diff --git a/tests/unit/security/certificate-cache.t.cpp b/tests/unit/security/certificate-cache.t.cpp
index 8c715eb..51aa72b 100644
--- a/tests/unit/security/certificate-cache.t.cpp
+++ b/tests/unit/security/certificate-cache.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).
  *
@@ -43,7 +43,7 @@
   }
 
   void
-  checkFindByInterest(const Name& name, bool canBePrefix, optional<Certificate> expected) const
+  checkFindByInterest(const Name& name, bool canBePrefix, std::optional<Certificate> expected) const
   {
     Interest interest(name);
     interest.setCanBePrefix(canBePrefix);
@@ -95,10 +95,10 @@
   checkFindByInterest(cert.getIdentity(), true, cert);
   checkFindByInterest(cert.getKeyName(), true, cert);
   checkFindByInterest(cert.getName(), false, cert);
-  checkFindByInterest(Name(cert.getName()).appendVersion(), true, nullopt);
+  checkFindByInterest(Name(cert.getName()).appendVersion(), true, std::nullopt);
 
   advanceClocks(12_s);
-  checkFindByInterest(cert.getIdentity(), true, nullopt);
+  checkFindByInterest(cert.getIdentity(), true, std::nullopt);
 }
 
 BOOST_AUTO_TEST_SUITE_END() // TestCertificateCache
diff --git a/tests/unit/security/certificate.t.cpp b/tests/unit/security/certificate.t.cpp
index f113ca9..37243d6 100644
--- a/tests/unit/security/certificate.t.cpp
+++ b/tests/unit/security/certificate.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).
  *
@@ -366,7 +366,7 @@
   sigInfo.removeCustomTlv(tlv::AdditionalDescription);
   sigInfo.addCustomTlv(makeStringBlock(tlv::ValidityPeriod, "malformed"));
   sigInfo.setSignatureType(tlv::DigestSha256);
-  sigInfo.setKeyLocator(nullopt);
+  sigInfo.setKeyLocator(std::nullopt);
   Certificate cert6(cert3);
   cert6.setSignatureInfo(sigInfo);
   BOOST_CHECK_EQUAL(boost::lexical_cast<std::string>(cert6), expected6);
diff --git a/tests/unit/security/key-chain.t.cpp b/tests/unit/security/key-chain.t.cpp
index 98a0721..9bd97af 100644
--- a/tests/unit/security/key-chain.t.cpp
+++ b/tests/unit/security/key-chain.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).
  *
@@ -427,7 +427,7 @@
 
   const uint32_t expectedSigType = SignatureTypeTlvValue;
   const bool shouldHaveKeyLocator = true;
-  const optional<KeyLocator> expectedKeyLocator = cert.getName();
+  const std::optional<KeyLocator> expectedKeyLocator = cert.getName();
 
   bool
   verify(const SigningInfo&) const
@@ -504,7 +504,7 @@
 
   const uint32_t expectedSigType = SignatureTypeTlvValue;
   const bool shouldHaveKeyLocator = true;
-  const optional<KeyLocator> expectedKeyLocator = nullopt; // don't check KeyLocator value
+  const std::optional<KeyLocator> expectedKeyLocator = std::nullopt; // don't check KeyLocator value
 
   bool
   verify(const SigningInfo& si) const
@@ -524,12 +524,12 @@
 
   const uint32_t expectedSigType = tlv::DigestSha256;
   const bool shouldHaveKeyLocator = false;
-  const optional<KeyLocator> expectedKeyLocator = nullopt;
+  const std::optional<KeyLocator> expectedKeyLocator = std::nullopt;
 
   bool
   verify(const SigningInfo&) const
   {
-    return verifySignature(this->packet, nullopt);
+    return verifySignature(this->packet, std::nullopt);
   }
 };
 
@@ -591,7 +591,8 @@
   }
 
   void
-  checkKeyLocatorName(const Certificate& cert, const optional<Name>& klName = nullopt) const
+  checkKeyLocatorName(const Certificate& cert,
+                      const std::optional<Name>& klName = std::nullopt) const
   {
     auto kl = cert.getKeyLocator();
     if (!kl.has_value()) {
diff --git a/tests/unit/security/trust-anchor-container.t.cpp b/tests/unit/security/trust-anchor-container.t.cpp
index 19d6867..09825db 100644
--- a/tests/unit/security/trust-anchor-container.t.cpp
+++ b/tests/unit/security/trust-anchor-container.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).
  *
@@ -20,7 +20,6 @@
  */
 
 #include "ndn-cxx/security/trust-anchor-container.hpp"
-#include "ndn-cxx/util/io.hpp"
 
 #include "tests/boost-test.hpp"
 #include "tests/key-chain-fixture.hpp"
@@ -61,7 +60,7 @@
   }
 
   void
-  checkFindByInterest(const Name& name, bool canBePrefix, optional<Certificate> expected) const
+  checkFindByInterest(const Name& name, bool canBePrefix, std::optional<Certificate> expected) const
   {
     Interest interest(name);
     interest.setCanBePrefix(canBePrefix);
@@ -172,7 +171,7 @@
   checkFindByInterest(identity1.getName().getPrefix(-1), true, cert1);
   checkFindByInterest(cert1.getKeyName(), true, cert1);
   checkFindByInterest(cert1.getName(), false, cert1);
-  checkFindByInterest(Name(identity1.getName()).appendVersion(), true, nullopt);
+  checkFindByInterest(Name(identity1.getName()).appendVersion(), true, std::nullopt);
 
