crates/simulation/tests/distribution_properties.rs

@@ -484,3 +484,73 @@ fn large_cluster_registry_converges() {
         result.actual
     );
 }
+
+// ────────────────────────────────────────────────────────────────────────────
+// 10. Three-way partition: cluster splits into 3 groups, heals, converges
+// ────────────────────────────────────────────────────────────────────────────
+
+#[test]
+fn three_way_partition_heals_and_converges() {
+    // Given: 9 nodes split into 3 groups {0,1,2}, {3,4,5}, {6,7,8}.
+    // Each group registers a name during the partition. After healing,
+    // all 9 nodes should converge on all 3 names.
+    let config = DistributionSimConfig {
+        name: "three-way-partition".into(),
+        num_nodes: 9,
+        num_rounds: 140,
+        ticks_per_round: 3,
+        actors_per_node: 0,
+        network_faults: vec![
+            // Partition A vs B
+            NetworkFault::Partition {
+                round: 10,
+                partition: Partition {
+                    side_a: vec![0, 1, 2],
+                    side_b: vec![3, 4, 5, 6, 7, 8],
+                    asymmetric: false,
+                },
+            },
+            // Partition B vs C (stacks with the above: now 3 groups isolated)
+            NetworkFault::Partition {
+                round: 10,
+                partition: Partition {
+                    side_a: vec![3, 4, 5],
+                    side_b: vec![6, 7, 8],
+                    asymmetric: false,
+                },
+            },
+            NetworkFault::Heal { round: 60 },
+        ],
+        action_schedule: vec![
+            (20, SimAction::RegisterName { node_idx: 0, name: "group-a-svc".into() }),
+            (20, SimAction::RegisterName { node_idx: 3, name: "group-b-svc".into() }),
+            (20, SimAction::RegisterName { node_idx: 6, name: "group-c-svc".into() }),
+        ],
+        swim: distribution::swim::probe::SwimConfig {
+            probe_interval: 1,
+            probe_timeout: 3,
+            indirect_probes: 1,
+            // Must exceed partition duration (50 rounds × 3 ticks = 150 ticks)
+            suspicion_timeout: 200,
+            dead_reprobe_interval: 10,
+        },
+        ..DistributionSimConfig::default()
+    };
+
+    let (_trace, nodes) = run_simulation_with_nodes(config);
+
+    let alive_count = nodes.iter().filter(|n| n.is_some()).count();
+    assert_eq!(alive_count, 9, "all 9 nodes should survive the three-way partition");
+
+    // After healing + gossip, all 3 names should be resolvable from every node
+    for (i, node) in nodes.iter().enumerate() {
+        if let Some(node) = node {
+            for name in &["group-a-svc", "group-b-svc", "group-c-svc"] {
+                assert!(
+                    node.resolve_name(name).is_some(),
+                    "node {i} should resolve '{name}' after three-way partition heals"
+                );
+            }
+        }
+    }
+}