Python: Unit test coverage for core (other modules)

[TaoChenOSU]

Track and ensure that all other modules under core (except workflows) in the GA package achieve 85% unit test coverage. Summarize current status, test shortfalls, and what is needed to meet the 85% requirement. Specify which core modules are below threshold and provide action items for each.

• Area: core (other modules, excluding workflows)
• Goal: ≥85% unit test coverage
• Track current status, gaps, actions and blockers

Add any context on coverage tools, exceptions, or reference documents as needed.

[giles17]

Closing because we've now achieved 90% coverage here: