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+# OpenNest xUnit Test Suite Implementation Plan
+
+> **For Claude:** REQUIRED SUB-SKILL: Use superpowers:executing-plans to implement this plan task-by-task.
+
+**Goal:** Convert the ad-hoc OpenNest.Test console harness into a proper xUnit test suite with test data hosted in a separate git repo.
+
+**Architecture:** Replace the console app with an xUnit test project. A `TestData` helper resolves the test data path from env var `OPENNEST_TEST_DATA` or fallback `../OpenNest.Test.Data/`. Tests skip with a message if data is missing. Test classes: `FillTests` (full plate fills), `RemnantFillTests` (filling remnant areas). All tests assert part count >= target and zero overlaps.
+
+**Tech Stack:** C# / .NET 8, xUnit, OpenNest.Core + Engine + IO
+
+---
+
+### Task 1: Set up test data repo and push fixture files
+
+**Step 1: Clone the empty repo next to OpenNest**
+
+```bash
+cd C:/Users/AJ/Desktop/Projects
+git clone https://git.thecozycat.net/aj/OpenNest.Test.git OpenNest.Test.Data
+```
+
+**Step 2: Copy fixture files into the repo**
+
+```bash
+cp ~/Desktop/"N0308-017.zip" OpenNest.Test.Data/
+cp ~/Desktop/"N0308-008.zip" OpenNest.Test.Data/
+cp ~/Desktop/"30pcs Fill.zip" OpenNest.Test.Data/
+```
+
+**Step 3: Commit and push**
+
+```bash
+cd OpenNest.Test.Data
+git add .
+git commit -m "feat: add initial test fixture nest files"
+git push
+```
+
+---
+
+### Task 2: Convert OpenNest.Test from console app to xUnit project
+
+**Files:**
+- Modify: `OpenNest.Test/OpenNest.Test.csproj`
+- Delete: `OpenNest.Test/Program.cs`
+- Create: `OpenNest.Test/TestData.cs`
+
+**Step 1: Replace the csproj with xUnit configuration**
+
+Overwrite `OpenNest.Test/OpenNest.Test.csproj`:
+
+```xml
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net8.0-windows</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <IsPackable>false</IsPackable>
+    <IsTestProject>true</IsTestProject>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.*" />
+    <PackageReference Include="xunit" Version="2.*" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.*" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\OpenNest.Core\OpenNest.Core.csproj" />
+    <ProjectReference Include="..\OpenNest.Engine\OpenNest.Engine.csproj" />
+    <ProjectReference Include="..\OpenNest.IO\OpenNest.IO.csproj" />
+  </ItemGroup>
+
+</Project>
+```
+
+**Step 2: Delete Program.cs**
+
+```bash
+rm OpenNest.Test/Program.cs
+```
+
+**Step 3: Create TestData helper**
+
+Create `OpenNest.Test/TestData.cs`:
+
+```csharp
+using OpenNest.IO;
+
+namespace OpenNest.Test;
+
+public static class TestData
+{
+    private static readonly string? BasePath = ResolveBasePath();
+
+    public static bool IsAvailable => BasePath != null;
+
+    public static string SkipReason =>
+        "Test data not found. Set OPENNEST_TEST_DATA env var or clone " +
+        "https://git.thecozycat.net/aj/OpenNest.Test.git to ../OpenNest.Test.Data/";
+
+    public static string GetPath(string filename)
+    {
+        if (BasePath == null)
+            throw new InvalidOperationException(SkipReason);
+
+        var path = Path.Combine(BasePath, filename);
+
+        if (!File.Exists(path))
+            throw new FileNotFoundException($"Test fixture not found: {path}");
+
+        return path;
+    }
+
+    public static Nest LoadNest(string filename)
+    {
+        var reader = new NestReader(GetPath(filename));
+        return reader.Read();
+    }
+
+    public static Plate CleanPlateFrom(Plate reference)
+    {
+        var plate = new Plate();
+        plate.Size = reference.Size;
+        plate.PartSpacing = reference.PartSpacing;
+        plate.EdgeSpacing = reference.EdgeSpacing;
+        plate.Quadrant = reference.Quadrant;
+        return plate;
+    }
+
+    private static string? ResolveBasePath()
+    {
+        // 1. Environment variable
+        var envPath = Environment.GetEnvironmentVariable("OPENNEST_TEST_DATA");
+
+        if (!string.IsNullOrEmpty(envPath) && Directory.Exists(envPath))
+            return envPath;
+
+        // 2. Sibling directory (../OpenNest.Test.Data/ relative to solution root)
+        var dir = AppContext.BaseDirectory;
+
+        // Walk up from bin/Debug/net8.0-windows to find the solution root.
