initial commit

tests/TraceCad.Tests/GeometryTests.cs

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+using TraceCad.Core.Geometry;
+using TraceCad.Core.Model;
+using Xunit;
+
+namespace TraceCad.Tests;
+
+public sealed class GeometryTests
+{
+    [Fact]
+    public void LineLengthUsesMillimetres()
+    {
+        var line = new LineEntity(Guid.NewGuid(), Layer.Cut.Name, new Point2(0, 0), new Point2(3, 4));
+
+        Assert.Equal(5.0, line.Length, 9);
+    }
+
+    [Fact]
+    public void CircleFromThreePointsComputesCenterAndRadius()
+    {
+        var success = GeometryHelpers.TryCreateCircleFromThreePoints(
+            new Point2(1, 0),
+            new Point2(0, 1),
+            new Point2(-1, 0),
+            out var circle);
+
+        Assert.True(success);
+        Assert.Equal(0.0, circle.Center.X, 9);
+        Assert.Equal(0.0, circle.Center.Y, 9);
+        Assert.Equal(1.0, circle.Radius, 9);
+    }
+
+    [Fact]
+    public void CircleFromCollinearPointsFails()
+    {
+        var success = GeometryHelpers.TryCreateCircleFromThreePoints(
+            new Point2(0, 0),
+            new Point2(1, 1),
+            new Point2(2, 2),
+            out _);
+
+        Assert.False(success);
+    }
+
+    [Fact]
+    public void ArcFromThreePointsPreservesPointOnCounterClockwiseSweep()
+    {
+        var success = GeometryHelpers.TryCreateArcFromThreePoints(
+            new Point2(1, 0),
+            new Point2(0, 1),
+            new Point2(-1, 0),
+            out var arc);
+
+        Assert.True(success);
+        Assert.False(arc.IsClockwise);
+        Assert.Equal(0.0, arc.StartAngleDeg, 9);
+        Assert.Equal(180.0, arc.EndAngleDeg, 9);
+        Assert.Equal(1.0, arc.Radius, 9);
+    }
+
+    [Fact]
+    public void ArcFromCollinearPointsFails()
+    {
+        var success = GeometryHelpers.TryCreateArcFromThreePoints(
+            new Point2(0, 0),
+            new Point2(5, 0),
+            new Point2(10, 0),
+            out _);
+
+        Assert.False(success);
+    }
+
+    [Theory]
+    [InlineData(360, 0)]
+    [InlineData(-90, 270)]
+    [InlineData(725, 5)]
+    public void AngleNormalizationWrapsToPositiveDegrees(double input, double expected)
+    {
+        Assert.Equal(expected, GeometryHelpers.NormalizeAngleDeg(input), 9);
+    }
+}