add encoding unit tests

Change-Id: I319a34a760742e6125e6a28c4ddc23fcf2f29cb3
diff --git a/src/detail/probe-encoder.cpp b/src/detail/probe-encoder.cpp
index 5141ba1..0591501 100644
--- a/src/detail/probe-encoder.cpp
+++ b/src/detail/probe-encoder.cpp
@@ -24,7 +24,7 @@
 namespace ndncert {
 
 Block
-ProbeEncoder::encodeApplicationParameters(std::vector<std::tuple<std::string, std::string>>&& parameters)
+ProbeEncoder::encodeApplicationParameters(const std::vector<std::tuple<std::string, std::string>>& parameters)
 {
   auto content = makeEmptyBlock(ndn::tlv::ApplicationParameters);
   for (size_t i = 0; i < parameters.size(); ++i) {
diff --git a/src/detail/probe-encoder.hpp b/src/detail/probe-encoder.hpp
index 0a991c3..0db8cb9 100644
--- a/src/detail/probe-encoder.hpp
+++ b/src/detail/probe-encoder.hpp
@@ -31,7 +31,7 @@
 public:
   // For Client use
   static Block
-  encodeApplicationParameters(std::vector<std::tuple<std::string, std::string>>&& parameters);
+  encodeApplicationParameters(const std::vector<std::tuple<std::string, std::string>>& parameters);
 
   static void
   decodeDataContent(const Block& block, std::vector<std::pair<Name, int>>& availableNames,