Changing!

components.rugby-player.js

import Ember from 'ember';
const { computed } = Ember;

export default Ember.Component.extend({
  
  
  formattedName: computed("player.name", function() {
    const name = this.get("player.name");
    const number = this.get("player.number");
    
    return `#${number} - ${name}`;
  })
  
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({

    player: {
      name: "Rieko Ioane",
      number: 11
    }

});

templates.application.hbs

<h1>Format and Enter</h1>
<br> 
<br>
   {{rugby-player player=player}}
   
   Your player is: {{player.name}}
<br>
<br>

templates.components.rugby-player.hbs

Edit Rugby Player Name
<input 
  type="text"
  value={{formattedName}}
  oninput={{action (mut player.name) value="target.value"}}
 />

tests.helpers.destroy-app.js

import Ember from 'ember';

export default function destroyApp(application) {
  Ember.run(application, 'destroy');
}

tests.helpers.resolver.js

import Resolver from '../../resolver';
import config from '../../config/environment';

const resolver = Resolver.create();

resolver.namespace = {
  modulePrefix: config.modulePrefix,
  podModulePrefix: config.podModulePrefix
};

export default resolver;

tests.helpers.start-app.js

import Ember from 'ember';
import Application from '../../app';
import config from '../../config/environment';

const { run } = Ember;
const assign = Ember.assign || Ember.merge;

export default function startApp(attrs) {
  let application;

  let attributes = assign({rootElement: "#test-root"}, config.APP);
  attributes = assign(attributes, attrs); // use defaults, but you can override;

  run(() => {
    application = Application.create(attributes);
    application.setupForTesting();
    application.injectTestHelpers();
  });

  return application;
}

tests.test-helper.js

import resolver from './helpers/resolver';
import {
  setResolver
} from 'ember-qunit';

setResolver(resolver);

twiddle.json

{
  "version": "0.12.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.12.0",
    "ember-template-compiler": "2.12.0",
    "ember-testing": "2.12.0"
  },
  "addons": {
    "ember-data": "2.12.1"
  }
}