Add tests for MetadataBuffer

lib/test/test_main.cpp

@@ -1,10 +1,11 @@
 #include "gtest/gtest.h"
 #include "test_ZmqReceiver.cpp"
 #include "test_H5Writer.cpp"
+#include "test_MetadataBuffer.cpp"
 
 using namespace std;
 
 int main(int argc, char **argv) {
   ::testing::InitGoogleTest(&argc, argv);
   return RUN_ALL_TESTS();
-}
+}