message: browser/ember: Rethrow errors in testing mode
  see
diff: @@ -49,6 +49,8 @@ export class Ember implements Integration {
  if (typeof oldOnError === 'function') {
  oldOnError.call(this.Ember, error);
  + } else if (this.Ember.testing) {
  + throw error;
  }
  };
  