Instance initializer unit test fails with "store is undefined"

Question

After generating an example application:

ember new preloadtest
cd preloadtest/
ember g instance-initializer preload
ember g model test-data
ember g route index
ember g adapter application

With the following files:

models/test-data.js

import DS from 'ember-data';

export default DS.Model.extend({
  name: DS.attr('string'),
  value: DS.attr( 'number' )
});

routes/index.js

import Ember from 'ember';

export default Ember.Route.extend({
  model(){
    return this.store.peekAll( 'test-data' );
  }
});

instance-initializers/preload.js

export function initialize( appInstance ) {
  let store = appInstance.lookup( 'service:store' );
  store.pushPayload( { "testDatas": [
    { "id": 1, "name": "aaa", "value": 1},
    { "id": 2, "name": "bbb", "value": 2},
    { "id": 3, "name": "ccc", "value": 3}
  ] } );
}

export default {
  name: 'preload',
  initialize
};

templates/index.hbs

<ul>
{{#each model as |td|}}
  <li>{{td.name}}: {{td.value}}</li>
{{/each}}
</ul>

adapters/application.js

import RESTAdapter from 'ember-data/adapters/rest';

export default RESTAdapter.extend({});

ember serve runs the application and displays the preload data but going to /tests the default unit test for the preload instance initializer fails with the error store is undefined.

Full Error Message:

Died on test #1 @http://localhost:4200/assets/tests.js:212:1
Module.prototype.exports@http://localhost:4200/assets/vendor.js:94:20
Module.prototype.build@http://localhost:4200/assets/vendor.js:142:5
findModule@http://localhost:4200/assets/vendor.js:193:5
requireModule@http://localhost:4200/assets/vendor.js:181:12
TestLoader.prototype.require@http://localhost:4200/assets/test-loader.js:67:9
TestLoader.prototype.loadModules@http://localhost:4200/assets/test-loader.js:58:13
TestLoader.load@http://localhost:4200/assets/test-loader.js:89:7
@http://localhost:4200/assets/test-support.js:6397:5
: store is undefined@ 114 ms
Source:     

initialize@http://localhost:4200/assets/preloadtest.js:213:5
@http://localhost:4200/assets/tests.js:213:1
runTest@http://localhost:4200/assets/test-support.js:2716:14
Test.prototype.run@http://localhost:4200/assets/test-support.js:2701:4
run/<@http://localhost:4200/assets/test-support.js:2843:6
process@http://localhost:4200/assets/test-support.js:2502:4
begin@http://localhost:4200/assets/test-support.js:2484:2
resumeProcessing/<@http://localhost:4200/assets/test-support.js:2544:4

How do I initialize the application's store so that it can be used in the unit test?

Edit - tests/unit/instance-initializers/preload-test.js

import Ember from 'ember';
import { initialize } from 'preloadtest/instance-initializers/preload';
import { module, test } from 'qunit';
import destroyApp from '../../helpers/destroy-app';
//import DS from 'ember-data';

module('Unit | Instance Initializer | preload', {
  //needs: [ 'service:store' ],
  beforeEach: function() {
    Ember.run(() => {
      this.application = Ember.Application.create();
      this.appInstance = this.application.buildInstance();
    });
  },
  afterEach: function() {
    Ember.run(this.appInstance, 'destroy');
    destroyApp(this.application);
  }
});

// Replace this with your real tests.
test('it works', function(assert) {
  initialize(this.appInstance);

  // you would normally confirm the results of the initializer here
  assert.ok(true);
});

Tried it with needs: [ 'service:store' ] and without (although its suggested that you should not need to do this if Ember-Data is on the page - which I've also tried importing both in the unit test and in the instance initialiser).

Versions:

Ember      : 2.4.5
Ember Data : 2.5.2

Answer 1

At Unit test of an instance-initializer, you don't need to get real store service. In such cases, prefer using mock services. The behaviour of your instance-initializer is to put some data to the store which is provided by application. You can easily mock that store.

Example test code with mock service:

import Ember from 'ember';
import { initialize } from 'preloadtest/instance-initializers/preload';
import { module, test } from 'qunit';
import destroyApp from '../../helpers/destroy-app';

//this is the mock store service:
const storeStubFactory  = Ember.Service.extend({
  data: null,
  init(){
    this.data = [];
  },
  pushPayload(payload){
      this.get('data').pushObject(payload); 
  },
  getAllPayloads(){
      return this.get('data');
  }
});

module('Unit | Instance Initializer | preload', {
  beforeEach: function() {
    Ember.run(() => {
      this.application = Ember.Application.create();
      this.appInstance = this.application.buildInstance();
      //Register your mock service (do not  create instance, use factory)
      this.appInstance.register('service:store', storeStubFactory);
    });
  },
  afterEach: function() {
    Ember.run(this.appInstance, 'destroy');
    destroyApp(this.application);
  }
});

// This is your real test:
test('it works', function(assert) {
  initialize(this.appInstance);

  // confirm that mock service has the correct payload:      
  assert.ok(this.appInstance.lookup('service:store').getAllPayloads());
});

Second option

Of course you can also mock the appInstance paramater of the initialize function as below:

import Ember from 'ember';
import { initialize } from 'preloadtest/instance-initializers/preload';
import { module, test } from 'qunit';
import destroyApp from '../../helpers/destroy-app';

const storeStubFactory  = Ember.Service.extend({
  data: null,
  init(){
    this.data = [];
  },
  pushPayload(payload){
      this.get('data').pushObject(payload); 
  },
  getAllPayloads(){
      return this.get('data');
  }
});

module('Unit | Instance Initializer | preload');

// This is your real test:
test('it works', function(assert) {
  let instance = storeStubFactory.create();

  initialize({lookup:function(serviceName){return serviceName==='service:store' ? instance : null;}}); 

  // confirm that mock service has the correct payload:   
  assert.ok(instance.getAllPayloads());
});

But I prefer to use first one. We stated that your instance-initializers behaviour as to put some data to the store which is provided by application. But in second option, it seems that we are also checking that your instance-initializer is calling the lookup function of appInstance too. This test is more coupled to your implementation detail.