A reusable differential-testing toolkit for pqi adapters.

An adapter's test suite calls specs with its Adapter value. The battery runs the same operation on the candidate and on the FFI reference and asserts that the protocol-derived observations match.

The throwaway PostgreSQL container lifecycle is baked into specs, so adapter test suites only need hspec (specs MyAdapter.adapter); they don't have to know about testcontainers at all. The SCRAM-SHA-256 authentication spec is part of the connectdb group and boots its own password-auth container.