- Start from the schema before migration 011 on SQLite and PostgreSQL, with
npm and Composer metadata cached, and check the rows and stored bytes
survive the migration unchanged
- After the upgrade, check two replicas serve the cached document with
matching ETag and Last-Modified and answer conditional requests with 304
- Change the upstream document and check neither replica answers the old
validators with 304, and both agree on the new ones
- Give the PostgreSQL handler test a database of its own, so it shares no
tables with the database package tests on the same server
