diff --git a/tests/unit/security/additional-description.t.cpp b/tests/unit/security/additional-description.t.cpp
index 82dd606..af71ce4 100644
--- a/tests/unit/security/additional-description.t.cpp
+++ b/tests/unit/security/additional-description.t.cpp
@@ -24,9 +24,9 @@
 
 #include "tests/boost-test.hpp"
 
-namespace ndn {
-namespace security {
-namespace tests {
+namespace ndn::tests {
+
+using ndn::security::AdditionalDescription;
 
 BOOST_CONCEPT_ASSERT((boost::EqualityComparable<AdditionalDescription>));
 BOOST_CONCEPT_ASSERT((WireEncodable<AdditionalDescription>));
@@ -99,6 +99,4 @@
 BOOST_AUTO_TEST_SUITE_END() // TestAdditionalDescription
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/certificate-bundle-fetcher.t.cpp b/tests/unit/security/certificate-bundle-fetcher.t.cpp
index 0c300b7..1c7b8b8 100644
--- a/tests/unit/security/certificate-bundle-fetcher.t.cpp
+++ b/tests/unit/security/certificate-bundle-fetcher.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2020 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -26,12 +26,9 @@
 #include "tests/test-common.hpp"
 #include "tests/unit/security/validator-fixture.hpp"
 
-namespace ndn {
-namespace security {
-inline namespace v2 {
-namespace tests {
+namespace ndn::tests {
 
-using namespace ndn::tests;
+using namespace ndn::security;
 
 BOOST_AUTO_TEST_SUITE(Security)
 BOOST_AUTO_TEST_SUITE(TestCertificateBundleFetcher)
@@ -45,21 +42,10 @@
   }
 };
 
-class BundleWithFinalBlockId
-{
-};
-
-class BundleWithoutFinalBlockId
-{
-};
-
-class Timeout
-{
-};
-
-class Nack
-{
-};
+struct BundleWithFinalBlockId {};
+struct BundleWithoutFinalBlockId {};
+struct Timeout {};
+struct Nack {};
 
 template<class Response>
 class CertificateBundleFetcherFixture : public HierarchicalValidatorFixture<ValidationPolicySimpleHierarchy,
@@ -198,7 +184,4 @@
 BOOST_AUTO_TEST_SUITE_END() // TestCertificateBundleFetcher
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // inline namespace v2
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/certificate-cache.t.cpp b/tests/unit/security/certificate-cache.t.cpp
index 51aa72b..acbdd00 100644
--- a/tests/unit/security/certificate-cache.t.cpp
+++ b/tests/unit/security/certificate-cache.t.cpp
@@ -25,12 +25,7 @@
 #include "tests/key-chain-fixture.hpp"
 #include "tests/unit/clock-fixture.hpp"
 
-namespace ndn {
-namespace security {
-inline namespace v2 {
-namespace tests {
-
-using namespace ndn::tests;
+namespace ndn::tests {
 
 class CertificateCacheFixture : public ClockFixture, public KeyChainFixture
 {
@@ -60,7 +55,7 @@
   }
 
 public:
-  CertificateCache certCache;
+  security::CertificateCache certCache;
   Identity identity;
   Certificate cert;
 };
@@ -104,7 +99,4 @@
 BOOST_AUTO_TEST_SUITE_END() // TestCertificateCache
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // inline namespace v2
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/certificate-fetcher-direct-fetch.t.cpp b/tests/unit/security/certificate-fetcher-direct-fetch.t.cpp
index 7c9ba90..a843ca6 100644
--- a/tests/unit/security/certificate-fetcher-direct-fetch.t.cpp
+++ b/tests/unit/security/certificate-fetcher-direct-fetch.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2022 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -30,27 +30,16 @@
 #include <boost/range/adaptor/sliced.hpp>
 #include <boost/range/adaptor/strided.hpp>
 
-namespace ndn {
-namespace security {
-inline namespace v2 {
-namespace tests {
+namespace ndn::tests {
 
-using namespace ndn::tests;
+using namespace ndn::security;
 
 BOOST_AUTO_TEST_SUITE(Security)
 BOOST_AUTO_TEST_SUITE(TestCertificateFetcherDirectFetch)
 
-class Cert
-{
-};
-
-class Timeout
-{
-};
-
-class Nack
-{
-};
+struct Cert {};
+struct Timeout {};
+struct Nack {};
 
 template<class Response>
 class CertificateFetcherDirectFetchFixture : public HierarchicalValidatorFixture<ValidationPolicySimpleHierarchy,
@@ -260,7 +249,4 @@
 BOOST_AUTO_TEST_SUITE_END() // TestCertificateFetcherDirectFetch
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // inline namespace v2
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/certificate-fetcher-from-network.t.cpp b/tests/unit/security/certificate-fetcher-from-network.t.cpp
index cb3e0b5..7ffc276 100644
--- a/tests/unit/security/certificate-fetcher-from-network.t.cpp
+++ b/tests/unit/security/certificate-fetcher-from-network.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2022 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -27,27 +27,16 @@
 #include "tests/boost-test.hpp"
 #include "tests/unit/security/validator-fixture.hpp"
 
-namespace ndn {
-namespace security {
-inline namespace v2 {
-namespace tests {
+namespace ndn::tests {
 
-using namespace ndn::tests;
+using namespace ndn::security;
 
 BOOST_AUTO_TEST_SUITE(Security)
 BOOST_AUTO_TEST_SUITE(TestCertificateFetcherFromNetwork)
 
-class Cert
-{
-};
-
-class Timeout
-{
-};
-
-class Nack
-{
-};
+struct Cert {};
+struct Timeout {};
+struct Nack {};
 
 template<class Response>
 class CertificateFetcherFromNetworkFixture : public HierarchicalValidatorFixture<ValidationPolicySimpleHierarchy,
@@ -135,7 +124,4 @@
 BOOST_AUTO_TEST_SUITE_END() // TestCertificateFetcherFromNetwork
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // inline namespace v2
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/certificate-fetcher-offline.t.cpp b/tests/unit/security/certificate-fetcher-offline.t.cpp
index f48971f..147701f 100644
--- a/tests/unit/security/certificate-fetcher-offline.t.cpp
+++ b/tests/unit/security/certificate-fetcher-offline.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2022 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -25,10 +25,9 @@
 #include "tests/boost-test.hpp"
 #include "tests/unit/security/validator-fixture.hpp"
 
-namespace ndn {
-namespace security {
-inline namespace v2 {
-namespace tests {
+namespace ndn::tests {
+
+using namespace ndn::security;
 
 BOOST_AUTO_TEST_SUITE(Security)
 
@@ -66,7 +65,4 @@
 BOOST_AUTO_TEST_SUITE_END() // TestCertificateFetcherOffline
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // inline namespace v2
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/certificate.t.cpp b/tests/unit/security/certificate.t.cpp
index 44ae731..facb261 100644
--- a/tests/unit/security/certificate.t.cpp
+++ b/tests/unit/security/certificate.t.cpp
@@ -30,12 +30,10 @@
 
 #include <boost/lexical_cast.hpp>
 
-namespace ndn {
-namespace security {
-inline namespace v2 {
-namespace tests {
+namespace ndn::tests {
 
-using namespace ndn::tests;
+using ndn::security::Certificate;
+using ndn::security::ValidityPeriod;
 
 BOOST_CONCEPT_ASSERT((WireEncodable<Certificate>));
 BOOST_CONCEPT_ASSERT((WireDecodable<Certificate>));
@@ -379,6 +377,9 @@
 
 BOOST_AUTO_TEST_CASE(Helpers)
 {
+  using ndn::security::extractIdentityFromCertName;
+  using ndn::security::extractKeyNameFromCertName;
+
   BOOST_CHECK_EQUAL(extractIdentityFromCertName("/KEY/hello/world/v=1"), "/");
   BOOST_CHECK_EQUAL(extractIdentityFromCertName("/hello/world/KEY/!/self/v=42"), "/hello/world");
 
@@ -399,7 +400,4 @@
 BOOST_AUTO_TEST_SUITE_END() // TestCertificate
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // inline namespace v2
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/detail/certificate-bundle-decoder.t.cpp b/tests/unit/security/detail/certificate-bundle-decoder.t.cpp
index a9fe998..3cb3eb7 100644
--- a/tests/unit/security/detail/certificate-bundle-decoder.t.cpp
+++ b/tests/unit/security/detail/certificate-bundle-decoder.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2022 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -24,12 +24,9 @@
 #include "tests/boost-test.hpp"
 #include "tests/key-chain-fixture.hpp"
 
-namespace ndn {
-namespace security {
-namespace detail {
-namespace tests {
+namespace ndn::tests {
 
-class CertificateBundleDecoderFixture : public ndn::tests::KeyChainFixture
+class CertificateBundleDecoderFixture : public KeyChainFixture
 {
 protected:
   CertificateBundleDecoderFixture()
@@ -51,7 +48,7 @@
   }
 
 protected:
-  CertificateBundleDecoder cbd;
+  security::detail::CertificateBundleDecoder cbd;
   Block certBlock1;
   Block certBlock2;
   size_t nCertsCompleted = 0;
@@ -213,7 +210,4 @@
 BOOST_AUTO_TEST_SUITE_END() // TestCertificateBundleEncoderDecoder
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace detail
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/interest-signer.t.cpp b/tests/unit/security/interest-signer.t.cpp
index b4a3991..b44546b 100644
--- a/tests/unit/security/interest-signer.t.cpp
+++ b/tests/unit/security/interest-signer.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2022 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -25,11 +25,10 @@
 #include "tests/key-chain-fixture.hpp"
 #include "tests/unit/clock-fixture.hpp"
 
-namespace ndn {
-namespace security {
-namespace tests {
+namespace ndn::tests {
 
-using namespace ndn::tests;
+using ndn::security::InterestSigner;
+using ndn::security::SigningInfo;
 
 class InterestSignerFixture : public ClockFixture, public KeyChainFixture
 {
@@ -123,6 +122,4 @@
 BOOST_AUTO_TEST_SUITE_END() // TestInterestSigner
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/key-chain.t.cpp b/tests/unit/security/key-chain.t.cpp
index be544a4..d0b717f 100644
--- a/tests/unit/security/key-chain.t.cpp
+++ b/tests/unit/security/key-chain.t.cpp
@@ -31,12 +31,9 @@
 #include <openssl/opensslv.h>
 #include <boost/mpl/vector.hpp>
 
-namespace ndn {
-namespace security {
-inline namespace v2 {
-namespace tests {
+namespace ndn::tests {
 
-using namespace ndn::tests;
+using namespace ndn::security;
 
 BOOST_AUTO_TEST_SUITE(Security)
 BOOST_FIXTURE_TEST_SUITE(TestKeyChain, TestHomeEnvSaver)
@@ -800,7 +797,4 @@
 BOOST_AUTO_TEST_SUITE_END() // TestKeyChain
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // inline namespace v2
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/key-params.t.cpp b/tests/unit/security/key-params.t.cpp
index f051b06..27f098a 100644
--- a/tests/unit/security/key-params.t.cpp
+++ b/tests/unit/security/key-params.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2022 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -25,8 +25,7 @@
 
