test: add FillTests for full plate fill and remainder strip refill

Added Xunit.SkippableFact package for conditional test skipping when
test data is unavailable.

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

OpenNest.Test/FillTests.cs

@@ -0,0 +1,71 @@
+using OpenNest.Geometry;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace OpenNest.Test;
+
+public class FillTests
+{
+    private readonly ITestOutputHelper _output;
+
+    public FillTests(ITestOutputHelper output)
+    {
+        _output = output;
+    }
+
+    [SkippableFact]
+    [Trait("Category", "Fill")]
+    public void N0308_008_HingePlate_FillsAtLeast75()
+    {
+        Skip.IfNot(TestData.IsAvailable, TestData.SkipReason);
+
+        var nest = TestData.LoadNest("N0308-008.zip");
+        var hinge = nest.Drawings.First(d => d.Name.Contains("HINGE PLATE #2"));
+        var plate = TestData.CleanPlateFrom(nest.Plates[0]);
+
+        var engine = new NestEngine(plate);
+        var sw = System.Diagnostics.Stopwatch.StartNew();
+        engine.Fill(new NestItem { Drawing = hinge, Quantity = 0 });
+        sw.Stop();
+
+        _output.WriteLine($"Parts: {plate.Parts.Count} | Time: {sw.ElapsedMilliseconds}ms");
+
+        Assert.True(plate.Parts.Count >= 75,
+            $"Expected >= 75 parts, got {plate.Parts.Count}");
+        AssertNoOverlaps(plate.Parts.ToList());
+    }
+
+    [SkippableFact]
+    [Trait("Category", "Fill")]
+    public void RemainderStripRefill_30pcs_FillsAtLeast32()
+    {
+        Skip.IfNot(TestData.IsAvailable, TestData.SkipReason);
+
+        var nest = TestData.LoadNest("30pcs Fill.zip");
+        var drawing = nest.Drawings.First();
+        var plate = TestData.CleanPlateFrom(nest.Plates[0]);
+
+        var engine = new NestEngine(plate);
+        var sw = System.Diagnostics.Stopwatch.StartNew();
+        engine.Fill(new NestItem { Drawing = drawing, Quantity = 0 });
+        sw.Stop();
+
+        _output.WriteLine($"Parts: {plate.Parts.Count} | Time: {sw.ElapsedMilliseconds}ms");
+
+        Assert.True(plate.Parts.Count >= 32,
+            $"Expected >= 32 parts, got {plate.Parts.Count}");
+        AssertNoOverlaps(plate.Parts.ToList());
+    }
+
+    private void AssertNoOverlaps(List<Part> parts)
+    {
+        for (var i = 0; i < parts.Count; i++)
+        {
+            for (var j = i + 1; j < parts.Count; j++)
+            {
+                if (parts[i].Intersects(parts[j], out _))
+                    Assert.Fail($"Overlap detected: part [{i}] vs [{j}]");
+            }
+        }
+    }
+}

OpenNest.Test/OpenNest.Test.csproj

@@ -12,6 +12,7 @@
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.*" />
     <PackageReference Include="xunit" Version="2.*" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.*" />
+    <PackageReference Include="Xunit.SkippableFact" Version="1.*" />
   </ItemGroup>
 
   <ItemGroup>