Motivation

We already record each application's serde/BCS formats as an insta snapshot (via the BcsApplication trait) so that unintended changes to the wire format of operations, messages and events show up as a reviewable diff. The GraphQL schema exposed by an application's service has no equivalent guard: today nothing flags an accidental change to the query/mutation surface that clients depend on.

Proposal

Establish a lightweight, purely conventional pattern (no new trait, no macro) for snapshotting a service's GraphQL schema, and apply it to hex-game as the reference implementation.

Unlike BcsApplication::formats(), which is type-only, building an async-graphql Schema needs owned instances of the roots and a ServiceRuntime — so the natural home is a #[cfg(test)] unit test in service.rs, where ServiceRuntime resolves to MockServiceRuntime. Concretely, for hex-game:

• Extract HexService::schema() and have handle_query delegate to it, so the snapshotted SDL cannot drift from what the service actually serves.
• Add a schema_sdl test: insta::assert_snapshot!(service.schema().sdl()), reusing the existing mock-runtime setup.
• Commit the resulting SDL snapshot.
• Apply the pattern the other GraphQL example services.

Test Plan

• cargo test -p hex-game --bin hex_game_service — both query and the new schema_sdl pass.
• Re-ran schema_sdl against the committed snapshot without INSTA_UPDATE to confirm the SDL is deterministic (the MapView hash-suffixed type names are stable across runs).
• cargo fmt -- --check (pinned nightly) and cargo clippy -p hex-game --tests both clean.

Release Plan

• Nothing to do / These changes follow the usual release cycle.

Links

• reviewer checklist