 #include <boost/lexical_cast.hpp>
 
-namespace ndn {
-namespace tests {
+namespace ndn::tests {
 
 BOOST_AUTO_TEST_SUITE(Security)
 BOOST_AUTO_TEST_SUITE(TestKeyParams)
@@ -162,5 +161,4 @@
 BOOST_AUTO_TEST_SUITE_END() // TestKeyParams
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/pib/certificate-container.t.cpp b/tests/unit/security/pib/certificate-container.t.cpp
index b1d4343..ecfd0b9 100644
--- a/tests/unit/security/pib/certificate-container.t.cpp
+++ b/tests/unit/security/pib/certificate-container.t.cpp
@@ -26,15 +26,13 @@
 #include "tests/boost-test.hpp"
 #include "tests/unit/security/pib/pib-data-fixture.hpp"
 
-namespace ndn {
-namespace security {
-namespace pib {
-namespace tests {
+namespace ndn::tests {
+
+using namespace ndn::security::pib;
 
 NDN_CXX_ASSERT_FORWARD_ITERATOR(CertificateContainer::const_iterator);
 
 BOOST_AUTO_TEST_SUITE(Security)
-BOOST_AUTO_TEST_SUITE(Pib)
 BOOST_FIXTURE_TEST_SUITE(TestCertificateContainer, PibDataFixture)
 
 BOOST_AUTO_TEST_CASE(AddGetRemove)
@@ -72,7 +70,7 @@
     BOOST_CHECK_EQUAL(cert1, id1Key1Cert1);
     BOOST_CHECK_EQUAL(cert2, id1Key1Cert2);
     Name id1Key1Cert3Name = Name(id1Key1Name).append("issuer").appendVersion(3);
-    BOOST_CHECK_THROW(container.get(id1Key1Cert3Name), pib::Pib::Error);
+    BOOST_CHECK_THROW(container.get(id1Key1Cert3Name), Pib::Error);
   }
 
   {
@@ -158,10 +156,6 @@
 }
 
 BOOST_AUTO_TEST_SUITE_END() // TestCertificateContainer
-BOOST_AUTO_TEST_SUITE_END() // Pib
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace pib
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/pib/identity-container.t.cpp b/tests/unit/security/pib/identity-container.t.cpp
index ea97da0..81f9ad0 100644
--- a/tests/unit/security/pib/identity-container.t.cpp
+++ b/tests/unit/security/pib/identity-container.t.cpp
@@ -26,15 +26,13 @@
 #include "tests/boost-test.hpp"
 #include "tests/unit/security/pib/pib-data-fixture.hpp"
 
-namespace ndn {
-namespace security {
-namespace pib {
-namespace tests {
+namespace ndn::tests {
+
+using namespace ndn::security::pib;
 
 NDN_CXX_ASSERT_FORWARD_ITERATOR(IdentityContainer::const_iterator);
 
 BOOST_AUTO_TEST_SUITE(Security)
-BOOST_AUTO_TEST_SUITE(Pib)
 BOOST_FIXTURE_TEST_SUITE(TestIdentityContainer, PibDataFixture)
 
 BOOST_AUTO_TEST_CASE(AddGetRemove)
@@ -74,7 +72,7 @@
     Identity identity2 = container.get(id2);
     BOOST_CHECK_EQUAL(identity1.getName(), id1);
     BOOST_CHECK_EQUAL(identity2.getName(), id2);
-    BOOST_CHECK_THROW(container.get(Name("/non-existing")), pib::Pib::Error);
+    BOOST_CHECK_THROW(container.get(Name("/non-existing")), Pib::Error);
   }
 
   {
@@ -150,10 +148,6 @@
 }
 
 BOOST_AUTO_TEST_SUITE_END() // TestIdentityContainer
-BOOST_AUTO_TEST_SUITE_END() // Pib
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace pib
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/pib/identity.t.cpp b/tests/unit/security/pib/identity.t.cpp
index be2d03b..70252d9 100644
--- a/tests/unit/security/pib/identity.t.cpp
+++ b/tests/unit/security/pib/identity.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2022 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -25,13 +25,11 @@
 #include "tests/boost-test.hpp"
 #include "tests/unit/security/pib/pib-data-fixture.hpp"
 
-namespace ndn {
-namespace security {
-namespace pib {
-namespace tests {
+namespace ndn::tests {
+
+using namespace ndn::security::pib;
 
 BOOST_AUTO_TEST_SUITE(Security)
-BOOST_AUTO_TEST_SUITE(Pib)
 BOOST_FIXTURE_TEST_SUITE(TestIdentity, PibDataFixture)
 
 BOOST_AUTO_TEST_CASE(ValidityChecking)
@@ -41,7 +39,7 @@
   BOOST_TEST(id == Identity());
   BOOST_CHECK_THROW(id.getName(), std::domain_error);
 
-  auto impl = std::make_shared<detail::IdentityImpl>(id1, makePibWithIdentity(id1));
+  auto impl = std::make_shared<IdentityImpl>(id1, makePibWithIdentity(id1));
   id = Identity(impl);
   BOOST_TEST(id);
   BOOST_TEST(id != Identity());
@@ -52,12 +50,12 @@
   BOOST_CHECK_THROW(id.getName(), std::domain_error);
 }
 
-// pib::Identity is a wrapper of pib::detail::IdentityImpl. Since the functionality
-// of IdentityImpl is already tested in identity-impl.t.cpp, we only test the shared
-// property of pib::Identity in this test case.
+// pib::Identity is a wrapper of pib::IdentityImpl. Since the functionality
+// of IdentityImpl is already tested in identity-impl.t.cpp, we only test
+// the shared property of pib::Identity in this test case.
 BOOST_AUTO_TEST_CASE(SharedImpl)
 {
-  auto impl = std::make_shared<detail::IdentityImpl>(id1, makePibWithIdentity(id1));
+  auto impl = std::make_shared<IdentityImpl>(id1, makePibWithIdentity(id1));
   Identity identity1(impl);
   Identity identity2(impl);
 
@@ -66,22 +64,18 @@
   BOOST_TEST(Identity() != identity2);
   BOOST_TEST(Identity() == Identity());
 
-  BOOST_CHECK_THROW(identity2.getKey(id1Key1Name), pib::Pib::Error);
+  BOOST_CHECK_THROW(identity2.getKey(id1Key1Name), Pib::Error);
   identity1.addKey(id1Key1, id1Key1Name);
   BOOST_TEST(identity2.getKey(id1Key1Name));
 
   identity2.removeKey(id1Key1Name);
-  BOOST_CHECK_THROW(identity1.getKey(id1Key1Name), pib::Pib::Error);
+  BOOST_CHECK_THROW(identity1.getKey(id1Key1Name), Pib::Error);
 
   identity1.setDefaultKey(id1Key1, id1Key1Name);
   BOOST_TEST(identity2.getDefaultKey().getName() == id1Key1Name);
 }
 
 BOOST_AUTO_TEST_SUITE_END() // TestIdentity
-BOOST_AUTO_TEST_SUITE_END() // Pib
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace pib
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/pib/impl/identity-impl.t.cpp b/tests/unit/security/pib/impl/identity-impl.t.cpp
index 3f38e0e..6b44993 100644
--- a/tests/unit/security/pib/impl/identity-impl.t.cpp
+++ b/tests/unit/security/pib/impl/identity-impl.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2022 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -24,18 +24,13 @@
 #include "tests/boost-test.hpp"
 #include "tests/unit/security/pib/pib-data-fixture.hpp"
 
-namespace ndn {
-namespace security {
-namespace pib {
-namespace detail {
-namespace tests {
+namespace ndn::tests {
+
+using namespace ndn::security::pib;
 
 BOOST_AUTO_TEST_SUITE(Security)
-BOOST_AUTO_TEST_SUITE(Pib)
 
-using pib::Pib;
-
-class IdentityImplFixture : public pib::tests::PibDataFixture
+class IdentityImplFixture : public PibDataFixture
 {
 protected:
   const shared_ptr<PibImpl> pibImpl = makePibWithIdentity(id1);
@@ -136,11 +131,6 @@
 }
 
 BOOST_AUTO_TEST_SUITE_END() // TestIdentityImpl
-BOOST_AUTO_TEST_SUITE_END() // Pib
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace detail
-} // namespace pib
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/pib/impl/key-impl.t.cpp b/tests/unit/security/pib/impl/key-impl.t.cpp
index 4cb960a..940974b 100644
--- a/tests/unit/security/pib/impl/key-impl.t.cpp
+++ b/tests/unit/security/pib/impl/key-impl.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2022 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -25,18 +25,13 @@
 #include "tests/key-chain-fixture.hpp"
 #include "tests/unit/security/pib/pib-data-fixture.hpp"
 
-namespace ndn {
-namespace security {
-namespace pib {
-namespace detail {
-namespace tests {
+namespace ndn::tests {
+
+using namespace ndn::security::pib;
 
 BOOST_AUTO_TEST_SUITE(Security)
-BOOST_AUTO_TEST_SUITE(Pib)
 
-using pib::Pib;
-
-class KeyImplFixture : public pib::tests::PibDataFixture
+class KeyImplFixture : public PibDataFixture
 {
 protected:
   const shared_ptr<PibImpl> pibImpl = makePibWithKey(id1Key1Name, id1Key1);
@@ -114,8 +109,7 @@
   BOOST_CHECK_THROW(key11.getDefaultCertificate(), Pib::Error);
 }
 
-class ReplaceFixture : public ndn::tests::KeyChainFixture,
-                       public KeyImplFixture
+class ReplaceFixture : public KeyChainFixture, public KeyImplFixture
 {
 };
 
@@ -126,8 +120,8 @@
 
   auto otherCert = id1Key1Cert1;
   SignatureInfo info;
-  info.setValidityPeriod(ValidityPeriod::makeRelative(-1_s, 10_s));
-  m_keyChain.sign(otherCert, SigningInfo().setSignatureInfo(info));
+  info.setValidityPeriod(security::ValidityPeriod::makeRelative(-1_s, 10_s));
+  m_keyChain.sign(otherCert, security::SigningInfo().setSignatureInfo(info));
   BOOST_TEST(otherCert.getName() == id1Key1Cert1.getName());
   BOOST_TEST(otherCert.getContent() == id1Key1Cert1.getContent());
   BOOST_TEST(otherCert != id1Key1Cert1);
@@ -162,11 +156,6 @@
 }
 
 BOOST_AUTO_TEST_SUITE_END() // TestKeyImpl
-BOOST_AUTO_TEST_SUITE_END() // Pib
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace detail
-} // namespace pib
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/pib/key-container.t.cpp b/tests/unit/security/pib/key-container.t.cpp
index b126bc2..84a4d3f 100644
--- a/tests/unit/security/pib/key-container.t.cpp
+++ b/tests/unit/security/pib/key-container.t.cpp
@@ -26,15 +26,13 @@
 #include "tests/boost-test.hpp"
 #include "tests/unit/security/pib/pib-data-fixture.hpp"
 
