gistfile1.js

function TestUser(){
  this.keyMap = {A:65, B:66, ENTER:14, LEFT:37, UP:38, RIGHT:39, DOWN:40};
}

TestUser.prototype.pressesKey = function(key){
  var e = jQuery.Event("keypress");
  e.keyCode = this.keyMap[key.toUpperCase()];
  
  $().trigger(e)
}

// -- using it

var user = new TestUser();
user.pressesKey('up');
user.pressesKey('left');