Replaces three narrow concurrent_branch_* tests (folded in below) with
one parameterized matrix test covering 11 representative
(op_a, op_b, target_overlap) cells, asserting C1-C6 uniformly:
C1 — both complete (no deadlock; tokio::time::timeout(15s))
C2 — status: both 200 or exactly one clean conflict; never 500
C3 — per-target row count
C4 — per-target row identity (named persons present + absent — catches
the symmetric-swap class that count assertions miss; cubic P2 on
commit 64f2b99 flagged this gap on the round-3 merge race test)
C5 — engine state coherent (subsequent /snapshot consistent)
C6 — post-op /change on main succeeds (engine isn't poisoned)
Cells:
a. Merge × Merge, distinct targets — branch_merge_impl race pin
b. Merge × Merge, same target / distinct sources — merge_exclusive serialization
c. Merge × Merge, same source / distinct targets — fanout
d. Merge × Change, into target — per-(table, branch) queue
e. Merge × BranchCreateFrom, target — interaction with refresh path
f. BranchCreateFrom × BranchCreateFrom, distinct parents — round-1 race pin
g. BranchCreateFrom × BranchDelete, unrelated branches — disjoint state
h. BranchDelete × BranchDelete, distinct branches — concurrent refresh
i. BranchDelete × Change, distinct branch — refresh-side vs writer
j. BranchCreateFrom × Change, on source — fork-while-writing
k. Reopen consistency after concurrent pair — disk-vs-cache drift
Each cell:
- spins up its own tempdir + AppState so failures don't cascade,
- aligns the pair at a tokio::sync::Barrier so both reach the engine
close in time,
- wraps in a 15s deadlock timeout,
- asserts identity via a /read with the `get_person` fixture query
(specific names must be present on the right branch and absent from
the wrong one).
Subsumes:
- concurrent_branch_create_from_distinct_parents_does_not_corrupt_coordinator
(now cell f, with identity assertions added)
- concurrent_branch_merges_distinct_targets_do_not_swap_into_each_other
(now cells a + b + c, with identity assertions; the symmetric-swap
blind spot cubic flagged on commit 64f2b99 is closed)
- concurrent_change_during_branch_merge_preserves_writes
(now cell d)
Those three narrow tests are removed in the next commit so this lands
green standalone.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
ac8594462e