Update ApiClientTest.php

Add test that the IO class on App Engine is always Google_Io_Stream.

Author: sjlangley

tests/general/ApiClientTest.php

@@ -131,6 +131,7 @@ public function testAppEngineAutoConfig()
     $_SERVER['SERVER_SOFTWARE'] = 'Google App Engine';
     $client = new Google_Client();
     $this->assertInstanceOf('Google_Cache_Memcache', $client->getCache());
+    $this->assertInstanceOf('Google_Io_Stream', $client->getIo());
     unset($_SERVER['SERVER_SOFTWARE']);
   }