diff --git a/NEW/tests/JdeScoping.ConfigManager.Tests/ViewModels/RegexTransformerViewModelTests.cs b/NEW/tests/JdeScoping.ConfigManager.Tests/ViewModels/RegexTransformerViewModelTests.cs
new file mode 100644
index 0000000..2570639
--- /dev/null
+++ b/NEW/tests/JdeScoping.ConfigManager.Tests/ViewModels/RegexTransformerViewModelTests.cs
@@ -0,0 +1,209 @@
+using JdeScoping.ConfigManager.Models;
+using JdeScoping.ConfigManager.ViewModels.PipelineSteps;
+
+namespace JdeScoping.ConfigManager.Tests.ViewModels;
+
+public class RegexTransformerViewModelTests
+{
+    [Fact]
+    public void Constructor_FromModel_LoadsAllProperties()
+    {
+        // Arrange
+        var model = new TransformerModel
+        {
+            Type = "Regex",
+            ColumnName = "BatchID",
+            Pattern = "^IIS_",
+            Replacement = "",
+            IgnoreCase = true,
+            NonMatchBehavior = NonMatchBehavior.ReturnEmpty
+        };
+
+        // Act
+        var vm = new RegexTransformerViewModel(model, () => { });
+
+        // Assert
+        Assert.Equal("BatchID", vm.ColumnName);
+        Assert.Equal("^IIS_", vm.Pattern);
+        Assert.Equal("", vm.Replacement);
+        Assert.True(vm.IsFindReplaceMode);
+        Assert.True(vm.IgnoreCase);
+        Assert.Equal(NonMatchBehavior.ReturnEmpty, vm.NonMatchBehavior);
+    }
+
+    [Fact]
+    public void Constructor_FromModel_MatchExtractMode_WhenReplacementNull()
+    {
+        // Arrange
+        var model = new TransformerModel
+        {
+            Type = "Regex",
+            ColumnName = "Code",
+            Pattern = @"(\d+)",
+            Replacement = null
+        };
+
+        // Act
+        var vm = new RegexTransformerViewModel(model, () => { });
+
+        // Assert
+        Assert.False(vm.IsFindReplaceMode);
+        Assert.True(vm.IsMatchExtractMode);
+    }
+
+    [Fact]
+    public void ToModel_SerializesCorrectly_FindReplaceMode()
+    {
+        // Arrange
+        var vm = new RegexTransformerViewModel(() => { })
+        {
+            ColumnName = "BatchID",
+            Pattern = "^IIS_",
+            Replacement = "",
+            IsFindReplaceMode = true,
+            IgnoreCase = true,
+            NonMatchBehavior = NonMatchBehavior.KeepOriginal
+        };
+
+        // Act
+        var model = vm.ToModel();
+
+        // Assert
+        Assert.Equal("Regex", model.Type);
+        Assert.Equal("BatchID", model.ColumnName);
+        Assert.Equal("^IIS_", model.Pattern);
+        Assert.Equal("", model.Replacement);
+        Assert.True(model.IgnoreCase);
+        Assert.Equal(NonMatchBehavior.KeepOriginal, model.NonMatchBehavior);
+    }
+
+    [Fact]
+    public void ToModel_SerializesCorrectly_MatchExtractMode()
+    {
+        // Arrange
+        var vm = new RegexTransformerViewModel(() => { })
+        {
+            ColumnName = "Code",
+            Pattern = @"(\d+)",
+            IsFindReplaceMode = false
+        };
+
+        // Act
+        var model = vm.ToModel();
+
+        // Assert
+        Assert.Null(model.Replacement); // null indicates Match & Extract mode
+    }
+
+    [Fact]
+    public void TestPatternCommand_ValidPattern_ShowsResult()
+    {
+        // Arrange
+        var vm = new RegexTransformerViewModel(() => { })
+        {
+            Pattern = "^IIS_",
+            Replacement = "",
+            IsFindReplaceMode = true,
+            TestInput = "IIS_12345"
+        };
+
+        // Act
+        vm.TestPatternCommand.Execute(null);
+
+        // Assert
+        Assert.True(vm.HasTestResult);
+        Assert.False(vm.HasTestError);
+        Assert.Equal("12345", vm.TestResultValue);
+        Assert.Equal("Output", vm.TestResultLabel);
+        Assert.Equal("✓", vm.TestResultIcon);
+    }
+
+    [Fact]
+    public void TestPatternCommand_InvalidPattern_ShowsError()
+    {
+        // Arrange
+        var vm = new RegexTransformerViewModel(() => { })
+        {
+            Pattern = "[invalid(regex",
+            Replacement = "",
+            TestInput = "test"
+        };
+
+        // Act
+        vm.TestPatternCommand.Execute(null);
+
+        // Assert
+        Assert.False(vm.HasTestResult);
+        Assert.True(vm.HasTestError);
+        Assert.NotEmpty(vm.TestErrorMessage);
+    }
+
+    [Fact]
+    public void TestPatternCommand_MatchExtract_NoMatch_ShowsNonMatchBehavior()
+    {
+        // Arrange
+        var vm = new RegexTransformerViewModel(() => { })
+        {
+            Pattern = @"(\d+)",
+            IsFindReplaceMode = false,
+            NonMatchBehavior = NonMatchBehavior.ReturnNull,
+            TestInput = "NoNumbers"
+        };
+
+        // Act
+        vm.TestPatternCommand.Execute(null);
+
+        // Assert
+        Assert.True(vm.HasTestResult);
+        Assert.Equal("No Match", vm.TestResultLabel);
+        Assert.Equal("(null)", vm.TestResultValue);
+    }
+
+    [Fact]
+    public void ModeSwitch_UpdatesPatternHelpText()
+    {
+        // Arrange
+        var vm = new RegexTransformerViewModel(() => { })
+        {
+            IsFindReplaceMode = true
+        };
+        var findReplaceHelp = vm.PatternHelpText;
+
+        // Act
+        vm.IsFindReplaceMode = false;
+        var matchExtractHelp = vm.PatternHelpText;
+
+        // Assert
+        Assert.NotEqual(findReplaceHelp, matchExtractHelp);
+        Assert.Contains("capture group", matchExtractHelp, StringComparison.OrdinalIgnoreCase);
+    }
+
+    [Fact]
+    public void Summary_ShowsColumnAndMode()
+    {
+        // Arrange & Act
+        var vm = new RegexTransformerViewModel(() => { })
+        {
+            ColumnName = "BatchID",
+            IsFindReplaceMode = true
+        };
+
+        // Assert
+        Assert.Contains("BatchID", vm.Summary);
+        Assert.Contains("Replace", vm.Summary);
+    }
+
+    [Fact]
+    public void PropertyChange_NotifiesChanged()
+    {
+        // Arrange
+        var changedCalled = false;
+        var vm = new RegexTransformerViewModel(() => changedCalled = true);
+
+        // Act
+        vm.ColumnName = "NewColumn";
+
+        // Assert
+        Assert.True(changedCalled);
+    }
+}