New Twiddle

controllers.application\.js

import Ember from 'ember';

export default Ember.Controller.extend({
    gotoSubroute: function(id) {
    },
  appName: 'Ember Twiddle',
  actions: {
    gotoSubroute: function(id) {
    }
  }
});

router\.js

import EmberRouter from '@ember/routing/router';
import config from './config/environment';

const Router = EmberRouter.extend({
  location: 'none',
  rootURL: config.rootURL
});

Router.map(function() {
  this.route('subroute', {path:'subroute/:subroute_id'});
});

export default Router;

routes.application\.js

import Ember from 'ember';

export default Ember.Route.extend({
  beforeModel: function() {
    // return new Ember.RSVP.Promise(function(resolve, reject) {
    //   Ember.run.later(resolve, 1000);
    // });
  },
    actions: {
    gotoSubroute: function(id) {
    }
  }
});

routes.subroute\.js

import Ember from 'ember';

export default Ember.Route.extend({
  
  model: function(params) {
    return 8;
  },
  afterModel: function() {
    return new Ember.RSVP.Promise(function(resolve, reject) {
      Ember.run.later(resolve, 3000);
    });
  }
});

templates.application-loading\.hbs

This is my application loading screen

templates.application\.hbs

<h1>Welcome to {{appName}}</h1>
{{#link-to 'subroute' 1}}Subroute{{/link-to}}
<br> 
<br>
{{outlet}}
<br>
<br>

templates.loading\.hbs

<h1>This is my loading screen</h1>

templates.subroute\.hbs

<h2> This is my subroute: {{model}} </h2>
{{#link-to "application"}}Application{{/link-to}}

tests.helpers.destroy-app\.js

import { run } from '@ember/runloop';

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

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.autoboot = true;
  attributes.rootElement = '#ember-testing';
  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 Application from '../app';
import config from '../config/environment';
import { setApplication } from '@ember/test-helpers';
import { start } from 'ember-qunit';
import { assign } from '@ember/polyfills';

let attributes = assign({ rootElement: '#main' }, config.APP);
setApplication(Application.create(attributes));

start();

twiddle\.json

{
  "version": "0.16.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.14.2",
    "ember-template-compiler": "3.14.3",
    "ember-testing": "3.14.3"
  } 
}