diff --git a/tests/unit/security/validator-fixture.cpp b/tests/unit/security/validator-fixture.cpp
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+++ b/tests/unit/security/validator-fixture.cpp
@@ -0,0 +1,103 @@
+/* -*- 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.
+ */
+
+#include "tests/unit/security/validator-fixture.hpp"
+
+#include "ndn-cxx/security/additional-description.hpp"
+
+namespace ndn {
+namespace security {
+inline namespace v2 {
+namespace tests {
+
+const time::milliseconds ValidatorFixtureBase::s_mockPeriod{250};
+const int ValidatorFixtureBase::s_mockTimes = 200;
+
+ValidatorFixtureBase::ValidatorFixtureBase()
+{
+  processInterest = [this] (const Interest& interest) {
+    auto cert = cache.find(interest);
+    if (cert != nullptr) {
+      face.receive(*cert);
+    }
+  };
+}
+
+void
+ValidatorFixtureBase::mockNetworkOperations()
+{
+  util::signal::ScopedConnection conn = face.onSendInterest.connect([this] (const Interest& interest) {
+    if (processInterest) {
+      m_io.post(bind(processInterest, interest));
+    }
+  });
+  advanceClocks(s_mockPeriod, s_mockTimes);
+}
+
+Identity
+ValidatorFixtureBase::addSubCertificate(const Name& subIdentityName, const Identity& issuer)
+{
+  auto subId = m_keyChain.createIdentity(subIdentityName);
+  auto cert = subId.getDefaultKey().getDefaultCertificate();
+  cert.setName(cert.getKeyName()
+               .append("parent")
+               .appendVersion());
+
+  SignatureInfo info;
+  auto now = time::system_clock::now();
+  info.setValidityPeriod(ValidityPeriod(now, now + 90_days));
+
+  AdditionalDescription description;
+  description.set("type", "sub-certificate");
+  info.addCustomTlv(description.wireEncode());
+
+  m_keyChain.sign(cert, signingByIdentity(issuer).setSignatureInfo(info));
+  m_keyChain.setDefaultCertificate(subId.getDefaultKey(), cert);
+
+  return subId;
+}
+
+Name
+InterestV02Pkt::makeName(Name name, KeyChain& keyChain)
+{
+  Interest interest(name);
+  interest.setCanBePrefix(false);
+  SigningInfo params;
+  params.setSignedInterestFormat(SignedInterestFormat::V02);
+  keyChain.sign(interest, params);
+  return interest.getName();
+}
+
+Name
+InterestV03Pkt::makeName(Name name, KeyChain& keyChain)
+{
+  Interest interest(name);
+  interest.setCanBePrefix(false);
+  SigningInfo params;
+  params.setSignedInterestFormat(SignedInterestFormat::V03);
+  keyChain.sign(interest, params);
+  return interest.getName();
+}
+
+} // namespace tests
+} // inline namespace v2
+} // namespace security
+} // namespace ndn