-namespace ndn {
-namespace security {
-namespace pib {
-namespace tests {
+namespace ndn::tests {
+
+using namespace ndn::security::pib;
 
 NDN_CXX_ASSERT_FORWARD_ITERATOR(KeyContainer::const_iterator);
 
 BOOST_AUTO_TEST_SUITE(Security)
-BOOST_AUTO_TEST_SUITE(Pib)
 BOOST_FIXTURE_TEST_SUITE(TestKeyContainer, PibDataFixture)
 
 BOOST_AUTO_TEST_CASE(AddGetRemove)
@@ -79,8 +77,8 @@
     BOOST_TEST(key1.getPublicKey() == id1Key1, boost::test_tools::per_element());
     BOOST_CHECK_EQUAL(key2.getName(), id1Key2Name);
     BOOST_TEST(key2.getPublicKey() == id1Key2, boost::test_tools::per_element());
-    Name id1Key3Name = constructKeyName(id1, name::Component("non-existing-id"));
-    BOOST_CHECK_THROW(container.get(id1Key3Name), pib::Pib::Error);
+    Name id1Key3Name = security::constructKeyName(id1, name::Component("non-existing-id"));
+    BOOST_CHECK_THROW(container.get(id1Key3Name), Pib::Error);
   }
 
   {
@@ -167,10 +165,6 @@
 }
 
 BOOST_AUTO_TEST_SUITE_END() // TestKeyContainer
-BOOST_AUTO_TEST_SUITE_END() // Pib
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace pib
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/pib/key.t.cpp b/tests/unit/security/pib/key.t.cpp
index 4d1da0c..5273436 100644
--- a/tests/unit/security/pib/key.t.cpp
+++ b/tests/unit/security/pib/key.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2022 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -25,13 +25,11 @@
 #include "tests/boost-test.hpp"
 #include "tests/unit/security/pib/pib-data-fixture.hpp"
 
-namespace ndn {
-namespace security {
-namespace pib {
-namespace tests {
+namespace ndn::tests {
+
+using namespace ndn::security::pib;
 
 BOOST_AUTO_TEST_SUITE(Security)
-BOOST_AUTO_TEST_SUITE(Pib)
 BOOST_FIXTURE_TEST_SUITE(TestKey, PibDataFixture)
 
 BOOST_AUTO_TEST_CASE(ValidityChecking)
@@ -41,8 +39,7 @@
   BOOST_TEST(key == Key());
   BOOST_CHECK_THROW(key.getName(), std::domain_error);
 
-  auto impl = std::make_shared<detail::KeyImpl>(id1Key1Name, id1Key1,
-                                                makePibWithKey(id1Key1Name, id1Key1));
+  auto impl = std::make_shared<KeyImpl>(id1Key1Name, id1Key1, makePibWithKey(id1Key1Name, id1Key1));
   key = Key(impl);
   BOOST_TEST(key);
   BOOST_TEST(key != Key());
@@ -53,13 +50,12 @@
   BOOST_CHECK_THROW(key.getName(), std::domain_error);
 }
 
-// pib::Key is a wrapper of pib::detail::KeyImpl. Since the functionality of KeyImpl is
-// already tested in key-impl.t.cpp, we only test the shared property of pib::Key in
-// this test case.
+// pib::Key is a wrapper of pib::KeyImpl. Since the functionality of KeyImpl is
+// already tested in key-impl.t.cpp, we only test the shared property of pib::Key
+// in this test case.
 BOOST_AUTO_TEST_CASE(SharedImpl)
 {
-  auto keyImpl = std::make_shared<detail::KeyImpl>(id1Key1Name, id1Key1,
-                                                   makePibWithKey(id1Key1Name, id1Key1));
+  auto keyImpl = std::make_shared<KeyImpl>(id1Key1Name, id1Key1, makePibWithKey(id1Key1Name, id1Key1));
   Key key1(keyImpl);
   Key key2(keyImpl);
 
@@ -68,12 +64,12 @@
   BOOST_TEST(Key() != key2);
   BOOST_TEST(Key() == Key());
 
-  BOOST_CHECK_THROW(key2.getCertificate(id1Key1Cert1.getName()), pib::Pib::Error);
+  BOOST_CHECK_THROW(key2.getCertificate(id1Key1Cert1.getName()), Pib::Error);
   key1.addCertificate(id1Key1Cert1);
   BOOST_TEST(key2.getCertificate(id1Key1Cert1.getName()) == id1Key1Cert1);
 
   key2.removeCertificate(id1Key1Cert1.getName());
-  BOOST_CHECK_THROW(key1.getCertificate(id1Key1Cert1.getName()), pib::Pib::Error);
+  BOOST_CHECK_THROW(key1.getCertificate(id1Key1Cert1.getName()), Pib::Error);
 
   key1.setDefaultCertificate(id1Key1Cert1);
   BOOST_TEST(key2.getDefaultCertificate() == id1Key1Cert1);
@@ -81,6 +77,10 @@
 
 BOOST_AUTO_TEST_CASE(Helpers)
 {
+  using ndn::security::constructKeyName;
+  using ndn::security::isValidKeyName;
+  using ndn::security::extractIdentityFromKeyName;
+
   BOOST_CHECK_EQUAL(constructKeyName("/hello", name::Component("world")), "/hello/KEY/world");
 
   BOOST_CHECK_EQUAL(isValidKeyName("/hello"), false);
@@ -98,10 +98,6 @@
 }
 
 BOOST_AUTO_TEST_SUITE_END() // TestKey
-BOOST_AUTO_TEST_SUITE_END() // Pib
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace pib
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/pib/pib-data-fixture.cpp b/tests/unit/security/pib/pib-data-fixture.cpp
index 488d11e..dde1d8b 100644
--- a/tests/unit/security/pib/pib-data-fixture.cpp
+++ b/tests/unit/security/pib/pib-data-fixture.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2022 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -30,10 +30,10 @@
 
 // #include <iostream>
 
-namespace ndn {
-namespace security {
-namespace pib {
-namespace tests {
+namespace ndn::tests {
+
+using namespace ndn::security;
+using namespace ndn::security::pib;
 
 // class TestCertDataGenerator
 // {
@@ -95,8 +95,8 @@
 //   }
 
 // private:
-//   pib::PibMemory pib;
-//   Tpm tpm{"test", "test", make_unique<tpm::BackEndMem>()};
+//   PibMemory pib;
+//   Tpm tpm{"test:test", make_unique<tpm::BackEndMem>()};
 // };
 
 // // The test data can be generated using this test case
@@ -414,7 +414,4 @@
   return pib;
 }
 
-} // namespace tests
-} // namespace pib
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/pib/pib-data-fixture.hpp b/tests/unit/security/pib/pib-data-fixture.hpp
index 64c8652..7fcdebb 100644
--- a/tests/unit/security/pib/pib-data-fixture.hpp
+++ b/tests/unit/security/pib/pib-data-fixture.hpp
@@ -25,20 +25,19 @@
 #include "ndn-cxx/security/certificate.hpp"
 #include "ndn-cxx/security/pib/pib-impl.hpp"
 
-namespace ndn {
-namespace security {
-namespace pib {
-namespace tests {
+namespace ndn::tests {
+
+using ndn::security::Certificate;
 
 class PibDataFixture
 {
 public:
   PibDataFixture();
 
-  [[nodiscard]] static shared_ptr<PibImpl>
+  [[nodiscard]] static shared_ptr<security::pib::PibImpl>
   makePibWithIdentity(const Name& idName);
 
-  [[nodiscard]] static shared_ptr<PibImpl>
+  [[nodiscard]] static shared_ptr<security::pib::PibImpl>
   makePibWithKey(const Name& keyName, span<const uint8_t> key);
 
 public:
@@ -65,9 +64,6 @@
   Buffer id2Key2;
 };
 
-} // namespace tests
-} // namespace pib
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
 
 #endif // NDN_CXX_TESTS_UNIT_SECURITY_PIB_PIB_DATA_FIXTURE_HPP
diff --git a/tests/unit/security/pib/pib-impl.t.cpp b/tests/unit/security/pib/pib-impl.t.cpp
index d88bad6..b26109d 100644
--- a/tests/unit/security/pib/pib-impl.t.cpp
+++ b/tests/unit/security/pib/pib-impl.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2022 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -29,17 +29,13 @@
 #include <boost/filesystem.hpp>
 #include <boost/mpl/vector.hpp>
 
-namespace ndn {
-namespace security {
-namespace pib {
-namespace tests {
+namespace ndn::tests {
+
+using namespace ndn::security::pib;
 
 BOOST_AUTO_TEST_SUITE(Security)
-BOOST_AUTO_TEST_SUITE(Pib)
 BOOST_AUTO_TEST_SUITE(TestPibImpl)
 
-using pib::Pib;
-
 class PibMemoryFixture : public PibDataFixture
 {
 public:
@@ -336,10 +332,6 @@
 }
 
 BOOST_AUTO_TEST_SUITE_END() // TestPibImpl
-BOOST_AUTO_TEST_SUITE_END() // Pib
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace pib
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/pib/pib.t.cpp b/tests/unit/security/pib/pib.t.cpp
index 8d668e5..3a665c3 100644
--- a/tests/unit/security/pib/pib.t.cpp
+++ b/tests/unit/security/pib/pib.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2022 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -25,17 +25,13 @@
 #include "tests/boost-test.hpp"
 #include "tests/unit/security/pib/pib-data-fixture.hpp"
 
-namespace ndn {
-namespace security {
-namespace pib {
-namespace tests {
+namespace ndn::tests {
+
+using namespace ndn::security::pib;
 
 BOOST_AUTO_TEST_SUITE(Security)
-BOOST_AUTO_TEST_SUITE(Pib)
 BOOST_FIXTURE_TEST_SUITE(TestPib, PibDataFixture)
 
-using pib::Pib;
-
 BOOST_AUTO_TEST_CASE(TpmLocator)
 {
   Pib pib("pib-memory:", make_shared<PibMemory>());
@@ -116,10 +112,6 @@
 }
 
 BOOST_AUTO_TEST_SUITE_END() // TestPib
-BOOST_AUTO_TEST_SUITE_END() // Pib
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace pib
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/safe-bag.t.cpp b/tests/unit/security/safe-bag.t.cpp
index ade7f69..9f9b00d 100644
--- a/tests/unit/security/safe-bag.t.cpp
+++ b/tests/unit/security/safe-bag.t.cpp
@@ -25,9 +25,9 @@
 
 #include "tests/boost-test.hpp"
 
-namespace ndn {
-namespace security {
-namespace tests {
+namespace ndn::tests {
+
+using ndn::security::SafeBag;
 
