Search(this).perform();
  });
}).call(this); // `this` in a global context is always the root object. In the browser, it's window.

test('perform works as intended', function() {
  var search = new Search();
  ok(search);
});