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) 2013-2020 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_CXX_TESTS_TEST_COMMON_HPP
+#define NDN_CXX_TESTS_TEST_COMMON_HPP
+
+#include "ndn-cxx/data.hpp"
+#include "ndn-cxx/interest.hpp"
+#include "ndn-cxx/lp/nack.hpp"
+#include "tests/boost-test.hpp"
+
+namespace ndn {
+namespace tests {
+
+/**
+ * \brief Create an Interest
+ */
+shared_ptr<Interest>
+makeInterest(const Name& name, bool canBePrefix = false,
+             optional<time::milliseconds> lifetime = nullopt,
+             optional<Interest::Nonce> nonce = nullopt);
+
+/**
+ * \brief Create a Data with a null (i.e., empty) signature
+ *
+ * If a "real" signature is desired, use KeyChainFixture and sign again with `m_keyChain`.
+ */
+shared_ptr<Data>
+makeData(const Name& name);
+
+/**
+ * \brief Add a null signature to \p data
+ */
+Data&
+signData(Data& data);
+
+/**
+ * \brief Add a null signature to \p data
+ */
+inline shared_ptr<Data>
+signData(shared_ptr<Data> data)
+{
+  signData(*data);
+  return data;
+}
+
+/**
+ * \brief Create a Nack
+ */
+lp::Nack
+makeNack(Interest interest, lp::NackReason reason);
+
+/**
+ * \brief Replace a name component in a packet
+ * \param[inout] pkt the packet
+ * \param index the index of the name component to replace
+ * \param args arguments to name::Component constructor
+ */
+template<typename Packet, typename ...Args>
+void
+setNameComponent(Packet& pkt, ssize_t index, Args&& ...args)
+{
+  Name name = pkt.getName();
+  name.set(index, name::Component(std::forward<Args>(args)...));
+  pkt.setName(name);
+}
+
+} // namespace tests
+} // namespace ndn
+
+#endif // NDN_CXX_TESTS_TEST_COMMON_HPP