 BOOST_CONCEPT_ASSERT((WireEncodable<SafeBag>));
 BOOST_CONCEPT_ASSERT((WireDecodable<SafeBag>));
@@ -162,6 +162,4 @@
 BOOST_AUTO_TEST_SUITE_END() // TestSafeBag
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/signing-helpers.t.cpp b/tests/unit/security/signing-helpers.t.cpp
index a515c16..c7065a2 100644
--- a/tests/unit/security/signing-helpers.t.cpp
+++ b/tests/unit/security/signing-helpers.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2020 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -23,9 +23,9 @@
 
 #include "tests/boost-test.hpp"
 
-namespace ndn {
-namespace security {
-namespace tests {
+namespace ndn::tests {
+
+using ndn::security::SigningInfo;
 
 BOOST_AUTO_TEST_SUITE(Security)
 BOOST_AUTO_TEST_SUITE(TestSigningHelpers)
@@ -64,6 +64,4 @@
 BOOST_AUTO_TEST_SUITE_END() // TestSigningHelpers
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/signing-info.t.cpp b/tests/unit/security/signing-info.t.cpp
index 87c347f..a1aee15 100644
--- a/tests/unit/security/signing-info.t.cpp
+++ b/tests/unit/security/signing-info.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2022 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -27,9 +27,9 @@
 #include <boost/lexical_cast.hpp>
 #include <sstream>
 
-namespace ndn {
-namespace security {
-namespace tests {
+namespace ndn::tests {
+
+using namespace ndn::security;
 
 BOOST_AUTO_TEST_SUITE(Security)
 BOOST_AUTO_TEST_SUITE(TestSigningInfo)
@@ -288,6 +288,4 @@
 BOOST_AUTO_TEST_SUITE_END() // TestSigningInfo
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/tpm/back-end-wrapper-file.hpp b/tests/unit/security/tpm/back-end-wrapper-file.hpp
index 2da77aa..6d8a663 100644
--- a/tests/unit/security/tpm/back-end-wrapper-file.hpp
+++ b/tests/unit/security/tpm/back-end-wrapper-file.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2021 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -26,10 +26,7 @@
 
 #include <boost/filesystem.hpp>
 
-namespace ndn {
-namespace security {
-namespace tpm {
-namespace tests {
+namespace ndn::tests {
 
 /**
  * @brief A wrapper of tpm::BackEndFile for unit test template.
@@ -39,7 +36,7 @@
 public:
   BackEndWrapperFile()
     : m_tmpPath(boost::filesystem::path(UNIT_TESTS_TMPDIR) / "TpmBackEndFile")
-    , m_impl(make_unique<BackEndFile>(m_tmpPath.string()))
+    , m_impl(make_unique<security::tpm::BackEndFile>(m_tmpPath.string()))
   {
   }
 
@@ -48,7 +45,7 @@
     boost::filesystem::remove_all(m_tmpPath);
   }
 
-  BackEnd&
+  security::tpm::BackEnd&
   getTpm()
   {
     return *m_impl;
@@ -62,12 +59,9 @@
 
 private:
   const boost::filesystem::path m_tmpPath;
-  const unique_ptr<BackEnd> m_impl;
+  const unique_ptr<security::tpm::BackEnd> m_impl;
 };
 
-} // namespace tests
-} // namespace tpm
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
 
 #endif // NDN_CXX_TESTS_UNIT_SECURITY_TPM_BACK_END_WRAPPER_FILE_HPP
diff --git a/tests/unit/security/tpm/back-end-wrapper-mem.hpp b/tests/unit/security/tpm/back-end-wrapper-mem.hpp
index 8de2b12..20dae82 100644
--- a/tests/unit/security/tpm/back-end-wrapper-mem.hpp
+++ b/tests/unit/security/tpm/back-end-wrapper-mem.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2021 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -24,10 +24,7 @@
 
 #include "ndn-cxx/security/tpm/impl/back-end-mem.hpp"
 
-namespace ndn {
-namespace security {
-namespace tpm {
-namespace tests {
+namespace ndn::tests {
 
 /**
  * @brief A wrapper of tpm::BackEndMem for unit test template.
@@ -36,11 +33,11 @@
 {
 public:
   BackEndWrapperMem()
-    : m_impl(make_unique<BackEndMem>())
+    : m_impl(make_unique<security::tpm::BackEndMem>())
   {
   }
 
-  BackEnd&
+  security::tpm::BackEnd&
   getTpm()
   {
     return *m_impl;
@@ -53,12 +50,9 @@
   }
 
 private:
-  const unique_ptr<BackEnd> m_impl;
+  const unique_ptr<security::tpm::BackEnd> m_impl;
 };
 
-} // namespace tests
-} // namespace tpm
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
 
 #endif // NDN_CXX_TESTS_UNIT_SECURITY_TPM_BACK_END_WRAPPER_MEM_HPP
diff --git a/tests/unit/security/tpm/back-end-wrapper-osx.hpp b/tests/unit/security/tpm/back-end-wrapper-osx.hpp
index c459c47..542c319 100644
--- a/tests/unit/security/tpm/back-end-wrapper-osx.hpp
+++ b/tests/unit/security/tpm/back-end-wrapper-osx.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2021 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -27,10 +27,7 @@
 
 #include <cstdlib>
 
-namespace ndn {
-namespace security {
-namespace tpm {
-namespace tests {
+namespace ndn::tests {
 
 /**
  * @brief A wrapper of tpm::BackEndOsx for unit test template.
@@ -52,7 +49,7 @@
     else
       unsetenv("HOME");
 
-    m_impl = make_unique<BackEndOsx>();
+    m_impl = make_unique<security::tpm::BackEndOsx>();
   }
 
   ~BackEndWrapperOsx()
@@ -63,7 +60,7 @@
       unsetenv("HOME");
   }
 
-  BackEnd&
+  security::tpm::BackEnd&
   getTpm()
   {
     return *m_impl;
@@ -77,12 +74,9 @@
 
 private:
   std::string m_HOME;
-  unique_ptr<BackEnd> m_impl;
+  unique_ptr<security::tpm::BackEnd> m_impl;
 };
 
-} // namespace tests
-} // namespace tpm
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
 
 #endif // NDN_CXX_TESTS_UNIT_SECURITY_TPM_BACK_END_WRAPPER_OSX_HPP
diff --git a/tests/unit/security/tpm/back-end.t.cpp b/tests/unit/security/tpm/back-end.t.cpp
index 78f09e3..34d79b4 100644
--- a/tests/unit/security/tpm/back-end.t.cpp
+++ b/tests/unit/security/tpm/back-end.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2022 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -41,16 +41,14 @@
 #include <boost/mpl/vector.hpp>
 #include <set>
 
-namespace ndn {
-namespace security {
-namespace tpm {
-namespace tests {
+namespace ndn::tests {
+
+using namespace ndn::security;
+using ndn::security::tpm::BackEnd;
+using ndn::security::tpm::KeyHandle;
 
 BOOST_AUTO_TEST_SUITE(Security)
-BOOST_AUTO_TEST_SUITE(Tpm)
-BOOST_AUTO_TEST_SUITE(TestBackEnd)
-
-using tpm::Tpm;
+BOOST_AUTO_TEST_SUITE(TestTpmBackEnd)
 
 using TestBackEnds = boost::mpl::vector<
 #if defined(NDN_CXX_HAVE_OSX_FRAMEWORKS) && defined(NDN_CXX_WITH_OSX_KEYCHAIN)
@@ -354,11 +352,7 @@
   }
 }
 
-BOOST_AUTO_TEST_SUITE_END() // TestBackEnd
-BOOST_AUTO_TEST_SUITE_END() // Tpm
+BOOST_AUTO_TEST_SUITE_END() // TestTpmBackEnd
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace tpm
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/transform.t.cpp b/tests/unit/security/transform.t.cpp
deleted file mode 100644
index 901839b..0000000
--- a/tests/unit/security/transform.t.cpp
+++ /dev/null
@@ -1,83 +0,0 @@
-/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
-/*
- * Copyright (c) 2013-2019 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 "ndn-cxx/security/transform.hpp"
-
-#include "tests/boost-test.hpp"
-
-namespace ndn {
-namespace security {
-namespace tests {
-
-BOOST_AUTO_TEST_SUITE(Security)
-BOOST_AUTO_TEST_SUITE(TestTransform)
-
-BOOST_AUTO_TEST_CASE(SymbolVisibility)
-{
-  transform::BufferSource* bufferSource = nullptr;
-  BOOST_CHECK(bufferSource == nullptr);
-
-  transform::StreamSource* streamSource = nullptr;
-  BOOST_CHECK(streamSource == nullptr);
-
-  transform::StepSource* stepSource = nullptr;
-  BOOST_CHECK(stepSource == nullptr);
-
-  transform::BoolSink* boolSink = nullptr;
-  BOOST_CHECK(boolSink == nullptr);
-
-  transform::StreamSink* streamSink = nullptr;
-  BOOST_CHECK(streamSink == nullptr);
-
-  transform::HexEncode* hexEncode = nullptr;
-  BOOST_CHECK(hexEncode == nullptr);
-
-  transform::StripSpace* stripSpace = nullptr;
-  BOOST_CHECK(stripSpace == nullptr);
-
-  transform::HexDecode* hexDecode = nullptr;
-  BOOST_CHECK(hexDecode == nullptr);
-
-  transform::Base64Encode* base64Encode = nullptr;
-  BOOST_CHECK(base64Encode == nullptr);
-
-  transform::Base64Decode* base64Decode = nullptr;
-  BOOST_CHECK(base64Decode == nullptr);
-
-  transform::DigestFilter* digestFilter = nullptr;
-  BOOST_CHECK(digestFilter == nullptr);
-
-  transform::BlockCipher* blockCipher = nullptr;
-  BOOST_CHECK(blockCipher == nullptr);
-
-  transform::SignerFilter* signerFilter = nullptr;
-  BOOST_CHECK(signerFilter == nullptr);
-
-  transform::VerifierFilter* verifierFilter = nullptr;
-  BOOST_CHECK(verifierFilter == nullptr);
-}
-
-BOOST_AUTO_TEST_SUITE_END() // TestTransform
-BOOST_AUTO_TEST_SUITE_END() // Security
-
-} // namespace tests
-} // namespace security
-} // namespace ndn
diff --git a/tests/unit/security/transform/base64-decode.t.cpp b/tests/unit/security/transform/base64-decode.t.cpp
index 5d89fe6..f180624 100644
--- a/tests/unit/security/transform/base64-decode.t.cpp
+++ b/tests/unit/security/transform/base64-decode.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2021 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -27,10 +27,9 @@
 
 #include "tests/boost-test.hpp"
 
-namespace ndn {
-namespace security {
-namespace transform {
-namespace tests {
+namespace ndn::tests {
+
+using namespace ndn::security::transform;
 
