diff --git a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientAttributeMappingTests.cs b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientAttributeMappingTests.cs
index 700ef4a..3234754 100644
--- a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientAttributeMappingTests.cs
+++ b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientAttributeMappingTests.cs
@@ -10,6 +10,8 @@ public sealed class OpcUaClientAttributeMappingTests
 {
     [Theory]
     [InlineData((uint)DataTypes.Boolean, DriverDataType.Boolean)]
+    [InlineData((uint)DataTypes.SByte, DriverDataType.Int16)]
+    [InlineData((uint)DataTypes.Byte, DriverDataType.UInt16)]
     [InlineData((uint)DataTypes.Int16, DriverDataType.Int16)]
     [InlineData((uint)DataTypes.UInt16, DriverDataType.UInt16)]
     [InlineData((uint)DataTypes.Int32, DriverDataType.Int32)]
@@ -27,12 +29,19 @@ public sealed class OpcUaClientAttributeMappingTests
     }
 
     [Fact]
-    public void MapUpstreamDataType_maps_SByte_and_Byte_to_Int16_since_DriverDataType_lacks_8bit()
+    public void MapUpstreamDataType_maps_SByte_to_Int16_since_DriverDataType_lacks_8bit_signed()
     {
-        // DriverDataType has no 8-bit type; conservative widen to Int16. Documented so a
-        // future Core.Abstractions PR that adds Int8/Byte can find this call site.
+        // SByte (signed 8-bit) has no narrower signed type in DriverDataType; widen to Int16.
         OpcUaClientDriver.MapUpstreamDataType(new NodeId((uint)DataTypes.SByte)).ShouldBe(DriverDataType.Int16);
-        OpcUaClientDriver.MapUpstreamDataType(new NodeId((uint)DataTypes.Byte)).ShouldBe(DriverDataType.Int16);
+    }
+
+    [Fact]
+    public void MapUpstreamDataType_maps_Byte_to_UInt16_not_Int16()
+    {
+        // Driver.OpcUaClient-010: Byte is unsigned 0-255 and must map to the unsigned family
+        // (UInt16), NOT Int16. The old mapping misrepresented type metadata for downstream
+        // clients and range/validation logic keyed off DriverDataType.
+        OpcUaClientDriver.MapUpstreamDataType(new NodeId((uint)DataTypes.Byte)).ShouldBe(DriverDataType.UInt16);
     }
 
     [Fact]