merge dup functions in unit test

now we have sooo many `def _app(...) -> App` and similar functions, merge them will reduce LOT of code.

@dosu give me a full file list and how to fix them.

No files, tests, or entry points are named. Start by inventorying the unit-test files containing duplicate _app(...) and similar helpers, then compare their signatures and behavior. Done means an agreed full file list, a consistent consolidation plan, and unit tests that still pass.

Written by the indexing model from the issue text.