 BOOST_AUTO_TEST_SUITE(Security)
 BOOST_AUTO_TEST_SUITE(Transform)
@@ -173,7 +172,4 @@
 BOOST_AUTO_TEST_SUITE_END() // Transform
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace transform
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/transform/base64-encode.t.cpp b/tests/unit/security/transform/base64-encode.t.cpp
index 7b4aa47..c25ecba 100644
--- a/tests/unit/security/transform/base64-encode.t.cpp
+++ b/tests/unit/security/transform/base64-encode.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2021 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -28,10 +28,9 @@
 
 #include "tests/boost-test.hpp"
 
-namespace ndn {
-namespace security {
-namespace transform {
-namespace tests {
+namespace ndn::tests {
+
+using namespace ndn::security::transform;
 
 BOOST_AUTO_TEST_SUITE(Security)
 BOOST_AUTO_TEST_SUITE(Transform)
@@ -171,7 +170,4 @@
 BOOST_AUTO_TEST_SUITE_END() // Transform
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace transform
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/transform/block-cipher.t.cpp b/tests/unit/security/transform/block-cipher.t.cpp
index d8b3c3b..cd857c1 100644
--- a/tests/unit/security/transform/block-cipher.t.cpp
+++ b/tests/unit/security/transform/block-cipher.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2022 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -27,10 +27,9 @@
 
 #include "tests/boost-test.hpp"
 
-namespace ndn {
-namespace security {
-namespace transform {
-namespace tests {
+namespace ndn::tests {
+
+using namespace ndn::security::transform;
 
 BOOST_AUTO_TEST_SUITE(Security)
 BOOST_AUTO_TEST_SUITE(Transform)
@@ -106,7 +105,4 @@
 BOOST_AUTO_TEST_SUITE_END() // Transform
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace transform
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/transform/bool-sink.t.cpp b/tests/unit/security/transform/bool-sink.t.cpp
index a7640c6..be10b13 100644
--- a/tests/unit/security/transform/bool-sink.t.cpp
+++ b/tests/unit/security/transform/bool-sink.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2021 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -23,10 +23,9 @@
 
 #include "tests/boost-test.hpp"
 
-namespace ndn {
-namespace security {
-namespace transform {
-namespace tests {
+namespace ndn::tests {
+
+using namespace ndn::security::transform;
 
 BOOST_AUTO_TEST_SUITE(Security)
 BOOST_AUTO_TEST_SUITE(Transform)
@@ -41,7 +40,7 @@
   BOOST_CHECK_EQUAL(sink1.write({in1 + 1, 1}), 1);
   sink1.end();
   BOOST_CHECK_EQUAL(value1, false);
-  BOOST_CHECK_THROW(sink1.write({in1 + 1, 1}), transform::Error);
+  BOOST_CHECK_THROW(sink1.write({in1 + 1, 1}), Error);
 
   const uint8_t in2[] = {0x01, 0x00};
   bool value2 = false;
@@ -50,14 +49,11 @@
   BOOST_CHECK_EQUAL(sink2.write({in2 + 1, 1}), 1);
   sink2.end();
   BOOST_CHECK_EQUAL(value2, true);
-  BOOST_CHECK_THROW(sink2.write({in2 + 1, 1}), transform::Error);
+  BOOST_CHECK_THROW(sink2.write({in2 + 1, 1}), Error);
 }
 
 BOOST_AUTO_TEST_SUITE_END() // TestBoolSink
 BOOST_AUTO_TEST_SUITE_END() // Transform
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace transform
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/transform/buffer-source.t.cpp b/tests/unit/security/transform/buffer-source.t.cpp
index f957282..aa27644 100644
--- a/tests/unit/security/transform/buffer-source.t.cpp
+++ b/tests/unit/security/transform/buffer-source.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2022 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -24,10 +24,9 @@
 
 #include "tests/boost-test.hpp"
 
-namespace ndn {
-namespace security {
-namespace transform {
-namespace tests {
+namespace ndn::tests {
+
+using namespace ndn::security::transform;
 
 BOOST_AUTO_TEST_SUITE(Security)
 BOOST_AUTO_TEST_SUITE(Transform)
@@ -91,7 +90,4 @@
 BOOST_AUTO_TEST_SUITE_END() // Transform
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace transform
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/transform/digest-filter.t.cpp b/tests/unit/security/transform/digest-filter.t.cpp
index 08f85cf..c414d17 100644
--- a/tests/unit/security/transform/digest-filter.t.cpp
+++ b/tests/unit/security/transform/digest-filter.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2022 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -30,10 +30,9 @@
 
 #include <openssl/evp.h>
 
-namespace ndn {
-namespace security {
-namespace transform {
-namespace tests {
+namespace ndn::tests {
+
+using namespace ndn::security::transform;
 
 BOOST_AUTO_TEST_SUITE(Security)
 BOOST_AUTO_TEST_SUITE(Transform)
@@ -215,7 +214,4 @@
 BOOST_AUTO_TEST_SUITE_END() // Transform
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace transform
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/transform/hex-decode.t.cpp b/tests/unit/security/transform/hex-decode.t.cpp
index 23ca9aa..51a2672 100644
--- a/tests/unit/security/transform/hex-decode.t.cpp
+++ b/tests/unit/security/transform/hex-decode.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2021 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -28,10 +28,9 @@
 
 #include "tests/boost-test.hpp"
 
-namespace ndn {
-namespace security {
-namespace transform {
-namespace tests {
+namespace ndn::tests {
+
+using namespace ndn::security::transform;
 
 BOOST_AUTO_TEST_SUITE(Security)
 BOOST_AUTO_TEST_SUITE(Transform)
@@ -262,11 +261,11 @@
 {
   const std::string in1 = "0001020304050";
   OBufferStream os1;
-  BOOST_CHECK_THROW(bufferSource(in1) >> hexDecode() >> streamSink(os1), transform::Error);
+  BOOST_CHECK_THROW(bufferSource(in1) >> hexDecode() >> streamSink(os1), Error);
 
   const std::string in2 = "0001020304xy";
   OBufferStream os2;
-  BOOST_CHECK_THROW(bufferSource(in2) >> hexDecode() >> streamSink(os2), transform::Error);
+  BOOST_CHECK_THROW(bufferSource(in2) >> hexDecode() >> streamSink(os2), Error);
 }
 
 BOOST_AUTO_TEST_CASE(EmptyInput)
@@ -283,7 +282,4 @@
 BOOST_AUTO_TEST_SUITE_END() // Transform
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace transform
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/transform/hex-encode.t.cpp b/tests/unit/security/transform/hex-encode.t.cpp
index 8025c37..2a81b6a 100644
--- a/tests/unit/security/transform/hex-encode.t.cpp
+++ b/tests/unit/security/transform/hex-encode.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2021 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -27,10 +27,9 @@
 
 #include "tests/boost-test.hpp"
 
-namespace ndn {
-namespace security {
-namespace transform {
-namespace tests {
+namespace ndn::tests {
+
+using namespace ndn::security::transform;
 
 BOOST_AUTO_TEST_SUITE(Security)
 BOOST_AUTO_TEST_SUITE(Transform)
@@ -176,7 +175,4 @@
 BOOST_AUTO_TEST_SUITE_END() // Transform
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace transform
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/transform/private-key.t.cpp b/tests/unit/security/transform/private-key.t.cpp
index 077c2e3..f9a511d 100644
--- a/tests/unit/security/transform/private-key.t.cpp
+++ b/tests/unit/security/transform/private-key.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2022 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -38,10 +38,9 @@
 #include <boost/mpl/vector.hpp>
 #include <sstream>
 
-namespace ndn {
-namespace security {
-namespace transform {
-namespace tests {
+namespace ndn::tests {
+
+using namespace ndn::security::transform;
 
 BOOST_AUTO_TEST_SUITE(Security)
 BOOST_AUTO_TEST_SUITE(Transform)
@@ -716,7 +715,4 @@
 BOOST_AUTO_TEST_SUITE_END() // Transform
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace transform
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/transform/public-key.t.cpp b/tests/unit/security/transform/public-key.t.cpp
index 655811c..31970c4 100644
--- a/tests/unit/security/transform/public-key.t.cpp
+++ b/tests/unit/security/transform/public-key.t.cpp
@@ -32,10 +32,9 @@
 
 #include <sstream>
 
-namespace ndn {
-namespace security {
-namespace transform {
-namespace tests {
+namespace ndn::tests {
+
+using namespace ndn::security::transform;
 
 BOOST_AUTO_TEST_SUITE(Security)
 BOOST_AUTO_TEST_SUITE(Transform)
@@ -151,7 +150,4 @@
 BOOST_AUTO_TEST_SUITE_END() // Transform
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace transform
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/transform/signer-filter.t.cpp b/tests/unit/security/transform/signer-filter.t.cpp
index cad6f04..ad3b788 100644
--- a/tests/unit/security/transform/signer-filter.t.cpp
+++ b/tests/unit/security/transform/signer-filter.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2022 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -31,10 +31,9 @@
 
 #include "tests/boost-test.hpp"
 
-namespace ndn {
-namespace security {
-namespace transform {
-namespace tests {
+namespace ndn::tests {
+
+using namespace ndn::security::transform;
 
 BOOST_AUTO_TEST_SUITE(Security)
 BOOST_AUTO_TEST_SUITE(Transform)
@@ -92,7 +91,7 @@
   bufferSource(data) >> signerFilter(DigestAlgorithm::SHA256, sKey) >> streamSink(os2);
   auto sig = os2.buf();
 
-  BOOST_TEST(verifySignature({data}, *sig, *pubKey));
+  BOOST_TEST(security::verifySignature({data}, *sig, *pubKey));
 }
 
 BOOST_AUTO_TEST_CASE(Ecdsa)
@@ -130,7 +129,7 @@
   bufferSource(data) >> signerFilter(DigestAlgorithm::SHA256, sKey) >> streamSink(os2);
   auto sig = os2.buf();
 
-  BOOST_TEST(verifySignature({data}, *sig, *pubKey));
+  BOOST_TEST(security::verifySignature({data}, *sig, *pubKey));
 }
 
 BOOST_AUTO_TEST_SUITE(Hmac)
@@ -244,7 +243,4 @@
 BOOST_AUTO_TEST_SUITE_END() // Transform
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace transform
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/transform/step-source.t.cpp b/tests/unit/security/transform/step-source.t.cpp
index 0179011..c950716 100644
--- a/tests/unit/security/transform/step-source.t.cpp
+++ b/tests/unit/security/transform/step-source.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2021 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -26,10 +26,9 @@
 
 #include <sstream>
 
-namespace ndn {
-namespace security {
-namespace transform {
-namespace tests {
+namespace ndn::tests {
+
+using namespace ndn::security::transform;
 
 BOOST_AUTO_TEST_SUITE(Security)
 BOOST_AUTO_TEST_SUITE(Transform)
@@ -69,7 +68,7 @@
   BOOST_CHECK_EQUAL(ss.write({buf + 960, 320}), 320);
   ss.end();
 
-  BOOST_CHECK_THROW(ss.write({buf + 960, 320}), transform::Error);
+  BOOST_CHECK_THROW(ss.write({buf + 960, 320}), Error);
   BOOST_CHECK_EQUAL(os.str(), input);
 }
 
