I took a look at this last night, and found the combination of moving stuff around *and* refactoring it at the same time was too hard to review.

So, once the PEP 451 changes for runpy are done, I think it would make more sense to tackle this as at least three patches:

1. Do the refactoring *within* test_runpy to make the helper API a bit cleaner (this should also use types.SimpleNamespace where appropriate rather than a custom alternative)

2. Move the helper API out to a documented test.support.package_helper module without altering the test.support API

3+. Refactor other test modules to use the now shared API (there may be some pkg related functionality to move out of script_helper as well).