## Summary
This PR adds some snapshot tests for the resolver based on executing
resolutions within a "mock" of the Airflow repo (that is: a folder that
contains a subset of the repo's files, but all empty, and with an
only-partially-complete virtual environment). It's intended to act as a
lightweight integration test, to enable us to test resolutions on a
"real" project without adding a dependency on Airflow itself.
