feat: add NfpSlideStrategy for NFP-based best-fit candidate generation

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

OpenNest.Tests/NfpSlideStrategyTests.cs

@@ -0,0 +1,103 @@
+using OpenNest.CNC;
+using OpenNest.Engine.BestFit;
+using OpenNest.Geometry;
+using OpenNest.Math;
+
+namespace OpenNest.Tests;
+
+public class NfpSlideStrategyTests
+{
+    [Fact]
+    public void GenerateCandidates_ReturnsNonEmpty_ForSquare()
+    {
+        var strategy = new NfpSlideStrategy(0, 1, "0 deg NFP");
+        var drawing = TestHelpers.MakeSquareDrawing();
+        var candidates = strategy.GenerateCandidates(drawing, 0.25, 0.25);
+        Assert.NotEmpty(candidates);
+    }
+
+    [Fact]
+    public void GenerateCandidates_AllCandidatesHaveCorrectDrawing()
+    {
+        var strategy = new NfpSlideStrategy(0, 1, "0 deg NFP");
+        var drawing = TestHelpers.MakeSquareDrawing();
+        var candidates = strategy.GenerateCandidates(drawing, 0.25, 0.25);
+        Assert.All(candidates, c => Assert.Same(drawing, c.Drawing));
+    }
+
+    [Fact]
+    public void GenerateCandidates_Part1RotationIsAlwaysZero()
+    {
+        var strategy = new NfpSlideStrategy(Angle.HalfPI, 1, "90 deg NFP");
+        var drawing = TestHelpers.MakeSquareDrawing();
+        var candidates = strategy.GenerateCandidates(drawing, 0.25, 0.25);
+        Assert.All(candidates, c => Assert.Equal(0, c.Part1Rotation));
+    }
+
+    [Fact]
+    public void GenerateCandidates_Part2RotationMatchesStrategy()
+    {
+        var rotation = Angle.HalfPI;
+        var strategy = new NfpSlideStrategy(rotation, 1, "90 deg NFP");
+        var drawing = TestHelpers.MakeSquareDrawing();
+        var candidates = strategy.GenerateCandidates(drawing, 0.25, 0.25);
+        Assert.All(candidates, c => Assert.Equal(rotation, c.Part2Rotation));
+    }
+
+    [Fact]
+    public void GenerateCandidates_NoDuplicateOffsets()
+    {
+        var strategy = new NfpSlideStrategy(0, 1, "0 deg NFP");
+        var drawing = TestHelpers.MakeSquareDrawing();
+        var candidates = strategy.GenerateCandidates(drawing, 0.25, 0.25);
+
+        var uniqueOffsets = candidates
+            .Select(c => (System.Math.Round(c.Part2Offset.X, 6), System.Math.Round(c.Part2Offset.Y, 6)))
+            .Distinct()
+            .Count();
+        Assert.Equal(candidates.Count, uniqueOffsets);
+    }
+
+    [Fact]
+    public void GenerateCandidates_MoreCandidates_WithSmallerStepSize()
+    {
+        var strategy = new NfpSlideStrategy(0, 1, "0 deg NFP");
+        var drawing = TestHelpers.MakeSquareDrawing();
+        var largeStep = strategy.GenerateCandidates(drawing, 0.25, 5.0);
+        var smallStep = strategy.GenerateCandidates(drawing, 0.25, 0.5);
+        Assert.True(smallStep.Count >= largeStep.Count);
+    }
+
+    [Fact]
+    public void GenerateCandidates_ReturnsEmpty_ForEmptyDrawing()
+    {
+        var strategy = new NfpSlideStrategy(0, 1, "0 deg NFP");
+        var pgm = new Program();
+        var drawing = new Drawing("empty", pgm);
+        var candidates = strategy.GenerateCandidates(drawing, 0.25, 0.25);
+        Assert.Empty(candidates);
+    }
+
+    [Fact]
+    public void GenerateCandidates_LShape_ProducesMoreCandidates_ThanSquare()
+    {
+        var strategy = new NfpSlideStrategy(0, 1, "0 deg NFP");
+        var square = TestHelpers.MakeSquareDrawing();
+        var lshape = TestHelpers.MakeLShapeDrawing();
+
+        var squareCandidates = strategy.GenerateCandidates(square, 0.25, 0.25);
+        var lshapeCandidates = strategy.GenerateCandidates(lshape, 0.25, 0.25);
+
+        Assert.True(lshapeCandidates.Count > squareCandidates.Count);
+    }
+
+    [Fact]
+    public void GenerateCandidates_At180Degrees_ProducesCandidates()
+    {
+        var strategy = new NfpSlideStrategy(System.Math.PI, 1, "180 deg NFP");
+        var drawing = TestHelpers.MakeSquareDrawing();
+        var candidates = strategy.GenerateCandidates(drawing, 0.25, 0.25);
+        Assert.NotEmpty(candidates);
+        Assert.All(candidates, c => Assert.Equal(System.Math.PI, c.Part2Rotation));
+    }
+}