Many aspects of the library involve calculations that must be verified in various forms. This is not just done once on the implementation stage. Instead, verification tests are run at a variety of testing levels, such as unit tests. These calculations are usually done by hand using a spreadsheet or some other automation such that updates, changes, experiments & derivations can easily be done.
These are found at the following location:
Google Drive - Contains all testing-related files that are not in the code base.