Mirage HasMany Issue

controllers.application.js

import Ember from 'ember';

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

mirage.config.js

import Mirage from 'ember-cli-mirage';

export default function() {
  window.server = this;
  
  this.get('/projects/:id');
};

mirage.factories.project.js

import { Factory } from 'ember-cli-mirage';

export default Factory.extend({
  name(i) {
    return `Project #${i}`;
  }
});

mirage.models.project.js

import { Model, hasMany } from 'ember-cli-mirage';

export default Model.extend({
  parents: hasMany('project')
});

models.project.js

import Model from "ember-data/model";
import attr from "ember-data/attr";
import { hasMany } from "ember-data/relationships";

export default Model.extend({
  name: attr('string'),
  parents: hasMany('project', { async: true }),
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{outlet}}
<br>
<br>

tests.acceptance.my-acceptance-test.js

import { test } from 'qunit';
import moduleForAcceptance from '../../tests/helpers/module-for-acceptance';

moduleForAcceptance('Testing the has many model generation');

test('testing has-many', function(assert) {
	let project1 = server.create('project'),
      project2 = server.create('project', {
        parents: [project1]
      });
  
  visit('/');
  
  getService('store').find('project', 2)
    .then(project => project.get('parents'))
  	.then(parents => {
        assert.equal(parents.get('length'), 1);
  	});
});

tests.helpers.destroy-app.js

import Ember from 'ember';

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

tests.helpers.get-service.js

import Em from 'ember';

export default Em.Test.registerHelper('getService', function(app, serviceName) {
    return app.__container__.lookup(`service:${serviceName}`);
});

tests.helpers.module-for-acceptance.js

import { module } from 'qunit';
import Ember from 'ember';
import startApp from '../helpers/start-app';
import destroyApp from '../helpers/destroy-app';

const { RSVP: { Promise } } = Ember;

export default function(name, options = {}) {
  module(name, {
    beforeEach() {
      this.application = startApp();

      if (options.beforeEach) {
        return options.beforeEach.apply(this, arguments);
      }
    },

    afterEach() {
      let afterEach = options.afterEach && options.afterEach.apply(this, arguments);
      return Promise.resolve(afterEach).then(() => destroyApp(this.application));
    }
  });
}

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';
import getService from './get-service';

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": "0.10.7",
  "ENV": {
    "ember-cli-mirage": {
      "enabled": true
    }
  },
  "EmberENV": {
    "FEATURES": {
      "ds-finder-include": true
    }
  },
  "options": {
    "use_pods": false,
    "enable-testing": true
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.10.0",
    "ember-data": "2.10.0",
    "ember-template-compiler": "2.10.0",
    "ember-testing": "2.10.0"
  },
  "addons": {
    "ember-cli-mirage": "0.3.0-beta.4"
  }
}