Yield Injection Guide

Yield injection is test-only infrastructure for forcing cooperative-yield or failure boundaries in resumable state machines. The implementation currently lives under core/mvcc/, but the mechanism is not MVCC semantics.

Key Files

• core/mvcc/yield_points.rs: injector traits and macros.
• core/mvcc/yield_hooks.rs: YieldPointMarker, YieldContext, ProvidesYieldContext.
• core/connection.rs: per-connection injector slots and yield_instance_id_counter.
• core/mvcc/database/mod.rs: commit points and commit cleanup.
• core/mvcc/database/checkpoint_state_machine.rs: checkpoint points.
• core/mvcc/cursor.rs: cursor points.
• core/mvcc/database/tests.rs: fixed test injectors and regression examples.
• testing/concurrent-simulator/yield_injection.rs: simulator injector.

All hooks are behind cfg(any(test, injected_yields)); injected_yields means test_helper or simulator.

Core Model

YieldPoint { ordinal, point_count } identifies one hook in one point family. Families are #[repr(u8)] enums implementing YieldPointMarker; ordinal is source-order self as u8, and point_count comes from EnumCount.