Extract utility functions of CodeChain class

CodeChain is a heavy class. I would like to use some helper functions of the CodeChain class in other test code, but CodeChain has too many functionalities and it is hard to pass it as an argument to other functions.

Locate the CodeChain class and identify the helper functions that other test code needs. Review which helpers depend on the class, then extract the reusable utilities without requiring a CodeChain instance. Done means the test code can use those utilities independently and existing tests still pass.

Written by the indexing model from the issue text.