refactor: organize test project into subdirectories by feature area

Move 43 root-level test files into feature-specific subdirectories
mirroring the main codebase structure: Geometry, Fill, BestFit, CutOffs,
CuttingStrategy, Engine, IO. Update namespaces to match folder paths.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

OpenNest.Tests/Fill/ShrinkFillerTests.cs

@@ -0,0 +1,148 @@
+using OpenNest.Engine.Fill;
+using OpenNest.Geometry;
+
+namespace OpenNest.Tests.Fill;
+
+public class ShrinkFillerTests
+{
+    private static Drawing MakeSquareDrawing(double size)
+    {
+        var pgm = new OpenNest.CNC.Program();
+        pgm.Codes.Add(new OpenNest.CNC.RapidMove(new Vector(0, 0)));
+        pgm.Codes.Add(new OpenNest.CNC.LinearMove(new Vector(size, 0)));
+        pgm.Codes.Add(new OpenNest.CNC.LinearMove(new Vector(size, size)));
+        pgm.Codes.Add(new OpenNest.CNC.LinearMove(new Vector(0, size)));
+        pgm.Codes.Add(new OpenNest.CNC.LinearMove(new Vector(0, 0)));
+        return new Drawing("square", pgm);
+    }
+
+    [Fact]
+    public void Shrink_FillsAndReturnsDimension()
+    {
+        var drawing = MakeSquareDrawing(10);
+        var item = new NestItem { Drawing = drawing };
+        var box = new Box(0, 0, 100, 50);
+
+        Func<NestItem, Box, List<Part>> fillFunc = (ni, b) =>
+        {
+            var plate = new Plate(b.Width, b.Length);
+            var engine = new DefaultNestEngine(plate);
+            return engine.Fill(ni, b, null, System.Threading.CancellationToken.None);
+        };
+
+        var result = ShrinkFiller.Shrink(fillFunc, item, box, 1.0, ShrinkAxis.Length);
+
+        Assert.NotNull(result);
+        Assert.True(result.Parts.Count > 0);
+        Assert.True(result.Dimension <= 50, "Dimension should be <= original");
+        Assert.True(result.Dimension > 0);
+    }
+
+    [Fact]
+    public void Shrink_Width_ReducesHorizontally()
+    {
+        var drawing = MakeSquareDrawing(10);
+        var item = new NestItem { Drawing = drawing };
+        var box = new Box(0, 0, 100, 50);
+
+        Func<NestItem, Box, List<Part>> fillFunc = (ni, b) =>
+        {
+            var plate = new Plate(b.Width, b.Length);
+            var engine = new DefaultNestEngine(plate);
+            return engine.Fill(ni, b, null, System.Threading.CancellationToken.None);
+        };
+
+        var result = ShrinkFiller.Shrink(fillFunc, item, box, 1.0, ShrinkAxis.Width);
+
+        Assert.NotNull(result);
+        Assert.True(result.Parts.Count > 0);
+        Assert.True(result.Dimension <= 100);
+    }
+
+    [Fact]
+    public void Shrink_RespectsCancellation()
+    {
+        var cts = new System.Threading.CancellationTokenSource();
+        cts.Cancel();
+
+        var drawing = MakeSquareDrawing(10);
+        var item = new NestItem { Drawing = drawing };
+        var box = new Box(0, 0, 100, 50);
+
+        Func<NestItem, Box, List<Part>> fillFunc = (ni, b) =>
+            new List<Part> { TestHelpers.MakePartAt(0, 0, 10) };
+
+        var result = ShrinkFiller.Shrink(fillFunc, item, box, 1.0,
+            ShrinkAxis.Length, token: cts.Token);
+
+        Assert.NotNull(result);
+        Assert.True(result.Parts.Count > 0);
+    }
+
+    [Fact]
+    public void TrimToCount_Width_KeepsPartsNearestToOrigin()
+    {
+        var parts = new List<Part>
+        {
+            TestHelpers.MakePartAt(0, 0, 5),   // Right = 5
+            TestHelpers.MakePartAt(10, 0, 5),  // Right = 15
+            TestHelpers.MakePartAt(20, 0, 5),  // Right = 25
+            TestHelpers.MakePartAt(30, 0, 5),  // Right = 35
+        };
+
+        var trimmed = ShrinkFiller.TrimToCount(parts, 2, ShrinkAxis.Width);
+
+        Assert.Equal(2, trimmed.Count);
+        Assert.True(trimmed.All(p => p.BoundingBox.Right <= 15));
+    }
+
+    [Fact]
+    public void TrimToCount_Length_KeepsPartsNearestToOrigin()
+    {
+        var parts = new List<Part>
+        {
+            TestHelpers.MakePartAt(0, 0, 5),   // Top = 5
+            TestHelpers.MakePartAt(0, 10, 5),  // Top = 15
+            TestHelpers.MakePartAt(0, 20, 5),  // Top = 25
+            TestHelpers.MakePartAt(0, 30, 5),  // Top = 35
+        };
+
+        var trimmed = ShrinkFiller.TrimToCount(parts, 2, ShrinkAxis.Length);
+
+        Assert.Equal(2, trimmed.Count);
+        Assert.True(trimmed.All(p => p.BoundingBox.Top <= 15));
+    }
+
+    [Fact]
+    public void TrimToCount_ReturnsInput_WhenCountAtOrBelowTarget()
+    {
+        var parts = new List<Part>
+        {
+            TestHelpers.MakePartAt(0, 0, 5),
+            TestHelpers.MakePartAt(10, 0, 5),
+        };
+
+        var same = ShrinkFiller.TrimToCount(parts, 2, ShrinkAxis.Width);
+        Assert.Same(parts, same);
+
+        var fewer = ShrinkFiller.TrimToCount(parts, 5, ShrinkAxis.Width);
+        Assert.Same(parts, fewer);
+    }
+
+    [Fact]
+    public void TrimToCount_DoesNotMutateInput()
+    {
+        var parts = new List<Part>
+        {
+            TestHelpers.MakePartAt(0, 0, 5),
+            TestHelpers.MakePartAt(10, 0, 5),
+            TestHelpers.MakePartAt(20, 0, 5),
+        };
+
+        var originalCount = parts.Count;
+        var trimmed = ShrinkFiller.TrimToCount(parts, 1, ShrinkAxis.Width);
+
+        Assert.Equal(originalCount, parts.Count);
+        Assert.Equal(1, trimmed.Count);
+    }
+}