We have tests in value_serialization_test.cpp, that cover Value serialization for sorter, and value serialization into key string. There are some missing types of values. We should increase the coverage by investigating missing types and adding tests for all of them. 

An potential idea for implementing from Mihai: You can imagine having a static map from type tag to testFn, and asserting that, for each type, our map has a testFn for that type tag.