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/Geometry/ContourClassificationTests.cs

@@ -0,0 +1,157 @@
+using OpenNest.Converters;
+using OpenNest.Geometry;
+
+namespace OpenNest.Tests.Geometry;
+
+public class ContourClassificationTests
+{
+    private static Shape MakeRectShape(double x, double y, double w, double h)
+    {
+        var shape = new Shape();
+        shape.Entities.Add(new Line(new Vector(x, y), new Vector(x + w, y)));
+        shape.Entities.Add(new Line(new Vector(x + w, y), new Vector(x + w, y + h)));
+        shape.Entities.Add(new Line(new Vector(x + w, y + h), new Vector(x, y + h)));
+        shape.Entities.Add(new Line(new Vector(x, y + h), new Vector(x, y)));
+        return shape;
+    }
+
+    private static Shape MakeCircleShape(double cx, double cy, double r)
+    {
+        var shape = new Shape();
+        shape.Entities.Add(new Circle(new Vector(cx, cy), r));
+        return shape;
+    }
+
+    private static Shape MakeEtchShape()
+    {
+        var etchLayer = new Layer("ETCH");
+        var shape = new Shape();
+        shape.Entities.Add(new Line(new Vector(10, 10), new Vector(50, 10)) { Layer = etchLayer });
+        return shape;
+    }
+
+    [Fact]
+    public void Classify_identifies_largest_shape_as_perimeter()
+    {
+        var shapes = new List<Shape>
+        {
+            MakeCircleShape(25, 25, 5),
+            MakeRectShape(0, 0, 100, 50),
+            MakeCircleShape(75, 25, 5),
+        };
+
+        var contours = ContourInfo.Classify(shapes);
+
+        Assert.Equal(3, contours.Count);
+        Assert.Single(contours, c => c.Type == ContourClassification.Perimeter);
+        var perimeter = contours.First(c => c.Type == ContourClassification.Perimeter);
+        Assert.Same(shapes[1], perimeter.Shape);
+    }
+
+    [Fact]
+    public void Classify_identifies_closed_non_perimeter_as_holes()
+    {
+        var shapes = new List<Shape>
+        {
+            MakeCircleShape(25, 25, 5),
+            MakeRectShape(0, 0, 100, 50),
+            MakeCircleShape(75, 25, 5),
+        };
+
+        var contours = ContourInfo.Classify(shapes);
+
+        var holes = contours.Where(c => c.Type == ContourClassification.Hole).ToList();
+        Assert.Equal(2, holes.Count);
+    }
+
+    [Fact]
+    public void Classify_identifies_etch_layer_shapes()
+    {
+        var shapes = new List<Shape>
+        {
+            MakeRectShape(0, 0, 100, 50),
+            MakeEtchShape(),
+        };
+
+        var contours = ContourInfo.Classify(shapes);
+
+        Assert.Single(contours, c => c.Type == ContourClassification.Etch);
+    }
+
+    [Fact]
+    public void Classify_identifies_open_shapes()
+    {
+        var openShape = new Shape();
+        openShape.Entities.Add(new Line(new Vector(0, 0), new Vector(10, 0)));
+        openShape.Entities.Add(new Line(new Vector(10, 0), new Vector(10, 5)));
+        // Not closed — doesn't return to (0,0)
+
+        var shapes = new List<Shape>
+        {
+            MakeRectShape(0, 0, 100, 50),
+            openShape,
+        };
+
+        var contours = ContourInfo.Classify(shapes);
+
+        Assert.Single(contours, c => c.Type == ContourClassification.Open);
+    }
+
+    [Fact]
+    public void Classify_orders_holes_first_perimeter_last()
+    {
+        var shapes = new List<Shape>
+        {
+            MakeRectShape(0, 0, 100, 50),
+            MakeCircleShape(25, 25, 5),
+        };
+
+        var contours = ContourInfo.Classify(shapes);
+
+        Assert.Equal(ContourClassification.Hole, contours[0].Type);
+        Assert.Equal(ContourClassification.Perimeter, contours[^1].Type);
+    }
+
+    [Fact]
+    public void Classify_labels_holes_sequentially()
+    {
+        var shapes = new List<Shape>
+        {
+            MakeRectShape(0, 0, 100, 50),
+            MakeCircleShape(25, 25, 5),
+            MakeCircleShape(75, 25, 5),
+        };
+
+        var contours = ContourInfo.Classify(shapes);
+
+        var holes = contours.Where(c => c.Type == ContourClassification.Hole).ToList();
+        Assert.Equal("Hole 1", holes[0].Label);
+        Assert.Equal("Hole 2", holes[1].Label);
+    }
+
+    [Fact]
+    public void Classify_single_shape_is_perimeter()
+    {
+        var shapes = new List<Shape> { MakeRectShape(0, 0, 50, 30) };
+
+        var contours = ContourInfo.Classify(shapes);
+
+        Assert.Single(contours);
+        Assert.Equal(ContourClassification.Perimeter, contours[0].Type);
+        Assert.Equal("Perimeter", contours[0].Label);
+    }
+
+    [Fact]
+    public void Reverse_changes_direction_label()
+    {
+        var shape = MakeRectShape(0, 0, 100, 50);
+        var contours = ContourInfo.Classify(new List<Shape> { shape });
+        var contour = contours[0];
+
+        var originalDirection = contour.DirectionLabel;
+        contour.Reverse();
+        var newDirection = contour.DirectionLabel;
+
+        Assert.NotEqual(originalDirection, newDirection);
+    }
+}