https://github.com/emberjs/ember.js/issues/9265

controllers.application.js

import Ember from 'ember';

var TestObject = Ember.Object.extend({
  value: "initial value",
  alias: Ember.computed.alias('value'),
  oneWay: Ember.computed.oneWay('value'),
  readOnly: Ember.computed.readOnly('value'),
  bool: Ember.computed.bool('value'),
  manual: Ember.computed('value', function () { return this.get('value'); }),
  computedDidChange: Ember.observer('alias', 'oneWay', 'readOnly', 'bool', 'manual', function (obj, key) {
    this.get('messages').push("Observer fired for: " + key);
  }),
  
  init() {
    this._super(...arguments);
    this.set('messages', []);
  }
});


export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  
  actions: {
    run() {
      let object = TestObject.create();
      object.set("value", "new value");
      this.set('object', object);
    }
  }
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
<button onclick={{action 'run'}}>run</button>
{{#each object.messages as |message|}}
	<br>{{message}}
{{/each}}
<br>
<br>

twiddle.json

{
  "version": "0.15.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.2.2",
    "ember-template-compiler": "3.2.2",
    "ember-testing": "3.2.2"
  },
  "addons": {
    "ember-data": "3.2.0"
  }
}