The crdt_snapshot tests share three global statics:
- SNAPSHOT_STATE (latest_snapshot, pending_acks, pending_at_seq) — coordination state
- crdt_state::ALL_OPS / VECTOR_CLOCK — op journal + vector clock
Only the per-thread CRDT is thread-local (init_for_test); these other globals
are shared across test threads. Under default cargo test parallelism, two tests
running concurrently interleave their op writes and snapshot generation, so
assertions like assert_eq!(at_seq, 4) fail with at_seq=5 (the other thread's
ops snuck in).
Add a module-level GLOBAL_STATE_LOCK that all 17 affected tests grab at the
top. unwrap_or_else(|e| e.into_inner()) handles the case where a prior test
panicked while holding the lock (poisoned).
Fixes bug 669 — these two tests were the silent killer behind every agent's
script/test failure (see also bug 668, which advanced agents to merge despite
gates_passed=false; that compounded this by sending failing-tests worktrees
to mergemaster).
All 2636 tests now pass under default parallel execution (no --test-threads=1
needed).
Closes#669.
dave