fix(mtconnect): options carry the authored tag definitions (Task 2 follow-up)

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect.Tests/MTConnectDriverOptionsTests.cs

@@ -56,6 +56,47 @@ public sealed class MTConnectDriverOptionsTests
         reconnect.BackoffMultiplier.ShouldBeGreaterThan(1.0);
     }
 
+    /// <summary>
+    ///     <see cref="MTConnectDriverOptions.Tags"/> defaults to an <i>empty</i> collection, never
+    ///     <c>null</c> — a null collection here is an operator-authorable NullReferenceException at
+    ///     deploy, since a driver instance authored with no tags binds this default.
+    /// </summary>
+    [Fact]
+    public void Options_tags_default_to_empty_and_are_never_null()
+    {
+        var o = new MTConnectDriverOptions { AgentUri = "http://agent:5000" };
+
+        o.Tags.ShouldNotBeNull();
+        o.Tags.ShouldBeEmpty();
+    }
+
+    /// <summary>
+    ///     A populated options object carries the authored tag definitions through unchanged —
+    ///     the observation index (Task 8) coerces each present observation to <i>its tag's</i>
+    ///     DriverDataType, so the definitions must reach the driver from the factory config.
+    /// </summary>
+    [Fact]
+    public void Options_round_trip_the_authored_tag_definitions()
+    {
+        var pos = new MTConnectTagDefinition(
+            FullName: "dev1_pos",
+            DriverDataType: ZB.MOM.WW.OtOpcUa.Core.Abstractions.DriverDataType.Float64,
+            MtCategory: "SAMPLE",
+            MtType: "POSITION",
+            Units: "MILLIMETER");
+        var partCount = new MTConnectTagDefinition(
+            FullName: "dev1_partcount",
+            DriverDataType: ZB.MOM.WW.OtOpcUa.Core.Abstractions.DriverDataType.Int64,
+            MtCategory: "EVENT",
+            MtType: "PART_COUNT");
+
+        var o = new MTConnectDriverOptions { AgentUri = "http://agent:5000", Tags = [pos, partCount] };
+
+        o.Tags.Count.ShouldBe(2);
+        o.Tags[0].ShouldBe(pos);
+        o.Tags[1].ShouldBe(partCount);
+    }
+
     /// <summary>MTConnectTagDefinition round-trips its positional fields, including MTConnect metadata.</summary>
     [Fact]
     public void TagDefinition_carries_dataItemId_and_mtconnect_metadata()