miroir/notes/bf-59oct.md

bf-59oct — Map each inline Mode A test → grandparent bf-30m2j acceptance criteria

Coverage-map bead. Parent umbrella bf-1zn8a, grandparent bf-30m2j. Step 2 of the coverage investigation; builds on the empirical test-run evidence in sibling bf-qvrmh (which re-confirmed the three tests execute + pass).

This note is the crisp, decisive, per-test assertion-cited coverage map: for each of grandparent bf-30m2j's five acceptance criteria, which of the three inline tests covers it (with the specific assertion + file:line), and where the genuine gap is. The point is to prove the disabled acceptance_4's criteria are already covered inline so later siblings attack the narrow gap instead of rewriting a redundant test.

Test inventory (crates/miroir-core/src/anti_entropy.rs, mod tests_mode_a_acceptance)

Whole module is gated #[cfg(all(test, feature = "peer-discovery"))] @ anti_entropy.rs:1532. All three are plain #[tokio::test] (no #[ignore]), run against the in-memory crate::scatter::MockNodeClient (no docker).

Task shorthand	Actual fn	Location
exactly-one-owner	test_mode_a_three_pods_each_shard_processed_once	anti_entropy.rs:1541
pod-reassignment	test_mode_a_pod_reassignment	anti_entropy.rs:1665
partitioning-wiring	test_mode_a_anti_entropy_partitioning	anti_entropy.rs:1761

All three exercise the current API, not the removed with_mode_a_scaling: ModeACoordinator::new + PeerDiscovery::new + PeerSet::new + set_peer_set_for_test (mode_a_coordinator.rs:306) + with_mode_a (anti_entropy.rs:199). Assertions query ModeACoordinator::owns_shard (mode_a_coordinator.rs:151) → owner_for_shard (:123, top-1 by score) → rendezvous_score (:112) = XxHash64(shard_id || "||" || peer_id) — i.e. exactly top1_by_score(hash(s ‖ pid)) from plan §14.5 (plan.md:3520).

Coverage map (grandparent bf-30m2j criteria 1-5)

Criterion 1 — Rewrite/reinstate acceptance_4 using current ModeACoordinator/peer_discovery API (not removed with_mode_a_scaling) — [COVERED]

The criterion's substance ("exercise the current API, not the deleted with_mode_a_scaling") is satisfied by all three tests. No with_mode_a_scaling symbol exists in the tree (only with_mode_a @ anti_entropy.rs:199):

• partitioning-wiring — ModeACoordinator::new @ anti_entropy.rs:1768; with_mode_a(coordinator) @ anti_entropy.rs:1790.
• exactly-one-owner — ModeACoordinator::new @ anti_entropy.rs:1548/1555/1562; with_mode_a(coordinator_{1,2,3}) @ anti_entropy.rs:1581/1584/1587.
• pod-reassignment — ModeACoordinator::new @ anti_entropy.rs:1672/1679/1686.

The "API drift" the parent cites is already resolved in-tree; any rewrite of acceptance_4 would duplicate this. (The literal act of deleting the dead acceptance_4 is a cleanup, see criterion 5.)

Criterion 2 — Each shard owned by EXACTLY ONE pod (no double-ownership, no orphan), matching top1_by_score(hash(shard_id ‖ pod_id)) — [COVERED by exactly-one-owner: anti_entropy.rs:1622-1635]

• No double-ownership: per-shard assert_eq!(owner_count, 1, …) @ anti_entropy.rs:1622-1626 (counts how many of the 3 pods return owns_shard == true for each shard).
• No orphan: assert_eq!(total_owned, 64, …) @ anti_entropy.rs:1631-1635 (sum of pod1/pod2/pod3 shard counts == 64).
• Even distribution (supplementary): min_owned >= 15, max_owned <= 25 @ anti_entropy.rs:1649-1658.
• Hash match: owns_shard resolves through owner_for_shard (top-1) + rendezvous_score = XxHash64(shard_id ‖ peer_id) (mode_a_coordinator.rs:112-145), the exact top1_by_score(hash(s ‖ pid)) of plan §14.5.

Reinforced by pod-reassignment @ anti_entropy.rs:1733-1737 (owner_count == 1 on pod-3's former shards) and :1751-1755 (total_owned == 64).

Criterion 3 — Ownership redistributes (minimal reshuffling) when peer set changes size — [COVERED for the core; "minimal reshuffling" sub-clause is a narrow GAP]

Core assertion covered by pod-reassignment: anti_entropy.rs:1714-1755:

• Peer set shrinks 3→2: PeerSet::new(["pod-1","pod-2"]) + set_peer_set_for_test @ anti_entropy.rs:1714-1721.
• Redistribution asserted: every shard pod-3 previously owned (captured @ :1705-1711) is now owned by exactly one of pod-1/pod-2 — assert_eq!(owner_count, 1) @ anti_entropy.rs:1733-1737.
• Full coverage preserved: assert_eq!(total_owned, 64, …) @ anti_entropy.rs:1751-1755.

