uma::bson is a DOM-style C++ API for reading/writing BSON data. Unlike the MongoDB C++ API, which exposes a read-only interface with a separate interface for creating a BSON representation, this API allows reading/writing on the existing data. The API is designed primarily for serialising/deserialising BSON data to/from streams (files, socket connections, etc.).
cmocka is a unit testing framework for C with mock objects. There are a variety of C unit testing frameworks available supporting different platforms and compilers. Some development requires a lot of different compilers and older versions, which makes it difficult to use unit testing frameworks. The idea of CMocka is that a test application only requires the standard C library and CMocka itself to minimize the conflicts with standard C library headers, especially on a lot of different platforms.