helper in controller

controllers.application.js

import Ember from 'ember';
import { myHelper } from '../helpers/my-helper';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  test: Ember.computed(function(){
    return myHelper();
  })
});

helpers.my-helper.js

import Ember from 'ember';

export function myHelper(params/*, hash*/) {
  return 'I am a HELPER!!!! Huzzah.';
}

export default Ember.Helper.helper(myHelper);

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{outlet}}
<br>
<br>
{{test}}

twiddle.json

{
  "version": "0.11.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.11.0",
    "ember-data": "2.11.0",
    "ember-template-compiler": "2.11.0",
    "ember-testing": "2.11.0"
  },
  "addons": {}
}