PDF Gen - Update tests for the JSONParser Class (exclude rendering methods)

This is for CI CD work.
Update all unit tests for functionalities excluding rendering ones for the JSONParser Class.

Note: you may need to create many mock schemas for testing to include all scenarios (nested, multi-layer nested, different types)

**TODOs**
- [ ] Figure out all required unit tests
- [ ] Add/Update required tests
- [ ] Run `make test` to make sure all the unit tests work as expected