Specify types for mocks [MAILPOET-2488]

tests/integration/Services/BridgeTest.php

@@ -10,6 +10,7 @@ use MailPoet\Services\Bridge\BridgeTestMockAPI as MockAPI;
 use MailPoet\Settings\SettingsController;
 use MailPoet\Settings\SettingsRepository;
 use MailPoet\WP\Functions as WPFunctions;
+use PHPUnit_Framework_MockObject_MockObject as MockObject;
 
 require_once('BridgeTestMockAPI.php');
 
@@ -227,6 +228,7 @@ class BridgeTest extends \MailPoetTest {
 
   public function testItChecksAndStoresKeysOnSettingsSave() {
     $response = ['abc' => 'def'];
+    /** @var MockObject $bridge */
     $bridge = Stub::makeEmptyExcept(
       $this->bridge,
       'onSettingsSave',