ember-data-service-belongsto-bug

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  actions: {
    setRelationships() {
      this.model.set('service', this.store.createRecord('service', { name: 'my service name' }));
      this.model.set('client', this.store.createRecord('client', { name: 'my client name' }));
    }
  },
});

models.appointment.js

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

export default Model.extend({
  service: belongsTo(),
  client: belongsTo(),
});

models.client.js

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

export default Model.extend({
  name: attr(),
  appointments: hasMany(),
});

models.service.js

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

export default Model.extend({
  name: attr(),
  appointments: hasMany(),
});

routes.application.js

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

export default Ember.Route.extend({
  model() {
  	return this.store.createRecord('appointment');
  }
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
<p><b>service name:</b> {{model.service.name}}</p>
<p><b>client name:</b> {{model.client.name}}</p>
<button {{action 'setRelationships'}}>Set Relationships</button>
{{outlet}}
<br>
<br>

tests.helpers.destroy-app.js

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

export default function destroyApp(application) {
  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';
import { start } from 'ember-cli-qunit';

setResolver(resolver);
start();

twiddle.json

{
  "version": "0.15.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.2.2",
    "ember-template-compiler": "3.2.2",
    "ember-testing": "3.2.2"
  },
  "addons": {
    "ember-data": "3.2.0"
  }
}