Failing test

tests/dummy/app/mixins/itemizable.js

@@ -0,0 +1,3 @@
+import Mixin from '@ember/object/mixin';
+
+export default Mixin.create({});

tests/dummy/app/models/homepage-item.js

@@ -0,0 +1,7 @@
+import DS from 'ember-data';
+
+export default DS.Model.extend({
+
+  itemizable: DS.belongsTo({ polymorphic: true }),
+
+});

tests/integration/mixins/loadable-store/load-records-test.js

@@ -2,32 +2,14 @@ import { module, test } from 'qunit';
 import { setupTest } from 'ember-qunit';
 import { waitUntil } from '@ember/test-helpers';
 import MirageServer from 'dummy/tests/integration/helpers/mirage-server';
-import { Model, hasMany, belongsTo } from 'ember-cli-mirage';
 import LoadableStore from 'ember-data-storefront/mixins/loadable-store';
 
 module('Integration | Mixins | LoadableStore | loadRecords', function(hooks) {
   setupTest(hooks);
 
   hooks.beforeEach(function() {
     this.server = new MirageServer({
-      models: {
-        post: Model.extend({
-          comments: hasMany(),
-          author: belongsTo(),
-          tags: hasMany()
-        }),
-        comment: Model.extend({
-          post: belongsTo(),
-          author: belongsTo()
-        }),
-        tag: Model.extend({
-          posts: hasMany()
-        }),
-        author: Model.extend({
-          comments: hasMany(),
-          posts: hasMany()
-        })
-      },
+      discoverEmberDataModels: true,
       baseConfig() {
         this.resource('posts');
       }
@@ -146,6 +128,20 @@ module('Integration | Mixins | LoadableStore | loadRecords', function(hooks) {
     assert.equal(posts.get('firstObject.comments.length'), 2);
   });
 
+  test('it can load a polymorphic collection with model-specific includes', async function(assert) {
+    server.logging = true;
+    this.server.get('/homepage-items');
+    let post = this.server.create('post');
+    let comment = this.server.create('comment');
+    this.server.create('homepage-item', { itemizable: post });
+    this.server.create('homepage-item', { itemizable: comment });
+
+    await this.store.loadRecords('homepage-item', { include: 'itemizable.tags' });
+
+    assert.ok(this.store.peekRecord('post', post.id));
+    assert.ok(this.store.peekRecord('comment', comment.id));
+  });
+
   module('Tracking includes', function() {
     test('it will track an include', async function(assert) {
       let serverPost = this.server.create('post', { title: 'My post' });