+        for (var i = 0; i < 6; i++)
+        {
+            var parent = Directory.GetParent(dir);
+
+            if (parent == null)
+                break;
+
+            dir = parent.FullName;
+            var candidate = Path.Combine(dir, "OpenNest.Test.Data");
+
+            if (Directory.Exists(candidate))
+                return candidate;
+        }
+
+        return null;
+    }
+}
+```
+
+**Step 4: Build**
+
+Run: `dotnet build OpenNest.Test/OpenNest.Test.csproj`
+Expected: Build succeeds.
+
+**Step 5: Commit**
+
+```bash
+git add OpenNest.Test/
+git commit -m "refactor: convert OpenNest.Test to xUnit project with TestData helper"
+```
+
+---
+
+### Task 3: Add FillTests
+
+**Files:**
+- Create: `OpenNest.Test/FillTests.cs`
+
+**Step 1: Create FillTests.cs**
+
+```csharp
+using OpenNest.Geometry;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace OpenNest.Test;
+
+public class FillTests
+{
+    private readonly ITestOutputHelper _output;
+
+    public FillTests(ITestOutputHelper output)
+    {
+        _output = output;
+    }
+
+    [Fact]
+    [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,
+            $"Expected >= 75 parts, got {plate.Parts.Count}");
+        AssertNoOverlaps(plate.Parts.ToList());
+    }
+
+    [Fact]
+    [Trait("Category", "Fill")]
+    public void RemainderStripRefill_30pcs_FillsAtLeast32()
+    {
+        Skip.IfNot(TestData.IsAvailable, TestData.SkipReason);
+
+        var nest = TestData.LoadNest("30pcs Fill.zip");
+        var drawing = nest.Drawings.First();
+        var plate = TestData.CleanPlateFrom(nest.Plates[0]);
+
+        var engine = new NestEngine(plate);
+        var sw = System.Diagnostics.Stopwatch.StartNew();
+        engine.Fill(new NestItem { Drawing = drawing, Quantity = 0 });
+        sw.Stop();
+
+        _output.WriteLine($"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}]");
+            }
+        }
+    }
+}
+```
+
+**Step 2: Run tests**
+
+Run: `dotnet test OpenNest.Test/ -v normal`
+Expected: 2 tests pass (or skip if data missing).
+
+**Step 3: Commit**
+
+```bash
+git add OpenNest.Test/FillTests.cs
+git commit -m "test: add FillTests for full plate fill and remainder strip refill"
+```
+
+---
+
+### Task 4: Add RemnantFillTests
+
+**Files:**
+- Create: `OpenNest.Test/RemnantFillTests.cs`
+
+**Step 1: Create RemnantFillTests.cs**
+
+```csharp
+using OpenNest.Geometry;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace OpenNest.Test;
+
+public class RemnantFillTests
+{
+    private readonly ITestOutputHelper _output;
+
+    public RemnantFillTests(ITestOutputHelper output)
+    {
+        _output = output;
+    }
+
+    [Fact]
+    [Trait("Category", "Remnant")]
+    public void N0308_017_PT02_RemnantFillsAtLeast10()
+    {
+        Skip.IfNot(TestData.IsAvailable, TestData.SkipReason);
+
+        var nest = TestData.LoadNest("N0308-017.zip");
+        var plate = nest.Plates[0];
+        var pt02 = nest.Drawings.First(d => d.Name.Contains("PT02"));
+        var remnant = plate.GetRemnants()[0];
+
+        _output.WriteLine($"Remnant: ({remnant.X:F2},{remnant.Y:F2}) {remnant.Width:F2}x{remnant.Height:F2}");
+
+        var countBefore = plate.Parts.Count;
+        var engine = new NestEngine(plate);
+        var sw = System.Diagnostics.Stopwatch.StartNew();
