Add OPC UA array element write integration test

tests/ZB.MOM.WW.LmxOpcUa.Tests/Integration/ArrayWriteTests.cs

@@ -0,0 +1,50 @@
+using System.Linq;
+using System.Threading.Tasks;
+using Opc.Ua;
+using Shouldly;
+using Xunit;
+using ZB.MOM.WW.LmxOpcUa.Host.Domain;
+using ZB.MOM.WW.LmxOpcUa.Tests.Helpers;
+
+namespace ZB.MOM.WW.LmxOpcUa.Tests.Integration
+{
+    public class ArrayWriteTests
+    {
+        [Fact]
+        public async Task Write_SingleArrayElement_UpdatesWholeArrayValue()
+        {
+            var fixture = OpcUaServerFixture.WithFakeMxAccessClient();
+            fixture.MxAccessClient!.TagValues["MESReceiver_001.MoveInPartNumbers[]"] = Vtq.Good(
+                Enumerable.Range(0, 50).Select(i => $"PART-{i:00}").ToArray());
+
+            await fixture.InitializeAsync();
+            try
+            {
+                using var client = new OpcUaTestClient();
+                await client.ConnectAsync(fixture.EndpointUrl);
+
+                // Browse path: TestMachine_001 -> MESReceiver -> MoveInPartNumbers
+                var nodeId = client.MakeNodeId("MESReceiver_001.MoveInPartNumbers[]");
+
+                var before = client.Read(nodeId).Value as string[];
+                before.ShouldNotBeNull();
+                before.Length.ShouldBe(50);
+                before[1].ShouldBe("PART-01");
+
+                var status = client.Write(nodeId, new[] { "UPDATED-PART" }, indexRange: "1");
+                StatusCode.IsGood(status).ShouldBe(true);
+
+                var after = client.Read(nodeId).Value as string[];
+                after.ShouldNotBeNull();
+                after.Length.ShouldBe(50);
+                after[0].ShouldBe("PART-00");
+                after[1].ShouldBe("UPDATED-PART");
+                after[2].ShouldBe("PART-02");
+            }
+            finally
+            {
+                await fixture.DisposeAsync();
+            }
+        }
+    }
+}