tests: sync common testing infrastructure with ndn-cxx

Also upgrade waf to version 2.0.21

Change-Id: Ibfd3386772d48df287b6be73e6d778d3661abe86
diff --git a/tests/clock-fixture.hpp b/tests/clock-fixture.hpp
new file mode 100644
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--- /dev/null
+++ b/tests/clock-fixture.hpp
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+/* -*- Mode: C++; c-file-style: "gnu"; indent-tabs-mode:nil -*- */
+/*
+ * Copyright (c) 2013-2020  Regents of the University of California
+ *                          The University of Memphis
+ *
+ * This file is part of PSync.
+ *
+ * PSync 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.
+ *
+ * PSync 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 a copy of the GNU Lesser General Public License along with
+ * PSync, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef PSYNC_TESTS_CLOCK_FIXTURE_HPP
+#define PSYNC_TESTS_CLOCK_FIXTURE_HPP
+
+#include <ndn-cxx/util/time-unit-test-clock.hpp>
+
+namespace ndn {
+namespace tests {
+
+/** \brief A test fixture that overrides steady clock and system clock.
+ */
+class ClockFixture
+{
+public:
+  virtual
+  ~ClockFixture();
+
+  /** \brief Advance steady and system clocks.
+   *
+   *  Clocks are advanced in increments of \p tick for \p nTicks ticks.
+   *  afterTick() is called after each tick.
+   *
+   *  Exceptions thrown during I/O events are propagated to the caller.
+   *  Clock advancement will stop in the event of an exception.
+   */
+  void
+  advanceClocks(time::nanoseconds tick, size_t nTicks = 1)
+  {
+    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.
+   *  afterTick() is called after each tick.
+   *
+   *  Exceptions thrown during I/O events are propagated to the caller.
+   *  Clock advancement will stop in the event of an exception.
+   */
+  void
+  advanceClocks(time::nanoseconds tick, time::nanoseconds total);
+
+protected:
+  ClockFixture();
+
+private:
+  /** \brief Called by advanceClocks() after each clock advancement (tick).
+   *
+   *  The base class implementation is a no-op.
+   */
+  virtual void
+  afterTick()
+  {
+  }
+
+protected:
+  shared_ptr<time::UnitTestSteadyClock> m_steadyClock;
+  shared_ptr<time::UnitTestSystemClock> m_systemClock;
+};
+
+} // namespace tests
+} // namespace ndn
+
+#endif // PSYNC_TESTS_CLOCK_FIXTURE_HPP