build: switch to C++17

Change-Id: I119767c48c085c62556347ba6c11a85e30c32ced
diff --git a/tests/unit/common.t.cpp b/tests/unit/common.t.cpp
index 3297cd4..c4d995f 100644
--- a/tests/unit/common.t.cpp
+++ b/tests/unit/common.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2014-2020, Regents of the University of California
+ * Copyright (c) 2014-2022, Regents of the University of California
  *
  * This file is part of NAC (Name-Based Access Control for NDN).
  * See AUTHORS.md for complete list of NAC authors and contributors.
@@ -21,16 +21,14 @@
 
 #include "tests/boost-test.hpp"
 
-namespace ndn {
-namespace nac {
-namespace tests {
+namespace ndn::nac::tests {
 
 BOOST_AUTO_TEST_SUITE(TestCommon)
 
 BOOST_AUTO_TEST_CASE(Helpers)
 {
   bool hasFailed = false;
-  auto onFailed = [&] (auto...) { hasFailed = true; };
+  auto onFailed = [&] (auto&&...) { hasFailed = true; };
 
   auto kdkPrefix = convertKekNameToKdkPrefix(Name("/access/prefix/NAC/dataset/KEK/id"), onFailed);
 
@@ -62,6 +60,4 @@
 
 BOOST_AUTO_TEST_SUITE_END()
 
-} // namespace tests
-} // namespace nac
-} // namespace ndn
+} // namespace ndn::nac::tests
diff --git a/tests/unit/encryptor.t.cpp b/tests/unit/encryptor.t.cpp
index d9bafba..02ae88b 100644
--- a/tests/unit/encryptor.t.cpp
+++ b/tests/unit/encryptor.t.cpp
@@ -23,10 +23,12 @@
 #include "tests/io-key-chain-fixture.hpp"
 #include "tests/unit/static-data.hpp"
 
-#include <iostream>
+#include <ndn-cxx/security/signing-helpers.hpp>
 #include <ndn-cxx/util/dummy-client-face.hpp>
 #include <ndn-cxx/util/string-helper.hpp>
 
+#include <iostream>
+
 namespace ndn {
 namespace nac {
 namespace tests {