test-div-id-null

components.foo-bar.js

import Ember from 'ember';

export default Ember.Component.extend({
  tagName: '',
  
  init() {
    this._super();
    this.set('tagName', 'div');
  },
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle'
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{foo-bar class="test"}}
{{outlet}}
<br>
<br>

templates.components.foo-bar.hbs

foo-bar
{{yield}}

twiddle.json

{
  "version": "0.10.6",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "canary",
    "ember-data": "beta",
    "ember-template-compiler": "canary",
    "ember-testing": "canary"
  },
  "addons": {}
}