Narrow GAP (the "minimal reshuffling" sub-clause): the test records only pod-3's initial shards (:1705-1711) and re-checks only those. It never records pod-1/pod-2's initial shards and asserts they are unchanged after the resize. A buggy impl that reshuffled all shards on every peer-set change — while still preserving exactly-one-owner + full coverage — would pass. This is parent bf-1zn8a's gap (a): survivor-stability / minimal-reshuffling un-pinned for the Mode A background-work ownership path. (Also no 3→4 scale-up case exists — gap (b).)

So: the literal criterion-3 head ("ownership redistributes when peer set changes size") = COVERED; the parenthetical "minimal reshuffling" qualifier = GAP.

Criterion 4 — Test runs in default cargo test without --ignored or docker — [GAP for "default cargo test"; sub-parts covered]

• No #[ignore]: ✓ — plain #[tokio::test] @ anti_entropy.rs:1540/1664/1760.
• No docker: ✓ — in-memory MockNodeClient @ anti_entropy.rs:1577/1787; synthetic peer set via set_peer_set_for_test (mode_a_coordinator.rs:306), no SRV/DNS.
• "Default cargo test": GAP. The module is #[cfg(all(test, feature = "peer-discovery"))] @ anti_entropy.rs:1532, and peer-discovery is a non-default feature (default = [] @ crates/miroir-core/Cargo.toml:67; peer-discovery = ["trust-dns-resolver"] @ :71). Plain cargo test -p miroir-core mode_a compiles 0 of these tests (confirmed empirically by sibling bf-qvrmh, RUN 1). They execute + pass only under cargo test -p miroir-core --features peer-discovery or make test (--all-features, Makefile:8).

⇒ This is the genuine remaining gap the later siblings should resolve. It is not "rewrite acceptance_4" — it is "make the Mode A partitioning tests discoverable/runnable in default cargo test" (e.g. move the module off the peer-discovery gate; the coordinator only needs set_peer_set_for_test, which already avoids SRV). This is the real narrow gap, per bf-1zn8a recommendation #5.

Criterion 5 — Update/remove stale comment at crates/miroir-core/tests/p13_8_anti_entropy.rs:240-244 — [orthogonal action item, NOT a coverage item]

The inline tests live in src/anti_entropy.rs, not in the tests/p13_8_anti_entropy.rs file. The stale comment @ p13_8_anti_entropy.rs:241-244 still claims the disabled acceptance_4_mode_a_shard_partitioning "uses an old API (with_mode_a_scaling)" and "requires the peer-discovery feature and ModeACoordinator" — now misleading since the live replacement exists at anti_entropy.rs:1532-1798. It cannot be "covered" by the inline suite; it is a standalone ~4-line edit (point at the inline module, drop the dead acceptance_4 reference). Track as its own action under bf-1zn8a recommendation #4 — not marked [GAP] against the inline tests.

Verdict matrix

#	Criterion	Verdict	Covering test : line	Key assertion
1	Current API (not with_mode_a_scaling)	[COVERED]	partitioning-wiring :1790; exactly-one-owner :1581-1587; pod-reassignment :1672-1686	with_mode_a / ModeACoordinator::new
2	Exactly-one owner, no double/orphan, top1_by_score(hash(s‖pid))	[COVERED]	exactly-one-owner :1622-1635	owner_count == 1, total_owned == 64
3	Redistribution on peer-set change (minimal reshuffling)	[COVERED] core / [GAP] minimal-reshuffle	pod-reassignment :1714-1755	owner_count == 1 @ :1733, total_owned == 64 @ 1751
4	Runs in default cargo test, no --ignored/docker	[GAP] (default cargo test); sub-parts ✓	—	gated #[cfg(… feature = "peer-discovery")] @ anti_entropy.rs:1532, default = [] Cargo.toml:67
5	Update stale comment p13_8:240-244	orthogonal action item	—	inline tests are in src/, not the tests/ file

Bottom line

• Criteria 1, 2: fully covered inline.
• Criterion 3: core covered inline; the minimal-reshuffling / survivor-stability sub-clause is the genuine narrow gap (a) — the thing a follow-on sibling should add (record pod-1/pod-2 initial shards, assert unchanged after resize).
• Criterion 4: the default-cargo-test requirement is the other genuine gap — the suite is feature-gated behind non-default peer-discovery. Fixing discoverability (not rewriting a test) is the sibling work.
• Criterion 5: orthogonal cleanup edit, not a coverage item.

The disabled acceptance_4 is redundant — do not rewrite it. Direct later siblings at gaps (a) survivor-stability, (b) 3→4 scale-up, (c) pinned hash-vector, (4) default-feature discoverability, and the criterion-5 comment edit.

Cross-refs

• notes/bf-qvrmh.md — empirical "do the three tests run?" foundation (RUN 1-4).
• notes/bf-1zn8a.md — parent umbrella; full Step 2 map + gaps (a)/(b)/(c).