diff --git a/tests/unit/clock-fixture.hpp b/tests/unit/clock-fixture.hpp
index 68dabbf..a0309ae 100644
--- a/tests/unit/clock-fixture.hpp
+++ b/tests/unit/clock-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).
  *
@@ -24,8 +24,7 @@
 
 #include "ndn-cxx/util/time-unit-test-clock.hpp"
 
-namespace ndn {
-namespace tests {
+namespace ndn::tests {
 
 /** \brief A test fixture that overrides steady clock and system clock.
  */
@@ -79,7 +78,6 @@
   shared_ptr<time::UnitTestSystemClock> m_systemClock;
 };
 
-} // namespace tests
-} // namespace ndn
+} // namespace ndn::tests
 
 #endif // NDN_CXX_TESTS_UNIT_CLOCK_FIXTURE_HPP