[BUGFIX] account for observer changes in ember 3.13+

packages/-ember-data/tests/unit/model/rollback-attributes-test.js

@@ -12,6 +12,7 @@ import { module, test } from 'qunit';
 import DS from 'ember-data';
 import { setupTest } from 'ember-qunit';
 import { settled } from '@ember/test-helpers';
+import { gte } from 'ember-compatibility-helpers';
 
 let env, store, Person;
 
@@ -367,7 +368,11 @@ module('unit/model/rollbackAttributes - model.rollbackAttributes()', function(ho
   });
 
   test("invalid record's attributes can be rollbacked", async function(assert) {
-    assert.expect(12);
+    if (gte('3.13.0')) {
+      assert.expect(14);
+    } else {
+      assert.expect(13);
+    }
 
     class Dog extends Model {
       @attr() name;
@@ -438,7 +443,11 @@ module('unit/model/rollbackAttributes - model.rollbackAttributes()', function(ho
   });
 
   test(`invalid record's attributes rolled back to correct state after set`, async function(assert) {
-    assert.expect(14);
+    if (gte('3.13.0')) {
+      assert.expect(15);
+    } else {
+      assert.expect(14);
+    }
 
     class Dog extends Model {
       @attr() name;