   auto makeIdentity1Cert = [=] (const std::string& issuerId) {
     auto key = identity1.getDefaultKey();
diff --git a/tests/unit/security/validation-policy-command-interest.t.cpp b/tests/unit/security/validation-policy-command-interest.t.cpp
index 604c60d..971b509 100644
--- a/tests/unit/security/validation-policy-command-interest.t.cpp
+++ b/tests/unit/security/validation-policy-command-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).
  *
@@ -64,16 +64,16 @@
 {
 protected:
   Interest
-  makeCommandInterest(const Identity& identity, SignedInterestFormat format = SignedInterestFormat::V02)
+  makeCommandInterest(const Identity& id, SignedInterestFormat format = SignedInterestFormat::V02)
   {
-    Name name = identity.getName();
+    Name name = id.getName();
     name.append("CMD");
     switch (format) {
       case SignedInterestFormat::V02:
-        return m_signer.makeCommandInterest(name, signingByIdentity(identity));
+        return m_signer.makeCommandInterest(name, signingByIdentity(id));
       case SignedInterestFormat::V03: {
         Interest interest(name);
-        m_signer.makeSignedInterest(interest, signingByIdentity(identity));
+        m_signer.makeSignedInterest(interest, signingByIdentity(id));
         return interest;
       }
     }
@@ -198,7 +198,7 @@
 {
   auto i1 = makeCommandInterest(identity, SignedInterestFormat::V03);
   auto si = i1.getSignatureInfo().value();
-  si.setTime(nullopt);
+  si.setTime(std::nullopt);
   i1.setSignatureInfo(si);
   VALIDATE_FAILURE(i1, "Should fail (timestamp is missing)");
   BOOST_TEST(lastError.getCode() == ValidationError::POLICY_ERROR);
@@ -218,7 +218,7 @@
 {
   auto i1 = makeCommandInterest(identity, SignedInterestFormat::V03);
   auto si = i1.getSignatureInfo().value();
-  si.setKeyLocator(nullopt);
+  si.setKeyLocator(std::nullopt);
   i1.setSignatureInfo(si);
   VALIDATE_FAILURE(i1, "Should fail (missing KeyLocator)");
   BOOST_TEST(lastError.getCode() == ValidationError::INVALID_KEY_LOCATOR);
diff --git a/tests/unit/security/validator-fixture.hpp b/tests/unit/security/validator-fixture.hpp
index d8d357f..7e1e0b5 100644
--- a/tests/unit/security/validator-fixture.hpp
+++ b/tests/unit/security/validator-fixture.hpp
@@ -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).
  *
@@ -158,7 +158,7 @@
 
 private:
   void
-  verifyOriginalPacket(const optional<Certificate>&) override
+  verifyOriginalPacket(const std::optional<Certificate>&) override
   {
     // do nothing
   }
diff --git a/tests/unit/security/verification-helpers.t.cpp b/tests/unit/security/verification-helpers.t.cpp
index d3434c8..83d37da 100644
--- a/tests/unit/security/verification-helpers.t.cpp
+++ b/tests/unit/security/verification-helpers.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).
  *
@@ -632,21 +632,21 @@
   Interest interestOldFormat(dataset.goodInterestOldFormat);
   Interest badSigInterestOldFormat(dataset.badSigInterestOldFormat);
 
-  BOOST_CHECK(verifySignature(data, nullopt));
-  BOOST_CHECK(verifySignature(interest, nullopt));
-  BOOST_CHECK(verifySignature(interestOldFormat, nullopt));
+  BOOST_CHECK(verifySignature(data, std::nullopt));
+  BOOST_CHECK(verifySignature(interest, std::nullopt));
+  BOOST_CHECK(verifySignature(interestOldFormat, std::nullopt));
 
-  BOOST_CHECK(!verifySignature(badSigData, nullopt));
-  BOOST_CHECK(!verifySignature(badSigInterest, nullopt));
-  BOOST_CHECK(!verifySignature(badSigInterestOldFormat, nullopt));
+  BOOST_CHECK(!verifySignature(badSigData, std::nullopt));
+  BOOST_CHECK(!verifySignature(badSigInterest, std::nullopt));
+  BOOST_CHECK(!verifySignature(badSigInterestOldFormat, std::nullopt));
 
   Data unsignedData("/some/data");
   Interest unsignedInterest1("/some/interest/with/several/name/components");
   Interest unsignedInterest2("/interest-with-one-name-component");
 
-  BOOST_CHECK(!verifySignature(unsignedData, nullopt));
-  BOOST_CHECK(!verifySignature(unsignedInterest1, nullopt));
-  BOOST_CHECK(!verifySignature(unsignedInterest2, nullopt));
+  BOOST_CHECK(!verifySignature(unsignedData, std::nullopt));
+  BOOST_CHECK(!verifySignature(unsignedInterest1, std::nullopt));
+  BOOST_CHECK(!verifySignature(unsignedInterest2, std::nullopt));
 }
 
 const uint8_t sha256DataUnrecognizedElements[] = {
@@ -673,8 +673,8 @@
   Data data(Block{sha256DataUnrecognizedElements});
   Interest interest(Block{sha256InterestUnrecognizedElements});
 
-  BOOST_CHECK(verifySignature(data, nullopt));
-  BOOST_CHECK(verifySignature(interest, nullopt));
+  BOOST_CHECK(verifySignature(data, std::nullopt));
+  BOOST_CHECK(verifySignature(interest, std::nullopt));
 }
 
 BOOST_AUTO_TEST_SUITE_END() // TestVerificationHelpers