@@ -87,7 +86,4 @@
 BOOST_AUTO_TEST_SUITE_END() // Transform
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace transform
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/transform/stream-sink.t.cpp b/tests/unit/security/transform/stream-sink.t.cpp
index f58bece..b79012d 100644
--- a/tests/unit/security/transform/stream-sink.t.cpp
+++ b/tests/unit/security/transform/stream-sink.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2021 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -23,10 +23,9 @@
 
 #include "tests/boost-test.hpp"
 
-namespace ndn {
-namespace security {
-namespace transform {
-namespace tests {
+namespace ndn::tests {
+
+using namespace ndn::security::transform;
 
 BOOST_AUTO_TEST_SUITE(Security)
 BOOST_AUTO_TEST_SUITE(Transform)
@@ -48,14 +47,11 @@
 
   std::string out = os.str();
   BOOST_CHECK_EQUAL_COLLECTIONS(in, in + sizeof(in), out.begin(), out.end());
-  BOOST_CHECK_THROW(sink.write({in + 8, 8}), transform::Error);
+  BOOST_CHECK_THROW(sink.write({in + 8, 8}), Error);
 }
 
 BOOST_AUTO_TEST_SUITE_END() // TestStreamSink
 BOOST_AUTO_TEST_SUITE_END() // Transform
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace transform
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/transform/stream-source.t.cpp b/tests/unit/security/transform/stream-source.t.cpp
index 1446bc9..e20ff23 100644
--- a/tests/unit/security/transform/stream-source.t.cpp
+++ b/tests/unit/security/transform/stream-source.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2018 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -27,10 +27,9 @@
 #include <boost/mpl/integral_c.hpp>
 #include <boost/mpl/vector.hpp>
 
-namespace ndn {
-namespace security {
-namespace transform {
-namespace tests {
+namespace ndn::tests {
+
+using namespace ndn::security::transform;
 
 BOOST_AUTO_TEST_SUITE(Security)
 BOOST_AUTO_TEST_SUITE(Transform)
@@ -77,24 +76,21 @@
   BOOST_CHECK_EQUAL(os.str(), "");
 }
 
-typedef boost::mpl::vector<
+using BadBits = boost::mpl::vector<
   boost::mpl::integral_c<std::ios_base::iostate, std::ios_base::badbit>,
   boost::mpl::integral_c<std::ios_base::iostate, std::ios_base::failbit>
-> BadBits;
+>;
 
 BOOST_AUTO_TEST_CASE_TEMPLATE(BadStream, BadBit, BadBits)
 {
   std::stringstream is;
   is.setstate(BadBit::value);
   std::stringstream os;
-  BOOST_CHECK_THROW(streamSource(is) >> streamSink(os), transform::Error);
+  BOOST_CHECK_THROW(streamSource(is) >> streamSink(os), Error);
 }
 
 BOOST_AUTO_TEST_SUITE_END() // TestStreamSource
 BOOST_AUTO_TEST_SUITE_END() // Transform
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace transform
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/transform/strip-space.t.cpp b/tests/unit/security/transform/strip-space.t.cpp
index cd73270..cbc406d 100644
--- a/tests/unit/security/transform/strip-space.t.cpp
+++ b/tests/unit/security/transform/strip-space.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2021 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -27,10 +27,9 @@
 
 #include "tests/boost-test.hpp"
 
-namespace ndn {
-namespace security {
-namespace transform {
-namespace tests {
+namespace ndn::tests {
+
+using namespace ndn::security::transform;
 
 BOOST_AUTO_TEST_SUITE(Security)
 BOOST_AUTO_TEST_SUITE(Transform)
@@ -72,7 +71,4 @@
 BOOST_AUTO_TEST_SUITE_END() // Transform
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace transform
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/transform/verifier-filter.t.cpp b/tests/unit/security/transform/verifier-filter.t.cpp
index ef986b1..e04415c 100644
--- a/tests/unit/security/transform/verifier-filter.t.cpp
+++ b/tests/unit/security/transform/verifier-filter.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2022 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -35,10 +35,9 @@
 
 #include <openssl/opensslv.h>
 
-namespace ndn {
-namespace security {
-namespace transform {
-namespace tests {
+namespace ndn::tests {
+
+using namespace ndn::security::transform;
 
 BOOST_AUTO_TEST_SUITE(Security)
 BOOST_AUTO_TEST_SUITE(Transform)
@@ -188,7 +187,4 @@
 BOOST_AUTO_TEST_SUITE_END() // Transform
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace transform
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/trust-anchor-container.t.cpp b/tests/unit/security/trust-anchor-container.t.cpp
index 09825db..0e76214 100644
--- a/tests/unit/security/trust-anchor-container.t.cpp
+++ b/tests/unit/security/trust-anchor-container.t.cpp
@@ -27,17 +27,12 @@
 
 #include <boost/filesystem/operations.hpp>
 
-namespace ndn {
-namespace security {
-inline namespace v2 {
-namespace tests {
+namespace ndn::tests {
 
-using namespace ndn::tests;
+using namespace ndn::security;
 
-/**
- * This fixture creates a directory and prepares two certificates.
- * cert1 is written to a file under the directory, while cert2 is not.
- */
+// This fixture creates a directory and prepares two certificates.
+// cert1 is written to a file under the directory, while cert2 is not.
 class TrustAnchorContainerFixture : public ClockFixture, public KeyChainFixture
 {
 public:
@@ -196,7 +191,4 @@
 BOOST_AUTO_TEST_SUITE_END() // TestTrustAnchorContainer
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // inline namespace v2
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/validation-error.t.cpp b/tests/unit/security/validation-error.t.cpp
index c4a1a08..f59d6e7 100644
--- a/tests/unit/security/validation-error.t.cpp
+++ b/tests/unit/security/validation-error.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2022 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -25,10 +25,9 @@
 
 #include <boost/lexical_cast.hpp>
 
-namespace ndn {
-namespace security {
-inline namespace v2 {
-namespace tests {
+namespace ndn::tests {
+
+using ndn::security::ValidationError;
 
 BOOST_AUTO_TEST_SUITE(Security)
 BOOST_AUTO_TEST_SUITE(TestValidationError)
@@ -59,7 +58,4 @@
 BOOST_AUTO_TEST_SUITE_END() // TestValidationError
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // inline namespace v2
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/validation-policy-accept-all.t.cpp b/tests/unit/security/validation-policy-accept-all.t.cpp
index cd94cf7..ca86c86 100644
--- a/tests/unit/security/validation-policy-accept-all.t.cpp
+++ b/tests/unit/security/validation-policy-accept-all.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2020 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -26,16 +26,11 @@
 
 #include <boost/mpl/vector.hpp>
 
-namespace ndn {
-namespace security {
-inline namespace v2 {
-namespace tests {
-
-using namespace ndn::tests;
+namespace ndn::tests {
 
 BOOST_AUTO_TEST_SUITE(Security)
 
-class ValidationPolicyAcceptAllFixture : public ValidatorFixture<ValidationPolicyAcceptAll>
+class ValidationPolicyAcceptAllFixture : public ValidatorFixture<security::ValidationPolicyAcceptAll>
 {
 public:
   ValidationPolicyAcceptAllFixture()
@@ -50,7 +45,7 @@
 
 BOOST_FIXTURE_TEST_SUITE(TestValidationPolicyAcceptAll, ValidationPolicyAcceptAllFixture)
 
-typedef boost::mpl::vector<Interest, Data> Packets;
+using Packets = boost::mpl::vector<Interest, Data>;
 
 BOOST_AUTO_TEST_CASE_TEMPLATE(Validate, Packet, Packets)
 {
@@ -71,7 +66,4 @@
 BOOST_AUTO_TEST_SUITE_END() // TestValidationPolicyAcceptAll
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // inline namespace v2
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/validation-policy-command-interest.t.cpp b/tests/unit/security/validation-policy-command-interest.t.cpp
index 971b509..ac690e7 100644
--- a/tests/unit/security/validation-policy-command-interest.t.cpp
+++ b/tests/unit/security/validation-policy-command-interest.t.cpp
@@ -30,12 +30,9 @@
 
 #include <boost/mpl/vector.hpp>
 
-namespace ndn {
-namespace security {
-inline namespace v2 {
-namespace tests {
+namespace ndn::tests {
 
-using namespace ndn::tests;
+using namespace ndn::security;
 
 BOOST_AUTO_TEST_SUITE(Security)
 
@@ -535,7 +532,4 @@
 BOOST_AUTO_TEST_SUITE_END() // TestValidationPolicyCommandInterest
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // inline namespace v2
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/validation-policy-config.t.cpp b/tests/unit/security/validation-policy-config.t.cpp
index 83c6f52..07b98e9 100644
--- a/tests/unit/security/validation-policy-config.t.cpp
+++ b/tests/unit/security/validation-policy-config.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2022 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -30,14 +30,9 @@
 #include "tests/unit/security/validator-config/common.hpp"
 #include "tests/unit/security/validator-fixture.hpp"
 
-namespace ndn {
-namespace security {
-inline namespace v2 {
-namespace validator_config {
-namespace tests {
+namespace ndn::tests {
 
-using namespace ndn::tests;
-using namespace ndn::security::tests;
+using ndn::security::ValidationPolicyConfig;
 
 BOOST_AUTO_TEST_SUITE(Security)
 BOOST_AUTO_TEST_SUITE(TestValidationPolicyConfig)
@@ -760,6 +755,8 @@
 
 BOOST_FIXTURE_TEST_CASE(OrphanedPolicyLoad, HierarchicalValidatorFixture<ValidationPolicyConfig>) // Bug #4758
 {
+  using ndn::security::validator_config::Error;
+
   ValidationPolicyConfig policy1;
   BOOST_CHECK_THROW(policy1.load("trust-anchor { type any }", "test-config"), Error);
 
@@ -767,8 +764,7 @@
   BOOST_CHECK_THROW(policy1.load("trust-anchor { type any }", "test-config"), Error);
 
   ValidationPolicyConfig policy2;
-
-  std::string config = R"CONF(
+  const std::string config = R"CONF(
       trust-anchor
       {
         type dir
@@ -776,7 +772,6 @@
         refresh 1h
       }
     )CONF";
-
   // Inserting trust anchor would have triggered a segfault
   BOOST_CHECK_THROW(policy2.load(config, "test-config"), Error);
 }
@@ -784,8 +779,4 @@
 BOOST_AUTO_TEST_SUITE_END() // TestValidationPolicyConfig
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace validator_config
-} // inline namespace v2
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/validation-policy-signed-interest.t.cpp b/tests/unit/security/validation-policy-signed-interest.t.cpp
index 58f502e..ded8825 100644
--- a/tests/unit/security/validation-policy-signed-interest.t.cpp
+++ b/tests/unit/security/validation-policy-signed-interest.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2022 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -30,12 +30,9 @@
 
