diff --git a/tests/test-common.hpp b/tests/test-common.hpp
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+++ b/tests/test-common.hpp
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+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2014-2015,  Regents of the University of California,
+ *                           Arizona Board of Regents,
+ *                           Colorado State University,
+ *                           University Pierre & Marie Curie, Sorbonne University,
+ *                           Washington University in St. Louis,
+ *                           Beijing Institute of Technology,
+ *                           The University of Memphis.
+ *
+ * This file is part of ndn-tools (Named Data Networking Essential Tools).
+ * See AUTHORS.md for complete list of ndn-tools authors and contributors.
+ *
+ * ndn-tools is free software: you can redistribute it and/or modify it under the terms
+ * of the GNU General Public License as published by the Free Software Foundation,
+ * either version 3 of the License, or (at your option) any later version.
+ *
+ * ndn-tools 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * ndn-tools, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef NDN_TOOLS_TESTS_TEST_COMMON_HPP
+#define NDN_TOOLS_TESTS_TEST_COMMON_HPP
+
+#include "boost-test.hpp"
+
+#include <ndn-cxx/util/time-unit-test-clock.hpp>
+#include <ndn-cxx/name.hpp>
+#include <ndn-cxx/interest.hpp>
+#include <ndn-cxx/data.hpp>
+#include <ndn-cxx/signature.hpp>
+#include <ndn-cxx/security/signature-sha256-with-rsa.hpp>
+
+#include <boost/asio/io_service.hpp>
+
+namespace ndn {
+namespace tests {
+
+/** \brief a test fixture that overrides steady clock and system clock
+ */
+class UnitTestTimeFixture
+{
+protected:
+  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, the supplied 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(boost::asio::io_service& io,
+                const time::nanoseconds& tick, size_t nTicks = 1)
+  {
+    BOOST_ASSERT(nTicks >= 0);
+
+    this->advanceClocks(io, 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, the supplied 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(boost::asio::io_service& io,
+                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();
+    }
+  }
+
+protected:
+  shared_ptr<time::UnitTestSteadyClock> steadyClock;
+  shared_ptr<time::UnitTestSystemClock> systemClock;
+};
+
+inline shared_ptr<Interest>
+makeInterest(const Name& name)
+{
+  return make_shared<Interest>(name);
+}
+
+inline shared_ptr<Data>
+signData(const shared_ptr<Data>& data)
+{
+  ndn::SignatureSha256WithRsa fakeSignature;
+  fakeSignature.setValue(ndn::dataBlock(tlv::SignatureValue,
+                                        static_cast<const uint8_t*>(nullptr), 0));
+  data->setSignature(fakeSignature);
+  data->wireEncode();
+
+  return data;
+}
+
+inline shared_ptr<Data>
+makeData(const Name& name)
+{
+  shared_ptr<Data> data = make_shared<Data>(name);
+  return signData(data);
+}
+
+
+} // namespace tests
+} // namespace ndn
+
+#endif // NDN_TOOLS_TESTS_TEST_COMMON_HPP