Context

The GitHub Repository Archival Bot flagged mongodb-labs/mongo-mockup-db (inactive since ~2021). It remains an active test dependency of PyMongo, so we want to keep and actively maintain it. See also PYTHON-6001 - pin mockupdb to released version instead of master branch.

Problem

The repo has no functioning CI, and the setup.py classifiers stop at Python 3.8.

Definition of done

• Add GitHub Actions CI: test matrix over supported CPythons (3.9–3.15 + pypy3), run the repo's own tests/ suite (tox.ini exists as a starting point).
• Update classifiers and get CI passing.
• Cut a 1.9 release to PyPI so PyMongo can move off the 2021-era 1.8.1 pin (PYTHON-6001 pinned to the release because master was unbuildable/untestable).
• Add a README note that the repo is actively consumed by PyMongo's test suite.

Pitfalls

There may be some changes needed in the repo to directly support pymongo 4.x and cpython 3.10+, but are not likely
given that we test from the newer pymongo and CPython downstream.