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/AngleCandidateBuilderTests.cs

@@ -0,0 +1,155 @@
+using OpenNest.Engine;
+using OpenNest.Engine.Fill;
+using OpenNest.Geometry;
+using OpenNest.Math;
+
+namespace OpenNest.Tests.Fill;
+
+public class AngleCandidateBuilderTests
+{
+    private static Drawing MakeRectDrawing(double w, double h)
+    {
+        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(w, 0)));
+        pgm.Codes.Add(new OpenNest.CNC.LinearMove(new Vector(w, h)));
+        pgm.Codes.Add(new OpenNest.CNC.LinearMove(new Vector(0, h)));
+        pgm.Codes.Add(new OpenNest.CNC.LinearMove(new Vector(0, 0)));
+        return new Drawing("rect", pgm);
+    }
+
+    private static ClassificationResult MakeClassification(double primaryAngle = 0, PartType type = PartType.Irregular)
+        => new ClassificationResult { PrimaryAngle = primaryAngle, Type = type };
+
+    [Fact]
+    public void Build_ReturnsAtLeastTwoAngles()
+    {
+        var builder = new AngleCandidateBuilder();
+        var item = new NestItem { Drawing = MakeRectDrawing(20, 10) };
+        var workArea = new Box(0, 0, 100, 100);
+
+        var angles = builder.Build(item, MakeClassification(), workArea);
+
+        Assert.True(angles.Count >= 2);
+    }
+
+    [Fact]
+    public void Build_RectangleType_NarrowWorkArea_UsesBaseAnglesOnly()
+    {
+        var builder = new AngleCandidateBuilder();
+        var item = new NestItem { Drawing = MakeRectDrawing(20, 10) };
+        var narrowArea = new Box(0, 0, 100, 8); // narrower than part's longest side
+
+        var angles = builder.Build(item, MakeClassification(0, PartType.Rectangle), narrowArea);
+
+        // Rectangle classification always returns exactly 2 angles regardless of work area
+        Assert.Equal(2, angles.Count);
+    }
+
+    [Fact]
+    public void ForceFullSweep_ProducesFullSweep()
+    {
+        var builder = new AngleCandidateBuilder { ForceFullSweep = true };
+        var item = new NestItem { Drawing = MakeRectDrawing(5, 5) };
+        var workArea = new Box(0, 0, 100, 100);
+
+        var angles = builder.Build(item, MakeClassification(), workArea);
+
+        // Full sweep at 5deg steps = ~36 angles (0 to 175), plus base angles
+        Assert.True(angles.Count > 10);
+    }
+
+    [Fact]
+    public void RecordProductive_PrunesSubsequentBuilds()
+    {
+        var builder = new AngleCandidateBuilder { ForceFullSweep = true };
+        var item = new NestItem { Drawing = MakeRectDrawing(20, 10) };
+        var workArea = new Box(0, 0, 100, 8);
+
+        // First build — full sweep
+        var firstAngles = builder.Build(item, MakeClassification(), workArea);
+
+        // Record some as productive
+        var productive = new List<AngleResult>
+        {
+            new AngleResult { AngleDeg = 0, PartCount = 5 },
+            new AngleResult { AngleDeg = 45, PartCount = 3 },
+        };
+        builder.RecordProductive(productive);
+
+        // Second build — should be pruned to known-good + base angles
+        builder.ForceFullSweep = false;
+        var secondAngles = builder.Build(item, MakeClassification(), workArea);
+
+        Assert.True(secondAngles.Count < firstAngles.Count,
+            $"Pruned ({secondAngles.Count}) should be fewer than full ({firstAngles.Count})");
+    }
+
+    [Fact]
+    public void Build_RectanglePart_ReturnsTwoAngles()
+    {
+        var builder = new AngleCandidateBuilder();
+        var item = new NestItem { Drawing = MakeRectDrawing(20, 10) };
+        var workArea = new Box(0, 0, 100, 100);
+        var classification = MakeClassification(0, PartType.Rectangle);
+
+        var angles = builder.Build(item, classification, workArea);
+
+        Assert.Equal(2, angles.Count);
+    }
+
+    [Fact]
+    public void Build_CirclePart_ReturnsOneAngle()
+    {
+        var builder = new AngleCandidateBuilder();
+        var item = new NestItem { Drawing = MakeRectDrawing(10, 10) };
+        var workArea = new Box(0, 0, 100, 100);
+        var classification = MakeClassification(0, PartType.Circle);
+
+        var angles = builder.Build(item, classification, workArea);
+
+        Assert.Single(angles);
+        Assert.Equal(0, angles[0]);
+    }
+
+    [Fact]
+    public void Build_UserConstraints_OverrideRectangleClassification()
+    {
+        var builder = new AngleCandidateBuilder();
+        var item = new NestItem
+        {
+            Drawing = MakeRectDrawing(100, 50),
+            RotationStart = Angle.ToRadians(10),
+            RotationEnd = Angle.ToRadians(90),
+            StepAngle = Angle.ToRadians(10),
+        };
+        var classification = MakeClassification(0, PartType.Rectangle);
+        var workArea = new Box(0, 0, 1000, 500);
+
+        var angles = builder.Build(item, classification, workArea);
+
+        Assert.True(angles.Count > 2,
+            $"User constraints should override rect classification, got {angles.Count} angles");
+    }
+
+    [Fact]
+    public void Build_UserConstraints_StartingAtZero_AreRespected()
+    {
+        var builder = new AngleCandidateBuilder();
+        var item = new NestItem
+        {
+            Drawing = MakeRectDrawing(100, 50),
+            RotationStart = 0,
+            RotationEnd = System.Math.PI,
+            StepAngle = Angle.ToRadians(45),
+        };
+        var classification = MakeClassification(0, PartType.Rectangle);
+        var workArea = new Box(0, 0, 1000, 500);
+
+        var angles = builder.Build(item, classification, workArea);
+
+        // Start=0, End=PI is NOT "no constraints" — it's a real 0-180 range
+        Assert.True(angles.Count > 2,
+            $"0-to-PI constraint should produce multiple angles, got {angles.Count}");
+    }
+}