Added reproduction for akkadotnet#512

src/Akka.Cluster.Hosting.Tests/DDataOptionsSpecs.cs

@@ -0,0 +1,59 @@
+using System.Threading.Tasks;
+using Akka.Actor;
+using Akka.Cluster.Sharding;
+using Akka.Hosting;
+using Microsoft.Extensions.DependencyInjection;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace Akka.Cluster.Hosting.Tests;
+
+public class DDataOptionsSpecs
+{
+    public DDataOptionsSpecs(ITestOutputHelper output)
+    {
+        Output = output;
+    }
+
+    public ITestOutputHelper Output { get; }
+
+    public static readonly TheoryData<DDataOptions> DDataOptionsTypes = new TheoryData<DDataOptions>()
+    {
+        new DDataOptions() // empty
+        {
+            Durable = new DurableOptions()
+            {
+                Keys = []
+            }
+        },
+        new DDataOptions() // null
+        {
+            Durable = new DurableOptions()
+            {
+                Keys = null
+            }
+        },
+    };
+
+    /// <summary>
+    /// Reproduction for https://github.com/akkadotnet/Akka.Hosting/issues/512 
+    /// </summary>
+    [Theory]
+    [MemberData(nameof(DDataOptionsTypes))]
+    public async Task Should_not_emit_durable_keys_when_empty(DDataOptions options)
+    {
+        // arrange
+        using var host = await TestHelper.CreateHost(builder => { builder.WithDistributedData(options); },
+            new ClusterOptions() { Roles = new[] { "my-host" } }, Output);
+
+        var actorSystem = host.Services.GetRequiredService<ActorSystem>();
+
+        // act
+        var config = actorSystem.Settings.Config.GetConfig("akka.cluster.distributed-data");
+
+        // assert
+        Assert.True(config.HasPath("durable.keys"));
+        var keys = config.GetStringList("durable.keys");
+        Assert.Empty(keys);
+    }
+}