Add unit test asserting that serializable objects will never pass is_serialized(). see #17375.

git-svn-id: https://develop.svn.wordpress.org/trunk@32631 602fd350-edb4-49c9-b593-d223f7449a82

tests/phpunit/tests/functions.php

@@ -172,6 +172,13 @@ class Tests_Functions extends WP_UnitTestCase {
 			$this->assertFalse( is_serialized($case), "Test data: $case" );
 	}
 
+	/**
+	 * @ticket 17375
+	 */
+	function test_no_new_serializable_types() {
+		$this->assertFalse( is_serialized( 'C:16:"Serialized_Class":6:{a:0:{}}' ) );
+	}
+
 	/**
 	 * @group add_query_arg
 	 */