test: add E2E cluster tests and fix leaf/gateway using warnings

tests/NATS.E2E.Tests/ClusterTests.cs

@@ -0,0 +1,91 @@
+using NATS.Client.Core;
+using NATS.E2E.Tests.Infrastructure;
+
+namespace NATS.E2E.Tests;
+
+[Collection("E2E-Cluster")]
+public class ClusterTests(ClusterFixture fixture)
+{
+    [Fact]
+    public async Task Cluster_MessagePropagatesAcrossNodes()
+    {
+        await using var pub = fixture.CreateClient(0);
+        await using var sub = fixture.CreateClient(1);
+        await pub.ConnectAsync();
+        await sub.ConnectAsync();
+
+        await using var subscription = await sub.SubscribeCoreAsync<string>("e2e.cluster.cross");
+        await sub.PingAsync();
+        await pub.PingAsync();
+
+        await pub.PublishAsync("e2e.cluster.cross", "across-nodes");
+
+        using var cts = new CancellationTokenSource(TimeSpan.FromSeconds(10));
+        var msg = await subscription.Msgs.ReadAsync(cts.Token);
+        msg.Data.ShouldBe("across-nodes");
+    }
+
+    [Fact]
+    public async Task Cluster_LateSubscriberReceivesMessages()
+    {
+        await using var pub = fixture.CreateClient(0);
+        await pub.ConnectAsync();
+
+        await using var sub = fixture.CreateClient(2);
+        await sub.ConnectAsync();
+
+        await using var subscription = await sub.SubscribeCoreAsync<string>("e2e.cluster.late");
+        await sub.PingAsync();
+        await pub.PingAsync();
+
+        await pub.PublishAsync("e2e.cluster.late", "late-join");
+
+        using var cts = new CancellationTokenSource(TimeSpan.FromSeconds(10));
+        var msg = await subscription.Msgs.ReadAsync(cts.Token);
+        msg.Data.ShouldBe("late-join");
+    }
+
+    [Fact]
+    public async Task Cluster_QueueGroupAcrossNodes_DeliversOnce()
+    {
+        await using var pub = fixture.CreateClient(0);
+        await using var sub1 = fixture.CreateClient(1);
+        await using var sub2 = fixture.CreateClient(2);
+        await pub.ConnectAsync();
+        await sub1.ConnectAsync();
+        await sub2.ConnectAsync();
+
+        await using var s1 = await sub1.SubscribeCoreAsync<int>("e2e.cluster.qg", queueGroup: "cq");
+        await using var s2 = await sub2.SubscribeCoreAsync<int>("e2e.cluster.qg", queueGroup: "cq");
+        await sub1.PingAsync();
+        await sub2.PingAsync();
+        await pub.PingAsync();
+
+        using var collectionCts = new CancellationTokenSource(TimeSpan.FromSeconds(15));
+        var count1 = 0;
+        var count2 = 0;
+        var allReceived = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
+
+        async Task Collect(INatsSub<int> sub, Action inc, CancellationToken ct)
+        {
+            await foreach (var _ in sub.Msgs.ReadAllAsync(ct))
+            {
+                inc();
+                if (Volatile.Read(ref count1) + Volatile.Read(ref count2) >= 20)
+                    allReceived.TrySetResult();
+            }
+        }
+
+        _ = Collect(s1, () => Interlocked.Increment(ref count1), collectionCts.Token);
+        _ = Collect(s2, () => Interlocked.Increment(ref count2), collectionCts.Token);
+
+        for (var i = 0; i < 20; i++)
+            await pub.PublishAsync("e2e.cluster.qg", i);
+        await pub.PingAsync();
+
+        // Wait for all 20 messages to arrive via event-driven signaling
+        await allReceived.Task.WaitAsync(collectionCts.Token);
+
+        (count1 + count2).ShouldBe(20);
+    }
+}

tests/NATS.E2E.Tests/GatewayTests.cs

@@ -1,4 +1,3 @@
-using NATS.Client.Core;
 using NATS.E2E.Tests.Infrastructure;
 
 namespace NATS.E2E.Tests;

tests/NATS.E2E.Tests/LeafNodeTests.cs

@@ -1,4 +1,3 @@
-using NATS.Client.Core;
 using NATS.E2E.Tests.Infrastructure;
 
 namespace NATS.E2E.Tests;