diff --git a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.S7.Tests/S7TypeMappingTests.cs b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.S7.Tests/S7TypeMappingTests.cs
new file mode 100644
index 0000000..bcaf395
--- /dev/null
+++ b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.S7.Tests/S7TypeMappingTests.cs
@@ -0,0 +1,173 @@
+using Shouldly;
+using Xunit;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.S7.Tests;
+
+/// <summary>
+///     Unit tests for <see cref="S7Driver.ReinterpretRawValue"/> and
+///     <see cref="S7Driver.BoxValueForWrite"/> — the pure read/write type-reinterpret
+///     helpers factored out of <c>ReadOneAsync</c> / <c>WriteOneAsync</c> so they can be
+///     exercised without a live PLC (Driver.S7-014).
+/// </summary>
+[Trait("Category", "Unit")]
+public sealed class S7TypeMappingTests
+{
+    // ── Helpers ──────────────────────────────────────────────────────────────────────────────
+
+    private static S7TagDefinition Tag(string name, S7DataType dt) =>
+        new(name, "DB1.DBW0", dt);
+
+    private static S7ParsedAddress Addr(S7Size size) =>
+        new(S7Area.DataBlock, DbNumber: 1, size, ByteOffset: 0, BitOffset: 0);
+
+    // ── ReinterpretRawValue — implemented types ───────────────────────────────────────────
+
+    [Fact]
+    public void ReinterpretRawValue_Bool_returns_bool()
+    {
+        var tag = new S7TagDefinition("B", "DB1.DBX0.0", S7DataType.Bool);
+        var addr = new S7ParsedAddress(S7Area.DataBlock, 1, S7Size.Bit, 0, 0);
+        S7Driver.ReinterpretRawValue(tag, addr, true).ShouldBe(true);
+        S7Driver.ReinterpretRawValue(tag, addr, false).ShouldBe(false);
+    }
+
+    [Fact]
+    public void ReinterpretRawValue_Byte_returns_byte()
+    {
+        var tag = new S7TagDefinition("By", "DB1.DBB0", S7DataType.Byte);
+        var addr = Addr(S7Size.Byte);
+        S7Driver.ReinterpretRawValue(tag, addr, (byte)42).ShouldBe((byte)42);
+    }
+
+    [Fact]
+    public void ReinterpretRawValue_UInt16_returns_ushort()
+    {
+        S7Driver.ReinterpretRawValue(Tag("U16", S7DataType.UInt16), Addr(S7Size.Word), (ushort)1000)
+            .ShouldBe((ushort)1000);
+    }
+
+    [Fact]
+    public void ReinterpretRawValue_Int16_reinterprets_ushort_as_signed()
+    {
+        // 0xFFFF as ushort == -1 as short (two's complement reinterpret, not Convert).
+        var result = S7Driver.ReinterpretRawValue(Tag("I16", S7DataType.Int16), Addr(S7Size.Word), (ushort)0xFFFF);
+        result.ShouldBe((short)-1);
+    }
+
+    [Fact]
+    public void ReinterpretRawValue_UInt32_returns_uint()
+    {
+        S7Driver.ReinterpretRawValue(Tag("U32", S7DataType.UInt32), Addr(S7Size.DWord), (uint)70_000u)
+            .ShouldBe(70_000u);
+    }
+
+    [Fact]
+    public void ReinterpretRawValue_Int32_reinterprets_uint_as_signed()
+    {
+        // 0xFFFFFFFF as uint == -1 as int.
