diff --git a/tests/unit/io-fixture.hpp b/tests/unit/io-fixture.hpp
index 1c872c4..4934954 100644
--- a/tests/unit/io-fixture.hpp
+++ b/tests/unit/io-fixture.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2020 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -26,8 +26,7 @@
 
 #include <boost/asio/io_service.hpp>
 
-namespace ndn {
-namespace tests {
+namespace ndn::tests {
 
 class IoFixture : public ClockFixture
 {
@@ -49,7 +48,6 @@
   boost::asio::io_service m_io;
 };
 
-} // namespace tests
-} // namespace ndn
+} // namespace ndn::tests
 
 #endif // NDN_CXX_TESTS_UNIT_IO_FIXTURE_HPP