fix code to match '2.1' requirements

tests/framework/db/ActiveRecordTest.php

@@ -1729,6 +1729,6 @@ abstract class ActiveRecordTest extends DatabaseTestCase
     public function testCustomARRelation()
     {
         $orderItem = OrderItem::findOne(1);
-        $this->assertInstanceOf(Order::className(), $orderItem->custom);
+        $this->assertInstanceOf(Order::class, $orderItem->custom);
     }
 }

tests/framework/filters/auth/CompositeAuthTest.php

@@ -129,7 +129,7 @@ class CompositeAuthTest extends \yiiunit\TestCase
 
     public function testCompositeAuth()
     {
-        Yii::$app->request->headers->set('Authorization', base64_encode("foo:bar"));
+        Yii::$app->request->setHeader('Authorization', base64_encode("foo:bar"));
         /** @var TestAuthController $controller */
         $controller = Yii::$app->createController('test')[0];
         $controller->authMethods = [