Working New Tests Template

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>
{{outlet}}
<br>
<br>

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.test-helper.js

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

setResolver(resolver);
start();

tests.unit.controllers.application-test.js

import { module, test } from 'qunit';
import { setupTest } from 'ember-qunit';

module('TODO: put something here', function(hooks) {
  setupTest(hooks);

  test('it exists', function(assert) {
    let controller = this.owner.lookup('controller:application');
    assert.ok(controller);
  });
});

twiddle.json

{
  "version": "0.15.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "ENV": {
    "APP": {
    }
  },
  "options": {
    "use_pods": false,
    "enable-testing": true
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.4.3",
    "ember-template-compiler": "3.4.3",
    "ember-testing": "3.4.3"
  },
  "addons": {
    "ember-data": "3.4.2"
  }
}