 #include <boost/mpl/vector.hpp>
 
-namespace ndn {
-namespace security {
-inline namespace v2 {
-namespace tests {
+namespace ndn::tests {
 
-using namespace ndn::tests;
+using namespace ndn::security;
 
 BOOST_AUTO_TEST_SUITE(Security)
 
@@ -525,7 +522,4 @@
 BOOST_AUTO_TEST_SUITE_END() // TestValidationPolicySignedInterest
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // inline namespace v2
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/validation-policy-simple-hierarchy.t.cpp b/tests/unit/security/validation-policy-simple-hierarchy.t.cpp
index 788a7c9..80fc58a 100644
--- a/tests/unit/security/validation-policy-simple-hierarchy.t.cpp
+++ b/tests/unit/security/validation-policy-simple-hierarchy.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2022 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -26,14 +26,11 @@
 
 #include <boost/mpl/vector.hpp>
 
-namespace ndn {
-namespace security {
-inline namespace v2 {
-namespace tests {
+namespace ndn::tests {
 
 BOOST_AUTO_TEST_SUITE(Security)
 BOOST_FIXTURE_TEST_SUITE(TestValidationPolicySimpleHierarchy,
-                         HierarchicalValidatorFixture<ValidationPolicySimpleHierarchy>)
+                         HierarchicalValidatorFixture<security::ValidationPolicySimpleHierarchy>)
 
 using Packets = boost::mpl::vector<InterestV03Pkt, DataPkt>;
 
@@ -125,7 +122,4 @@
 BOOST_AUTO_TEST_SUITE_END() // TestValidationPolicySimpleHierarchy
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // inline namespace v2
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/validation-policy.t.cpp b/tests/unit/security/validation-policy.t.cpp
index 3d76f62..3ff9fe8 100644
--- a/tests/unit/security/validation-policy.t.cpp
+++ b/tests/unit/security/validation-policy.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2022 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -24,16 +24,15 @@
 #include "tests/boost-test.hpp"
 #include "tests/key-chain-fixture.hpp"
 
-namespace ndn {
-namespace security {
-inline namespace v2 {
-namespace tests {
+namespace ndn::tests {
 
 BOOST_AUTO_TEST_SUITE(Security)
-BOOST_FIXTURE_TEST_SUITE(TestValidationPolicy, ndn::tests::KeyChainFixture)
+BOOST_FIXTURE_TEST_SUITE(TestValidationPolicy, KeyChainFixture)
 
 BOOST_AUTO_TEST_CASE(ExtractIdentityNameFromKeyLocator)
 {
+  using ndn::security::extractIdentityNameFromKeyLocator;
+
   auto id = m_keyChain.createIdentity("/random/identity");
   auto keyName = id.getDefaultKey().getName();
   auto certName = id.getDefaultKey().getDefaultCertificate().getName();
@@ -55,7 +54,4 @@
 BOOST_AUTO_TEST_SUITE_END() // TestValidationPolicy
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // inline namespace v2
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/validator-config.t.cpp b/tests/unit/security/validator-config.t.cpp
index 391879d..7cdfa53 100644
--- a/tests/unit/security/validator-config.t.cpp
+++ b/tests/unit/security/validator-config.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2022 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -29,11 +29,7 @@
 #include "tests/key-chain-fixture.hpp"
 #include "tests/unit/security/validator-config/common.hpp"
 
-namespace ndn {
-namespace security {
-namespace tests {
-
-using namespace ndn::tests;
+namespace ndn::tests {
 
 BOOST_AUTO_TEST_SUITE(Security)
 BOOST_FIXTURE_TEST_SUITE(TestValidatorConfig, KeyChainFixture)
@@ -42,12 +38,12 @@
 
 BOOST_AUTO_TEST_CASE(Construct)
 {
-  util::DummyClientFace face;
+  DummyClientFace face;
 
   ValidatorConfig v1(face);
   BOOST_CHECK_EQUAL(v1.m_policyConfig.m_isConfigured, false);
 
-  ValidatorConfig v2(make_unique<CertificateFetcherOffline>());
+  ValidatorConfig v2(make_unique<security::CertificateFetcherOffline>());
   BOOST_CHECK_EQUAL(v2.m_policyConfig.m_isConfigured, false);
 }
 
@@ -56,7 +52,7 @@
 public:
   ValidatorConfigFixture()
     : path(boost::filesystem::path(UNIT_TESTS_TMPDIR) / "security" / "validator-config")
-    , validator(make_unique<CertificateFetcherOffline>())
+    , validator(make_unique<security::CertificateFetcherOffline>())
   {
     boost::filesystem::create_directories(path);
     config = R"CONF(
@@ -118,11 +114,11 @@
 
 BOOST_AUTO_TEST_CASE(FromSection)
 {
-  validator.load(validator_config::tests::makeSection(config), "config-file-from-section");
+  validator.load(makeSection(config), "config-file-from-section");
   BOOST_CHECK_EQUAL(validator.m_policyConfig.m_isConfigured, true);
 
   // should reload policy
-  validator.load(validator_config::tests::makeSection(config), "config-file-from-section");
+  validator.load(makeSection(config), "config-file-from-section");
   BOOST_CHECK_EQUAL(validator.m_policyConfig.m_isConfigured, true);
 }
 
@@ -133,7 +129,7 @@
 {
   validator.load(configFile);
 
-  InterestSigner signer(m_keyChain);
+  security::InterestSigner signer(m_keyChain);
   auto i = signer.makeCommandInterest("/hello/world/CMD", signingWithSha256());
   size_t nValidated = 0, nFailed = 0;
 
@@ -155,7 +151,7 @@
 {
   validator.load(configFile);
 
-  InterestSigner signer(m_keyChain);
+  security::InterestSigner signer(m_keyChain);
   Interest i1("/hello/world");
   signer.makeSignedInterest(i1);
   size_t nValidated = 0, nFailed = 0;
@@ -179,7 +175,7 @@
 {
   validator.load(configFile);
 
-  InterestSigner signer(m_keyChain);
+  security::InterestSigner signer(m_keyChain);
   auto i1 = signer.makeCommandInterest("/hello/world");
   size_t nValidated = 0, nFailed = 0;
 
@@ -200,6 +196,4 @@
 BOOST_AUTO_TEST_SUITE_END() // TestValidatorConfig
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/validator-config/checker.t.cpp b/tests/unit/security/validator-config/checker.t.cpp
index 1170156..6c61085 100644
--- a/tests/unit/security/validator-config/checker.t.cpp
+++ b/tests/unit/security/validator-config/checker.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2021 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -27,14 +27,9 @@
 #include "tests/unit/security/validator-fixture.hpp"
 #include "tests/unit/security/validator-config/common.hpp"
 
-namespace ndn {
-namespace security {
-inline namespace v2 {
-namespace validator_config {
-namespace tests {
+namespace ndn::tests {
 
-using namespace ndn::tests;
-using namespace ndn::security::tests;
+using namespace ndn::security::validator_config;
 
 BOOST_AUTO_TEST_SUITE(Security)
 BOOST_AUTO_TEST_SUITE(ValidatorConfig)
@@ -343,8 +338,4 @@
 BOOST_AUTO_TEST_SUITE_END() // ValidatorConfig
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace validator_config
-} // inline namespace v2
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/validator-config/common.hpp b/tests/unit/security/validator-config/common.hpp
index c4a4fe3..c984cf5 100644
--- a/tests/unit/security/validator-config/common.hpp
+++ b/tests/unit/security/validator-config/common.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2020 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -26,11 +26,9 @@
 
 #include <boost/property_tree/info_parser.hpp>
 
-namespace ndn {
-namespace security {
-inline namespace v2 {
-namespace validator_config {
-namespace tests {
+namespace ndn::tests {
+
+using ndn::security::validator_config::ConfigSection;
 
 inline ConfigSection
 makeSection(const std::string& config)
@@ -41,10 +39,6 @@
   return section;
 }
 
-} // namespace tests
-} // namespace validator_config
-} // inline namespace v2
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
 
 #endif // NDN_CXX_TESTS_UNIT_SECURITY_VALIDATOR_CONFIG_COMMON_HPP
diff --git a/tests/unit/security/validator-config/filter.t.cpp b/tests/unit/security/validator-config/filter.t.cpp
index 42eeceb..a83217b 100644
--- a/tests/unit/security/validator-config/filter.t.cpp
+++ b/tests/unit/security/validator-config/filter.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2021 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -25,14 +25,9 @@
 #include "tests/unit/security/validator-config/common.hpp"
 #include "tests/unit/security/validator-fixture.hpp"
 
-namespace ndn {
-namespace security {
-inline namespace v2 {
-namespace validator_config {
-namespace tests {
+namespace ndn::tests {
 
-using namespace ndn::tests;
-using namespace ndn::security::tests;
+using namespace ndn::security::validator_config;
 
 BOOST_AUTO_TEST_SUITE(Security)
 BOOST_AUTO_TEST_SUITE(ValidatorConfig)
@@ -198,8 +193,4 @@
 BOOST_AUTO_TEST_SUITE_END() // ValidatorConfig
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace validator_config
-} // inline namespace v2
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/validator-config/name-relation.t.cpp b/tests/unit/security/validator-config/name-relation.t.cpp
index 8879212..c81a092 100644
--- a/tests/unit/security/validator-config/name-relation.t.cpp
+++ b/tests/unit/security/validator-config/name-relation.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2020 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -25,11 +25,9 @@
 
 #include <boost/lexical_cast.hpp>
 
-namespace ndn {
-namespace security {
-inline namespace v2 {
-namespace validator_config {
-namespace tests {
+namespace ndn::tests {
+
+using namespace ndn::security::validator_config;
 
 BOOST_AUTO_TEST_SUITE(Security)
 BOOST_AUTO_TEST_SUITE(ValidatorConfig)
@@ -49,7 +47,7 @@
   BOOST_CHECK_EQUAL(getNameRelationFromString("equal"), NameRelation::EQUAL);
   BOOST_CHECK_EQUAL(getNameRelationFromString("is-prefix-of"), NameRelation::IS_PREFIX_OF);
   BOOST_CHECK_EQUAL(getNameRelationFromString("is-strict-prefix-of"), NameRelation::IS_STRICT_PREFIX_OF);
-  BOOST_CHECK_THROW(getNameRelationFromString("unknown"), validator_config::Error);
+  BOOST_CHECK_THROW(getNameRelationFromString("unknown"), Error);
 }
 
 BOOST_AUTO_TEST_CASE(CheckRelation)
@@ -70,8 +68,4 @@
 BOOST_AUTO_TEST_SUITE_END() // ValidatorConfig
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace validator_config
-} // inline namespace v2
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/validator-config/rule.t.cpp b/tests/unit/security/validator-config/rule.t.cpp
index 4871521..ea0b4b7 100644
--- a/tests/unit/security/validator-config/rule.t.cpp
+++ b/tests/unit/security/validator-config/rule.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2021 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -27,14 +27,9 @@
 
