Package-level declarations

JSON compared as a backend may give it back: objects by field whatever their key order (PostgreSQL JSONB reorders keys), numbers by exact value and scale, so 2.50 is not 2.5 and an integer is not a decimal.

A clock that stands still until a test moves it, so a test decides when leases and reservations expire.

A whole store's contract: the backend gives the config of a store, and the kit opens it through its StoreProvider, as the host does, and runs every port's spec against what the store opens. A port the provider forgets to open, or opens wrong, fails here, where the per-port specs (which a backend's test feeds its own classes) would not see it.