Use es6-promise for an IE11 Promise polyfill.

This ensures that we support environments without a native `Promise` but
still avoid using the manually configured `Ember.RSVP` runloop
integration.

addon-test-support/@ember/test-helpers/-utils.ts

@@ -4,13 +4,9 @@ const HAS_PROMISE = typeof Promise === 'function';
 
 import RSVP from 'rsvp';
 import { run } from '@ember/runloop';
+import { Promise as PromisePolyfill } from 'es6-promise';
 
-const _Promise: typeof Promise = HAS_PROMISE
-  ? Promise
-  : (() => {
-      // FIXME: this needs to work on IE11
-      throw new Error('Missing global Promise!');
-    })();
+const _Promise: typeof Promise = HAS_PROMISE ? Promise : (PromisePolyfill as typeof Promise);
 
 export { _Promise as Promise };
 

ember-cli-build.js

@@ -30,8 +30,5 @@ module.exports = function (defaults) {
     type: 'test',
   });
 
-  app.import('vendor/shims/qunit.js', { type: 'test' });
-  app.import('vendor/promise-polyfill.js', { type: 'test' });
-
   return app.toTree();
 };

package.json

@@ -39,9 +39,11 @@
     "@ember/test-waiters": "^2.3.1",
     "broccoli-debug": "^0.6.5",
     "broccoli-funnel": "^3.0.3",
+    "ember-auto-import": "^1.7.0",
     "ember-cli-babel": "^7.22.1",
     "ember-cli-htmlbars": "^5.2.0",
-    "ember-destroyable-polyfill": "^2.0.2"
+    "ember-destroyable-polyfill": "^2.0.2",
+    "es6-promise": "^4.2.8"
   },
   "devDependencies": {
     "@ember/optional-features": "^1.3.0",

tests/test-helper.js

@@ -6,6 +6,12 @@ import { isSettled, getSettledState } from '@ember/test-helpers';
 import { run } from '@ember/runloop';
 import './helpers/resolver';
 
+import { polyfill } from 'es6-promise';
+
+if (typeof Promise === 'undefined') {
+  polyfill();
+}
+
 if (QUnit.config.seed) {
   QUnit.config.reorder = false;
 }