[tests] Use @requires annotation when possible

Author: nicolas-grekas

Tests/ParserTest.php

@@ -446,14 +446,11 @@ public function testObjectsSupportDisabledWithExceptions()
         $this->parser->parse('foo: !!php/object:O:30:"Symfony\Tests\Component\Yaml\B":1:{s:1:"b";s:3:"foo";}', true, false);
     }
 
+    /**
+     * @requires extension iconv
+     */
     public function testNonUtf8Exception()
     {
-        if (!function_exists('iconv')) {
-            $this->markTestSkipped('Exceptions for non-utf8 charsets require the iconv() function.');
-
-            return;
-        }
-
         $yamls = array(
             iconv('UTF-8', 'ISO-8859-1', "foo: 'äöüß'"),
             iconv('UTF-8', 'ISO-8859-15', "euro: '€'"),