Migrate to C++17 and refactor

Change-Id: I53407266939258990a1c3a9363c3ebe9ea113fd2
diff --git a/tests/unit-tests/protocol-encoders.t.cpp b/tests/unit-tests/protocol-encoders.t.cpp
index 720c10e..a569f0e 100644
--- a/tests/unit-tests/protocol-encoders.t.cpp
+++ b/tests/unit-tests/protocol-encoders.t.cpp
@@ -21,13 +21,13 @@
 #include "detail/challenge-encoder.hpp"
 #include "detail/error-encoder.hpp"
 #include "detail/info-encoder.hpp"
-#include "detail/request-encoder.hpp"
 #include "detail/probe-encoder.hpp"
+#include "detail/request-encoder.hpp"
 #include "detail/ca-configuration.hpp"
+
 #include "test-common.hpp"
 
-namespace ndncert {
-namespace tests {
+namespace ndncert::tests {
 
 BOOST_FIXTURE_TEST_SUITE(TestProtocolEncoding, IdentityManagementTimeFixture)
 
@@ -172,5 +172,4 @@
 
 BOOST_AUTO_TEST_SUITE_END() // TestProtocolEncoding
 
-} // namespace tests
-} // namespace ndncert
+} // namespace ndncert::tests