nested generators

controllers.application.js

import Ember from 'ember';
import { task } from 'ember-concurrency';

function* fetchStuff() {
  console.log('In fetchStuff'); 
  yield fetchMoreStuffGeneratorFn();
  // fetchMoreStuff();
}

function* fetchMoreStuffGeneratorFn() {
  console.log('In fetchMoreStuffGeneratorFn');
}

function fetchMoreStuff() {
  console.log('In fetchMoreStuff');
}

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  
	fetchData: task(fetchStuff),
	
  actions: {
    myTask() {
      this.get('fetchData').perform(); 
    }
  }  
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<button onClick={{action 'myTask'}}>Run my task</button>
<br>
<br>
{{outlet}}
<br>
<br>

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": "3.2.2",
    "ember-template-compiler": "3.2.2",
    "ember-testing": "3.2.2"
  },
  "addons": {
    "ember-data": "3.2.2",
    "ember-concurrency": "0.8.19"
  }
}