Initial import of the CBDDC codebase with docs and tests. Add a .NET-focused gitignore to keep generated artifacts out of source control.

tests/ZB.MOM.WW.CBDDC.Network.Tests/BullyLeaderElectionServiceTests.cs

@@ -0,0 +1,162 @@
+using ZB.MOM.WW.CBDDC.Core;
+using ZB.MOM.WW.CBDDC.Core.Network;
+using ZB.MOM.WW.CBDDC.Network.Leadership;
+
+namespace ZB.MOM.WW.CBDDC.Network.Tests;
+
+public class BullyLeaderElectionServiceTests
+{
+    private static IDiscoveryService CreateDiscovery(IList<PeerNode> peers)
+    {
+        var discovery = Substitute.For<IDiscoveryService>();
+        discovery.GetActivePeers().Returns(_ => peers);
+        return discovery;
+    }
+
+    private static IPeerNodeConfigurationProvider CreateConfig(string nodeId)
+    {
+        var configProvider = Substitute.For<IPeerNodeConfigurationProvider>();
+        configProvider.GetConfiguration().Returns(new PeerNodeConfiguration { NodeId = nodeId });
+        return configProvider;
+    }
+
+    /// <summary>
+    /// Verifies that a single node elects itself as leader.
+    /// </summary>
+    [Fact]
+    public async Task SingleNode_ShouldBecomeLeader()
+    {
+        var peers = new List<PeerNode>();
+        var electionService = new BullyLeaderElectionService(
+            CreateDiscovery(peers),
+            CreateConfig("node-A"),
+            electionInterval: TimeSpan.FromMilliseconds(100));
+
+        LeadershipChangedEventArgs? lastEvent = null;
+        electionService.LeadershipChanged += (_, e) => lastEvent = e;
+
+        await electionService.Start();
+        await Task.Delay(200);
+
+        electionService.IsCloudGateway.ShouldBeTrue();
+        electionService.CurrentGatewayNodeId.ShouldBe("node-A");
+        lastEvent.ShouldNotBeNull();
+        lastEvent!.IsLocalNodeGateway.ShouldBeTrue();
+        lastEvent.CurrentGatewayNodeId.ShouldBe("node-A");
+
+        await electionService.Stop();
+    }
+
+    /// <summary>
+    /// Verifies that the smallest node ID is elected as leader among LAN peers.
+    /// </summary>
+    [Fact]
+    public async Task MultipleNodes_SmallestNodeIdShouldBeLeader()
+    {
+        var peers = new List<PeerNode>
+        {
+            new("node-B", "192.168.1.2:9000", DateTimeOffset.UtcNow, PeerType.LanDiscovered),
+            new("node-C", "192.168.1.3:9000", DateTimeOffset.UtcNow, PeerType.LanDiscovered)
+        };
+
+        var electionService = new BullyLeaderElectionService(
+            CreateDiscovery(peers),
+            CreateConfig("node-A"),
+            electionInterval: TimeSpan.FromMilliseconds(100));
+
+        await electionService.Start();
+        await Task.Delay(200);
+
+        electionService.IsCloudGateway.ShouldBeTrue();
+        electionService.CurrentGatewayNodeId.ShouldBe("node-A");
+
+        await electionService.Stop();
+    }
+
+    /// <summary>
+    /// Verifies that the local node is not elected when it is not the smallest node ID.
+    /// </summary>
+    [Fact]
+    public async Task LocalNodeNotSmallest_ShouldNotBeLeader()
+    {
+        var peers = new List<PeerNode>
+        {
+            new("node-A", "192.168.1.1:9000", DateTimeOffset.UtcNow, PeerType.LanDiscovered),
+            new("node-B", "192.168.1.2:9000", DateTimeOffset.UtcNow, PeerType.LanDiscovered)
+        };
+
+        var electionService = new BullyLeaderElectionService(
+            CreateDiscovery(peers),
+            CreateConfig("node-C"),
+            electionInterval: TimeSpan.FromMilliseconds(100));
+
+        await electionService.Start();
+        await Task.Delay(200);
+
+        electionService.IsCloudGateway.ShouldBeFalse();
+        electionService.CurrentGatewayNodeId.ShouldBe("node-A");
+
+        await electionService.Stop();
+    }
+
+    /// <summary>
+    /// Verifies that leadership is re-elected when the current leader fails.
+    /// </summary>
+    [Fact]
+    public async Task LeaderFailure_ShouldReelect()
+    {
+        var peers = new List<PeerNode>
+        {
+            new("node-A", "192.168.1.1:9000", DateTimeOffset.UtcNow, PeerType.LanDiscovered)
+        };
+
+        var electionService = new BullyLeaderElectionService(
+            CreateDiscovery(peers),
+            CreateConfig("node-B"),
+            electionInterval: TimeSpan.FromMilliseconds(100));
+
+        var leadershipChanges = new List<LeadershipChangedEventArgs>();
+        electionService.LeadershipChanged += (_, e) => leadershipChanges.Add(e);
+
+        await electionService.Start();
+        await Task.Delay(200);
+
+        electionService.CurrentGatewayNodeId.ShouldBe("node-A");
+
+        peers.Clear();
+        await Task.Delay(200);
+
+        electionService.IsCloudGateway.ShouldBeTrue();
+        electionService.CurrentGatewayNodeId.ShouldBe("node-B");
+        leadershipChanges.ShouldNotBeEmpty();
+        leadershipChanges.Last().IsLocalNodeGateway.ShouldBeTrue();
+        leadershipChanges.Last().CurrentGatewayNodeId.ShouldBe("node-B");
+
+        await electionService.Stop();
+    }
+
+    /// <summary>
+    /// Verifies that cloud peers are excluded from LAN gateway election.
+    /// </summary>
+    [Fact]
+    public async Task CloudPeersExcludedFromElection()
+    {
+        var peers = new List<PeerNode>
+        {
+            new("node-A", "192.168.1.1:9000", DateTimeOffset.UtcNow, PeerType.LanDiscovered),
+            new("cloud-node-Z", "cloud.example.com:9000", DateTimeOffset.UtcNow, PeerType.CloudRemote)
+        };
+
+        var electionService = new BullyLeaderElectionService(
+            CreateDiscovery(peers),
+            CreateConfig("node-B"),
+            electionInterval: TimeSpan.FromMilliseconds(100));
+
+        await electionService.Start();
+        await Task.Delay(200);
+
+        electionService.CurrentGatewayNodeId.ShouldBe("node-A");
+
+        await electionService.Stop();
+    }
+}