feat(otopcua): make FixedTree re-discovery per-pass timeout injectable (follow-up A)

tests/Server/ZB.MOM.WW.OtOpcUa.Runtime.Tests/Drivers/DriverInstanceActorDiscoveryTests.cs

@@ -171,6 +171,32 @@ public sealed class DriverInstanceActorDiscoveryTests : RuntimeActorTestBase
         driver.DiscoverCount.ShouldBe(3);
     }
 
+    /// <summary>
+    ///     The per-pass discovery timeout is injectable via <see cref="DriverInstanceActor.Props"/> so tests
+    ///     can control it without real-time delays. The default constant must be 30 seconds (behaviour-preserving).
+    ///     Wiring is verified by constructing via <c>Props</c> with a custom value and confirming the actor starts
+    ///     and begins discovery normally.
+    /// </summary>
+    [Fact]
+    public void Discovery_timeout_default_constant_is_30s_and_Props_accepts_custom_value()
+    {
+        // The constant must exist and preserve the pre-refactor 30 s literal.
+        DriverInstanceActor.DefaultRediscoverDiscoverTimeout.ShouldBe(TimeSpan.FromSeconds(30));
+
+        // Props must accept the new optional parameter — no throw and actor starts normally.
+        var driver = new DiscoverableStubDriver();
+        var parent = CreateTestProbe();
+        var actor = parent.ChildActorOf(DriverInstanceActor.Props(
+            driver,
+            rediscoverInterval: TimeSpan.FromMilliseconds(20),
+            rediscoverDiscoverTimeout: TimeSpan.FromSeconds(5)));
+
+        actor.Tell(new DriverInstanceActor.InitializeRequested("{}"));
+
+        // Actor starts and discovery publishes — confirms the custom timeout was wired without error.
+        parent.ExpectMsg<DriverInstanceActor.DiscoveredNodesReady>(TimeSpan.FromSeconds(2));
+    }
+
     /// <summary>
     ///     A <see cref="StubDriver"/> that also exposes <see cref="ITagDiscovery"/>. Each <c>DiscoverAsync</c>
     ///     pass is counted; passes 1–2 yield nothing (cache warming), passes 3+ yield a stable 3-node set —