tests: avoid deprecated boost headers
Change-Id: I05aa8d5fd22843415db09478f7b53f1810b38db3
diff --git a/tests/unit/util/string-helper.t.cpp b/tests/unit/util/string-helper.t.cpp
index ae89ba7..8747301 100644
--- a/tests/unit/util/string-helper.t.cpp
+++ b/tests/unit/util/string-helper.t.cpp
@@ -1,6 +1,6 @@
/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
- * Copyright (c) 2013-2018 Regents of the University of California.
+ * Copyright (c) 2013-2019 Regents of the University of California.
*
* This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
*
@@ -26,7 +26,12 @@
#include <cctype>
#include <cstring>
+
+#if BOOST_VERSION >= 105900
+#include <boost/test/tools/output_test_stream.hpp>
+#else
#include <boost/test/output_test_stream.hpp>
+#endif
namespace ndn {
namespace util {