+        engine.Fill(new NestItem { Drawing = pt02, Quantity = 0 }, remnant);
+        sw.Stop();
+
+        var added = plate.Parts.Count - countBefore;
+        _output.WriteLine($"Added: {added} parts | Time: {sw.ElapsedMilliseconds}ms");
+
+        Assert.True(added >= 10, $"Expected >= 10 parts in remnant, got {added}");
+
+        var newParts = plate.Parts.Skip(countBefore).ToList();
+        AssertNoOverlaps(newParts);
+        AssertNoCrossOverlaps(plate.Parts.Take(countBefore).ToList(), newParts);
+    }
+
+    [Fact]
+    [Trait("Category", "Remnant")]
+    public void N0308_008_HingePlate_RemnantFillsAtLeast8()
+    {
+        Skip.IfNot(TestData.IsAvailable, TestData.SkipReason);
+
+        var nest = TestData.LoadNest("N0308-008.zip");
+        var plate = nest.Plates[0];
+        var hinge = nest.Drawings.First(d => d.Name.Contains("HINGE PLATE #2"));
+        var remnants = plate.GetRemnants();
+
+        _output.WriteLine($"Remnant 0: ({remnants[0].X:F2},{remnants[0].Y:F2}) {remnants[0].Width:F2}x{remnants[0].Height:F2}");
+
+        var countBefore = plate.Parts.Count;
+        var engine = new NestEngine(plate);
+        var sw = System.Diagnostics.Stopwatch.StartNew();
+        engine.Fill(new NestItem { Drawing = hinge, Quantity = 0 }, remnants[0]);
+        sw.Stop();
+
+        var added = plate.Parts.Count - countBefore;
+        _output.WriteLine($"Added: {added} parts | Time: {sw.ElapsedMilliseconds}ms");
+
+        Assert.True(added >= 8, $"Expected >= 8 parts in remnant, got {added}");
+
+        var newParts = plate.Parts.Skip(countBefore).ToList();
+        AssertNoOverlaps(newParts);
+        AssertNoCrossOverlaps(plate.Parts.Take(countBefore).ToList(), newParts);
+    }
+
+    private void AssertNoOverlaps(List<Part> parts)
+    {
+        for (var i = 0; i < parts.Count; i++)
+        {
+            for (var j = i + 1; j < parts.Count; j++)
+            {
+                if (parts[i].Intersects(parts[j], out _))
+                    Assert.Fail($"Overlap detected: part [{i}] vs [{j}]");
+            }
+        }
+    }
+
+    private void AssertNoCrossOverlaps(List<Part> existing, List<Part> added)
+    {
+        for (var i = 0; i < existing.Count; i++)
+        {
+            for (var j = 0; j < added.Count; j++)
+            {
+                if (existing[i].Intersects(added[j], out _))
+                    Assert.Fail($"Cross-overlap: existing [{i}] vs added [{j}]");
+            }
+        }
+    }
+}
+```
+
+**Step 2: Run all tests**
+
+Run: `dotnet test OpenNest.Test/ -v normal`
+Expected: 4 tests pass.
+
+**Step 3: Commit**
+
+```bash
+git add OpenNest.Test/RemnantFillTests.cs
+git commit -m "test: add RemnantFillTests for remnant area filling"
+```
+
+---
+
+### Task 5: Add test project to solution and final verification
+
+**Step 1: Add to solution**
+
+```bash
+cd C:/Users/AJ/Desktop/Projects/OpenNest
+dotnet sln OpenNest.sln add OpenNest.Test/OpenNest.Test.csproj
+```
+
+**Step 2: Build entire solution**
+
+Run: `dotnet build OpenNest.sln`
+Expected: All projects build, 0 errors.
+
+**Step 3: Run all tests**
+
+Run: `dotnet test OpenNest.sln -v normal`
+Expected: 4 tests pass, 0 failures.
+
+**Step 4: Commit**
+
+```bash
+git add OpenNest.sln
+git commit -m "chore: add OpenNest.Test to solution"
+```