Added test to demonstrate backwards compatibility

Added a test to demonstrate that the plugin manager returned is both an
instance of the zend-hydrator plugin manager as well as the zend-stdlib
HydratorPluginManager.

Author: weierophinney

src/Service/HydratorManagerFactory.php

@@ -11,5 +11,8 @@
 
 class HydratorManagerFactory extends AbstractPluginManagerFactory
 {
+    /**
+     * @todo Switch to Zend\Hydrator\HydratorPluginManager for 3.0 (if kept)
+     */
     const PLUGIN_MANAGER_CLASS = 'Zend\Stdlib\Hydrator\HydratorPluginManager';
 }

test/Service/HydratorManagerFactoryTest.php

@@ -0,0 +1,42 @@
+<?php
+/**
+ * Zend Framework (http://framework.zend.com/)
+ *
+ * @link      http://github.com/zendframework/zf2 for the canonical source repository
+ * @copyright Copyright (c) 2005-2015 Zend Technologies USA Inc. (http://www.zend.com)
+ * @license   http://framework.zend.com/license/new-bsd New BSD License
+ */
+
+namespace ZendTest\Mvc\Service;
+
+use PHPUnit_Framework_TestCase as TestCase;
+use Zend\Hydrator\HydratorPluginManager as ZendHydratorManager;
+use Zend\Mvc\Service\HydratorManagerFactory;
+use Zend\ServiceManager\ServiceLocatorInterface;
+use Zend\Stdlib\Hydrator\HydratorPluginManager;
+
+class HydratorManagerFactoryTest extends TestCase
+{
+    public function setUp()
+    {
+        $this->factory = new HydratorManagerFactory();
+        $this->services = $this->prophesize(ServiceLocatorInterface::class);
+        $this->services->get('Config')->willReturn([]);
+    }
+
+    public function testFactoryReturnsZendHydratorManagerInstance()
+    {
+        $hydrators = $this->factory->createService($this->services->reveal());
+        $this->assertInstanceOf(ZendHydratorManager::class, $hydrators);
+        return $hydrators;
+    }
+
+    /**
+     * @todo Remove for 3.0
+     * @depends testFactoryReturnsZendHydratorManagerInstance
+     */
+    public function testFactoryReturnsStdlibHydratorManagerInstance($hydrators)
+    {
+        $this->assertInstanceOf(HydratorPluginManager::class, $hydrators);
+    }
+}