diff --git a/tests/unit-test-time-fixture.hpp b/tests/unit-test-time-fixture.hpp
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+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/*
+ * Copyright (c) 2013-2019 Regents of the University of California.
+ *
+ * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
+ *
+ * ndn-cxx library is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU Lesser General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later version.
+ *
+ * ndn-cxx library is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+ * PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more details.
+ *
+ * You should have received copies of the GNU General Public License and GNU Lesser
+ * General Public License along with ndn-cxx, e.g., in COPYING.md file.  If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ * See AUTHORS.md for complete list of ndn-cxx authors and contributors.
+ */
+
+#ifndef NDN_TESTS_UNIT_UNIT_TEST_TIME_FIXTURE_HPP
+#define NDN_TESTS_UNIT_UNIT_TEST_TIME_FIXTURE_HPP
+
+#include <ndn-cxx/util/time-unit-test-clock.hpp>
+#include <boost/asio/io_service.hpp>
+
+namespace ndn {
+namespace ndncert {
+namespace tests {
+
+/** \brief a test fixture that overrides steady clock and system clock
+ */
+class UnitTestTimeFixture
+{
+public:
+  UnitTestTimeFixture()
+    : steadyClock(make_shared<time::UnitTestSteadyClock>())
+    , systemClock(make_shared<time::UnitTestSystemClock>())
+  {
+    time::setCustomClocks(steadyClock, systemClock);
+  }
+
+  ~UnitTestTimeFixture()
+  {
+    time::setCustomClocks(nullptr, nullptr);
+  }
+
+  /** \brief advance steady and system clocks
+   *
+   *  Clocks are advanced in increments of \p tick for \p nTicks ticks.
+   *  After each tick, io_service is polled to process pending I/O events.
+   *
+   *  Exceptions thrown during I/O events are propagated to the caller.
+   *  Clock advancing would stop in case of an exception.
+   */
+  void
+  advanceClocks(const time::nanoseconds& tick, size_t nTicks = 1)
+  {
+    this->advanceClocks(tick, tick * nTicks);
+  }
+
+  /** \brief advance steady and system clocks
+   *
+   *  Clocks are advanced in increments of \p tick for \p total time.
+   *  The last increment might be shorter than \p tick.
+   *  After each tick, io_service is polled to process pending I/O events.
+   *
+   *  Exceptions thrown during I/O events are propagated to the caller.
+   *  Clock advancing would stop in case of an exception.
+   */
+  void
+  advanceClocks(const time::nanoseconds& tick, const time::nanoseconds& total)
+  {
+    BOOST_ASSERT(tick > time::nanoseconds::zero());
+    BOOST_ASSERT(total >= time::nanoseconds::zero());
+
+    time::nanoseconds remaining = total;
+    while (remaining > time::nanoseconds::zero()) {
+      if (remaining >= tick) {
+        steadyClock->advance(tick);
+        systemClock->advance(tick);
+        remaining -= tick;
+      }
+      else {
+        steadyClock->advance(remaining);
+        systemClock->advance(remaining);
+        remaining = time::nanoseconds::zero();
+      }
+
+      if (io.stopped())
+        io.reset();
+      io.poll();
+    }
+  }
+
+public:
+  shared_ptr<time::UnitTestSteadyClock> steadyClock;
+  shared_ptr<time::UnitTestSystemClock> systemClock;
+  boost::asio::io_service io;
+};
+
+} // namespace tests
+} // namespace ndncert
+} // namespace ndn
+
+#endif // NDN_TESTS_UNIT_UNIT_TEST_TIME_FIXTURE_HPP