 #include <boost/mpl/vector_c.hpp>
 
-namespace ndn {
-namespace security {
-inline namespace v2 {
-namespace validator_config {
-namespace tests {
+namespace ndn::tests {
 
-using namespace ndn::tests;
-using namespace ndn::security::tests;
+using namespace ndn::security::validator_config;
 
 BOOST_AUTO_TEST_SUITE(Security)
 BOOST_AUTO_TEST_SUITE(ValidatorConfig)
@@ -54,7 +49,7 @@
   const std::string ruleId = "rule-id";
   Rule rule;
   Name pktName;
-  shared_ptr<ValidationState> state;
+  shared_ptr<security::ValidationState> state;
 };
 
 using PktTypes = boost::mpl::vector<DataPkt, InterestV02Pkt, InterestV03Pkt>;
@@ -211,8 +206,4 @@
 BOOST_AUTO_TEST_SUITE_END() // ValidatorConfig
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace validator_config
-} // inline namespace v2
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/validator-fixture.cpp b/tests/unit/security/validator-fixture.cpp
index 0e780b4..41497bf 100644
--- a/tests/unit/security/validator-fixture.cpp
+++ b/tests/unit/security/validator-fixture.cpp
@@ -22,11 +22,11 @@
 #include "tests/unit/security/validator-fixture.hpp"
 
 #include "ndn-cxx/security/additional-description.hpp"
+#include "ndn-cxx/util/signal/scoped-connection.hpp"
 
-namespace ndn {
-namespace security {
-inline namespace v2 {
-namespace tests {
+namespace ndn::tests {
+
+using namespace ndn::security;
 
 ValidatorFixtureBase::ValidatorFixtureBase()
 {
@@ -45,7 +45,7 @@
 void
 ValidatorFixtureBase::mockNetworkOperations()
 {
-  util::signal::ScopedConnection conn = face.onSendInterest.connect([this] (const Interest& interest) {
+  signal::ScopedConnection conn = face.onSendInterest.connect([this] (const Interest& interest) {
     if (processInterest) {
       m_io.post([=] { processInterest(interest); });
     }
@@ -102,7 +102,4 @@
   return interest.getName();
 }
 
-} // namespace tests
-} // inline namespace v2
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/validator-fixture.hpp b/tests/unit/security/validator-fixture.hpp
index 39e4ed3..6d69a1e 100644
--- a/tests/unit/security/validator-fixture.hpp
+++ b/tests/unit/security/validator-fixture.hpp
@@ -31,12 +31,13 @@
 
 #include <boost/lexical_cast.hpp>
 
-namespace ndn {
-namespace security {
-inline namespace v2 {
-namespace tests {
+namespace ndn::tests {
 
-class ValidatorFixtureBase : public ndn::tests::IoKeyChainFixture
+using ndn::security::Certificate;
+using ndn::security::Identity;
+using ndn::security::ValidationError;
+
+class ValidatorFixtureBase : public IoKeyChainFixture
 {
 protected:
   ValidatorFixtureBase();
@@ -63,9 +64,9 @@
   addSubCertificate(const Name& subIdentityName, const Identity& issuer);
 
 protected:
-  util::DummyClientFace face{m_io, {true, true}};
+  DummyClientFace face{m_io, {true, true}};
   std::function<void(const Interest&)> processInterest;
-  CertificateCache cache{100_days};
+  security::CertificateCache cache{100_days};
   ValidationError lastError{ValidationError::NO_ERROR};
 
 private:
@@ -73,7 +74,7 @@
   static constexpr int s_mockTimes{200};
 };
 
-template<class ValidationPolicyT, class CertificateFetcherT = CertificateFetcherFromNetwork>
+template<class ValidationPolicyT, class CertificateFetcherT = security::CertificateFetcherFromNetwork>
 class ValidatorFixture : public ValidatorFixtureBase
 {
 protected:
@@ -109,11 +110,11 @@
   }
 
 protected:
-  Validator validator;
+  security::Validator validator;
   ValidationPolicyT& policy;
 };
 
-template<class ValidationPolicyT, class CertificateFetcherT = CertificateFetcherFromNetwork>
+template<class ValidationPolicyT, class CertificateFetcherT = security::CertificateFetcherFromNetwork>
 class HierarchicalValidatorFixture : public ValidatorFixture<ValidationPolicyT, CertificateFetcherT>
 {
 protected:
@@ -142,7 +143,7 @@
 #define VALIDATE_SUCCESS(packet, message) this->validate(packet, message, true, __LINE__)
 #define VALIDATE_FAILURE(packet, message) this->validate(packet, message, false, __LINE__)
 
-class DummyValidationState : public ValidationState
+class DummyValidationState : public security::ValidationState
 {
 public:
   ~DummyValidationState() override
@@ -190,7 +191,7 @@
     return Data(name);
   }
 
-  static shared_ptr<ValidationState>
+  static shared_ptr<security::ValidationState>
   makeState()
   {
     return make_shared<DummyValidationState>();
@@ -214,11 +215,11 @@
     return Interest(name);
   }
 
-  static shared_ptr<ValidationState>
+  static shared_ptr<security::ValidationState>
   makeState()
   {
     auto state = make_shared<DummyValidationState>();
-    state->setTag(make_shared<SignedInterestFormatTag>(SignedInterestFormat::V02));
+    state->setTag(make_shared<security::SignedInterestFormatTag>(security::SignedInterestFormat::V02));
     return state;
   }
 };
@@ -240,18 +241,15 @@
     return Interest(name);
   }
 
-  static shared_ptr<ValidationState>
+  static shared_ptr<security::ValidationState>
   makeState()
   {
     auto state = make_shared<DummyValidationState>();
-    state->setTag(make_shared<SignedInterestFormatTag>(SignedInterestFormat::V03));
+    state->setTag(make_shared<security::SignedInterestFormatTag>(security::SignedInterestFormat::V03));
     return state;
   }
 };
 
-} // namespace tests
-} // inline namespace v2
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
 
 #endif // NDN_CXX_TESTS_UNIT_SECURITY_VALIDATOR_FIXTURE_HPP
diff --git a/tests/unit/security/validator-null.t.cpp b/tests/unit/security/validator-null.t.cpp
index 5ad9be5..ebae900 100644
--- a/tests/unit/security/validator-null.t.cpp
+++ b/tests/unit/security/validator-null.t.cpp
@@ -24,12 +24,12 @@
 #include "tests/boost-test.hpp"
 #include "tests/key-chain-fixture.hpp"
 
-namespace ndn {
-namespace security {
-namespace tests {
+namespace ndn::tests {
+
+using ndn::security::ValidatorNull;
 
 BOOST_AUTO_TEST_SUITE(Security)
-BOOST_FIXTURE_TEST_SUITE(TestValidatorNull, ndn::tests::KeyChainFixture)
+BOOST_FIXTURE_TEST_SUITE(TestValidatorNull, KeyChainFixture)
 
 BOOST_AUTO_TEST_CASE(ValidateData)
 {
@@ -58,6 +58,4 @@
 BOOST_AUTO_TEST_SUITE_END() // TestValidatorNull
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/validator.t.cpp b/tests/unit/security/validator.t.cpp
index d1b746b..c56db6a 100644
--- a/tests/unit/security/validator.t.cpp
+++ b/tests/unit/security/validator.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2022 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -25,12 +25,9 @@
 #include "tests/test-common.hpp"
 #include "tests/unit/security/validator-fixture.hpp"
 
-namespace ndn {
-namespace security {
-inline namespace v2 {
-namespace tests {
+namespace ndn::tests {
 
-using namespace ndn::tests;
+using namespace ndn::security;
 
 BOOST_AUTO_TEST_SUITE(Security)
 BOOST_FIXTURE_TEST_SUITE(TestValidator, HierarchicalValidatorFixture<ValidationPolicySimpleHierarchy>)
@@ -378,7 +375,4 @@
 BOOST_AUTO_TEST_SUITE_END() // TestValidator
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // inline namespace v2
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/validity-period.t.cpp b/tests/unit/security/validity-period.t.cpp
index dbcd47f..1fbd6b1 100644
--- a/tests/unit/security/validity-period.t.cpp
+++ b/tests/unit/security/validity-period.t.cpp
@@ -27,11 +27,9 @@
 
 #include <boost/lexical_cast.hpp>
 
-namespace ndn {
-namespace security {
-namespace tests {
+namespace ndn::tests {
 
-using namespace ndn::tests;
+using ndn::security::ValidityPeriod;
 
 BOOST_CONCEPT_ASSERT((boost::EqualityComparable<ValidityPeriod>));
 BOOST_CONCEPT_ASSERT((WireEncodable<ValidityPeriod>));
@@ -121,8 +119,8 @@
 
 BOOST_AUTO_TEST_CASE(EncodingDecoding)
 {
-  time::system_clock::TimePoint notBefore = time::getUnixEpoch();
-  time::system_clock::TimePoint notAfter = notBefore + 1_day;
+  time::system_clock::time_point notBefore = time::getUnixEpoch();
+  time::system_clock::time_point notAfter = notBefore + 1_day;
   ValidityPeriod v1(notBefore, notAfter);
   BOOST_CHECK_EQUAL_COLLECTIONS(v1.wireEncode().begin(), v1.wireEncode().end(),
                                 VP1, VP1 + sizeof(VP1));
@@ -206,9 +204,9 @@
 
 BOOST_AUTO_TEST_CASE(Comparison)
 {
-  time::system_clock::TimePoint notBefore = time::getUnixEpoch();
-  time::system_clock::TimePoint notAfter = notBefore + 1_day;
-  time::system_clock::TimePoint notAfter2 = notBefore + 2_days;
+  auto notBefore = time::getUnixEpoch();
+  auto notAfter = notBefore + 1_day;
+  auto notAfter2 = notBefore + 2_days;
 
   ValidityPeriod validity1(notBefore, notAfter);
   ValidityPeriod validity2(notBefore, notAfter);
@@ -221,6 +219,4 @@
 BOOST_AUTO_TEST_SUITE_END() // TestValidityPeriod
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests
diff --git a/tests/unit/security/verification-helpers.t.cpp b/tests/unit/security/verification-helpers.t.cpp
index 83d37da..868333d 100644
--- a/tests/unit/security/verification-helpers.t.cpp
+++ b/tests/unit/security/verification-helpers.t.cpp
@@ -29,11 +29,9 @@
 #include <openssl/opensslv.h>
 #include <boost/mpl/vector.hpp>
 
-namespace ndn {
-namespace security {
-namespace tests {
+namespace ndn::tests {
 
-using namespace ndn::tests;
+using namespace ndn::security;
 
 BOOST_AUTO_TEST_SUITE(Security)
 BOOST_AUTO_TEST_SUITE(TestVerificationHelpers)
@@ -680,6 +678,4 @@
 BOOST_AUTO_TEST_SUITE_END() // TestVerificationHelpers
 BOOST_AUTO_TEST_SUITE_END() // Security
 
-} // namespace tests
-} // namespace security
-} // namespace ndn
+} // namespace ndn::tests