phpunit compatibility

tst/Data/GoogleCloudStorageTest.php

@@ -10,7 +10,7 @@ class GoogleCloudStorageTest extends TestCase
     private static $_client;
     private static $_bucket;
 
-    public static function setUpBeforeClass()
+    public static function setUpBeforeClass(): void
     {
         $httpClient = new Client(array('debug'=>false));
         $handler    = HttpHandlerFactory::build($httpClient);
@@ -24,7 +24,7 @@ class GoogleCloudStorageTest extends TestCase
         self::$_bucket = self::$_client->createBucket($name);
     }
 
-    public function setUp()
+    public function setUp(): void
     {
         ini_set('error_log', stream_get_meta_data(tmpfile())['uri']);
         $this->_model = GoogleCloudStorage::getInstance(array(
@@ -33,7 +33,7 @@ class GoogleCloudStorageTest extends TestCase
         ));
     }
 
-    public function tearDown()
+    public function tearDown(): void
     {
         foreach (self::$_bucket->objects() as $object) {
             $object->delete();