diff --git a/tests/unit-test-common-fixtures.cpp b/tests/unit-test-common-fixtures.cpp
new file mode 100644
index 0000000..f001ef7
--- /dev/null
+++ b/tests/unit-test-common-fixtures.cpp
@@ -0,0 +1,75 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2014-2018, Regents of the University of California
+ *
+ * NAC 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.
+ *
+ * NAC 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 NAC library authors and contributors.
+ */
+
+#include "tests-common.hpp"
+
+namespace ndn {
+namespace nac {
+namespace tests {
+
+BaseFixture::BaseFixture()
+{
+}
+
+UnitTestTimeFixture::UnitTestTimeFixture()
+  : steadyClock(make_shared<time::UnitTestSteadyClock>())
+  , systemClock(make_shared<time::UnitTestSystemClock>())
+{
+  time::setCustomClocks(steadyClock, systemClock);
+}
+
+UnitTestTimeFixture::~UnitTestTimeFixture()
+{
+  time::setCustomClocks(nullptr, nullptr);
+}
+
+void
+UnitTestTimeFixture::advanceClocks(const time::nanoseconds& tick, size_t nTicks)
+{
+  this->advanceClocks(tick, tick * nTicks);
+}
+
+void
+UnitTestTimeFixture::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 (m_io.stopped())
+      m_io.reset();
+    m_io.poll();
+  }
+}
+
+} // namespace tests
+} // namespace nac
+} // namespace ndn