+        var result = S7Driver.ReinterpretRawValue(Tag("I32", S7DataType.Int32), Addr(S7Size.DWord), 0xFFFF_FFFFu);
+        result.ShouldBe(-1);
+    }
+
+    [Fact]
+    public void ReinterpretRawValue_Float32_converts_uint_bits_to_float()
+    {
+        float expected = 3.14f;
+        uint bits = BitConverter.SingleToUInt32Bits(expected);
+        var result = S7Driver.ReinterpretRawValue(Tag("F32", S7DataType.Float32), Addr(S7Size.DWord), bits);
+        ((float)result).ShouldBe(expected, tolerance: 1e-6f);
+    }
+
+    // ── ReinterpretRawValue — unsupported types throw NotSupportedException ───────────────
+
+    [Theory]
+    [InlineData(S7DataType.Int64)]
+    [InlineData(S7DataType.UInt64)]
+    [InlineData(S7DataType.Float64)]
+    [InlineData(S7DataType.String)]
+    [InlineData(S7DataType.DateTime)]
+    public void ReinterpretRawValue_unsupported_type_throws_NotSupportedException(S7DataType dt)
+    {
+        Should.Throw<NotSupportedException>(() =>
+            S7Driver.ReinterpretRawValue(Tag("x", dt), Addr(S7Size.DWord), (uint)0));
+    }
+
+    // ── BoxValueForWrite — implemented types ─────────────────────────────────────────────
+
+    [Fact]
+    public void BoxValueForWrite_Bool_converts_value_to_bool()
+    {
+        S7Driver.BoxValueForWrite(S7DataType.Bool, true).ShouldBe(true);
+        S7Driver.BoxValueForWrite(S7DataType.Bool, false).ShouldBe(false);
+        S7Driver.BoxValueForWrite(S7DataType.Bool, 1).ShouldBe(true);
+    }
+
+    [Fact]
+    public void BoxValueForWrite_Byte_converts_to_byte()
+    {
+        S7Driver.BoxValueForWrite(S7DataType.Byte, (byte)200).ShouldBe((byte)200);
+    }
+
+    [Fact]
+    public void BoxValueForWrite_UInt16_converts_to_ushort()
+    {
+        S7Driver.BoxValueForWrite(S7DataType.UInt16, (ushort)1234).ShouldBe((ushort)1234);
+    }
+
+    [Fact]
+    public void BoxValueForWrite_Int16_reinterprets_as_ushort_two_complement()
+    {
+        // -1 as short → 0xFFFF as ushort; S7.Net writes the ushort to the wire.
+        S7Driver.BoxValueForWrite(S7DataType.Int16, (short)-1).ShouldBe((ushort)0xFFFF);
+    }
+
+    [Fact]
+    public void BoxValueForWrite_UInt32_converts_to_uint()
+    {
+        S7Driver.BoxValueForWrite(S7DataType.UInt32, 70_000u).ShouldBe(70_000u);
+    }
+
+    [Fact]
+    public void BoxValueForWrite_Int32_reinterprets_as_uint_two_complement()
+    {
+        // -1 as int → 0xFFFFFFFF as uint.
+        S7Driver.BoxValueForWrite(S7DataType.Int32, -1).ShouldBe(0xFFFF_FFFFu);
+    }
+
+    [Fact]
+    public void BoxValueForWrite_Float32_encodes_as_ieee754_uint()
+    {
+        float f = 3.14f;
+        var expected = BitConverter.SingleToUInt32Bits(f);
+        S7Driver.BoxValueForWrite(S7DataType.Float32, f).ShouldBe(expected);
+    }
+
+    // ── BoxValueForWrite — unsupported types throw NotSupportedException ─────────────────
+
+    [Theory]
+    [InlineData(S7DataType.Int64)]
+    [InlineData(S7DataType.UInt64)]
+    [InlineData(S7DataType.Float64)]
+    [InlineData(S7DataType.String)]
+    [InlineData(S7DataType.DateTime)]
+    public void BoxValueForWrite_unsupported_type_throws_NotSupportedException(S7DataType dt)
+    {
+        Should.Throw<NotSupportedException>(() =>
+            S7Driver.BoxValueForWrite(dt, 0));
+    }
+
+    // ── BoxValueForWrite — overflow paths ────────────────────────────────────────────────
+
+    [Fact]
+    public void BoxValueForWrite_Byte_overflows_for_out_of_range_value()
+    {
+        // Convert.ToByte(256) throws OverflowException.
+        Should.Throw<OverflowException>(() => S7Driver.BoxValueForWrite(S7DataType.Byte, 256));
+    }
+
+    [Fact]
+    public void BoxValueForWrite_UInt16_overflows_for_out_of_range_value()
+    {
+        Should.Throw<OverflowException>(() => S7Driver.BoxValueForWrite(S7DataType.UInt16, 65_536));
+    }
+}