added missing methods

Author: Matias Melograno

tests/Suite/Sdk/SdkClientTest.php

@@ -487,8 +487,7 @@ public function testCacheExceptionReturnsControl()
         $splitSdk = $splitFactory->client();
 
         $cachePoolMethods = array(
-            'getItem', 'getItems', 'getItemOnList', 'getItemsOnList', 'isItemOnList',
-            'getKeys', 'rightPushInList'
+            'getItem', 'getItems', 'isItemOnList', 'getKeys', 'rightPushInList', 'expireKey'
         );
         $cachePool = $this
             ->getMockBuilder('\SplitIO\Component\Cache\Pool')