Clean mocking template

adapters.application.js

import DS from 'ember-data';

export default DS.JSONAPIAdapter.extend({
  namespace: 'api/v1'
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
});

mocks.js

export default function() {  
  getJSON('/api/v1/stations', stations);
}

function getJSON(url, jsonResponse) {
  $.mockjax({ url: url, responseText: jsonResponse });
}

let stations = {
  "data": [
    {
      "id": "15",
      "type": "stations",
      "attributes": {
        "name": "Test",
        "description": null,
        "slug": "test",
        "current_position": 1
      }
    }
  ]
}

models.station.js

import Model from 'ember-data/model';
import attr from 'ember-data/attr';
import { belongsTo, hasMany } from 'ember-data/relationships';

export default Model.extend({
});

routes.application.js

import Ember from 'ember';
import getMocks from '../mocks';

export default Ember.Route.extend({
  init() {
    this._super(...arguments);
    getMocks();
  },
  model() {
    return this.store.findAll('station');
  }
});

templates.application.hbs

<h1>Including relationship</h1>

{{model}}

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 = 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": "0.15.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.4.3",
    "ember-template-compiler": "3.4.3",
    "ember-testing": "3.4.3"
    "jquery-mockjax": "https://cdnjs.cloudflare.com/ajax/libs/jquery-mockjax/1.6.2/jquery.mockjax.js"
  },
  "addons": {
    "ember-data": "3.4.2"
  }
}