Add missing unit tests, bumps coverage to 99%

X10D.Tests/src/Drawing/CircleFTests.cs

@@ -10,14 +10,14 @@ public class CircleFTests
     public void Area_ShouldBePiRadiusRadius_GivenUnitCircle()
     {
         var unitCircle = CircleF.Unit;
-        Assert.AreEqual(MathF.PI * unitCircle.Radius * unitCircle.Radius, unitCircle.Area);
+        Assert.AreEqual(MathF.PI, unitCircle.Area);
     }
 
     [TestMethod]
     public void Circumference_ShouldBe2PiRadius_GivenUnitCircle()
     {
         var unitCircle = CircleF.Unit;
-        Assert.AreEqual(2.0f * MathF.PI * unitCircle.Radius, unitCircle.Circumference, 1e-6f);
+        Assert.AreEqual(2 * MathF.PI, unitCircle.Circumference, 1e-6f);
     }
 
     [TestMethod]
@@ -32,6 +32,18 @@ public class CircleFTests
         Assert.AreEqual(1, CircleF.Unit.CompareTo(CircleF.Empty));
     }
 
+    [TestMethod]
+    public void CompareTo_ShouldBeNegativeOne_GivenEmptyCircleAndUnitCircleAsObject()
+    {
+        Assert.AreEqual(-1, CircleF.Empty.CompareTo((object)CircleF.Unit));
+    }
+
+    [TestMethod]
+    public void CompareTo_ShouldBeOne_GivenNull()
+    {
+        Assert.AreEqual(1, CircleF.Unit.CompareTo(null));
+    }
+
     [TestMethod]
     public void CompareTo_ShouldBeZero_GivenUnitCircle()
     {
@@ -39,6 +51,12 @@ public class CircleFTests
         Assert.AreEqual(0, unitCircle.CompareTo(unitCircle));
     }
 
+    [TestMethod]
+    public void CompareTo_ShouldThrowArgumentException_GivenInvalidType()
+    {
+        Assert.ThrowsException<ArgumentException>(() => CircleF.Unit.CompareTo(new object()));
+    }
+
     [TestMethod]
     public void Diameter_ShouldBe2_GivenUnitCircle()
     {
@@ -79,6 +97,46 @@ public class CircleFTests
         Assert.AreEqual(hashCode, CircleF.Unit.GetHashCode());
     }
 
+    [TestMethod]
+    public void op_Explicit_ShouldReturnEquivalentCircle_GivenCircle()
+    {
+        CircleF unitCircle = CircleF.Unit;
+        Circle converted = (Circle)unitCircle;
+
+        Assert.AreEqual(unitCircle, converted);
+        Assert.AreEqual(unitCircle.Radius, converted.Radius);
+        Assert.AreEqual(unitCircle.Center, converted.Center);
+    }
+
+    [TestMethod]
+    public void op_GreaterThan_True_GivenUnitAndEmptyCircle()
+    {
+        Assert.IsTrue(CircleF.Unit > CircleF.Empty);
+        Assert.IsTrue(CircleF.Unit >= CircleF.Empty);
+        Assert.IsFalse(CircleF.Unit < CircleF.Empty);
+        Assert.IsFalse(CircleF.Unit <= CircleF.Empty);
+    }
+
+    [TestMethod]
+    public void op_Implicit_ShouldReturnEquivalentCircle_GivenCircle()
+    {
+        Circle unitCircle = Circle.Unit;
+        CircleF converted = unitCircle;
+
+        Assert.AreEqual(unitCircle, converted);
+        Assert.AreEqual(unitCircle.Radius, converted.Radius);
+        Assert.AreEqual(unitCircle.Center, converted.Center);
+    }
+
+    [TestMethod]
+    public void op_LessThan_True_GivenEmptyAndUnitCircle()
+    {
+        Assert.IsTrue(CircleF.Empty < CircleF.Unit);
+        Assert.IsTrue(CircleF.Empty <= CircleF.Unit);
+        Assert.IsFalse(CircleF.Empty > CircleF.Unit);
+        Assert.IsFalse(CircleF.Empty >= CircleF.Unit);
+    }
+
     [TestMethod]
     public void Radius_ShouldBe0_GivenEmptyCircle()
     {

X10D.Tests/src/Drawing/CircleTests.cs

@@ -32,6 +32,18 @@ public class CircleTests
         Assert.AreEqual(1, Circle.Unit.CompareTo(Circle.Empty));
     }
 
+    [TestMethod]
+    public void CompareTo_ShouldBeNegativeOne_GivenEmptyCircleAndUnitCircleAsObject()
+    {
+        Assert.AreEqual(-1, Circle.Empty.CompareTo((object)Circle.Unit));
+    }
+
+    [TestMethod]
+    public void CompareTo_ShouldBeOne_GivenNull()
+    {
+        Assert.AreEqual(1, Circle.Unit.CompareTo(null));
+    }
+
     [TestMethod]
     public void CompareTo_ShouldBeZero_GivenUnitCircle()
     {
@@ -39,6 +51,12 @@ public class CircleTests
         Assert.AreEqual(0, unitCircle.CompareTo(unitCircle));
     }
 
+    [TestMethod]
+    public void CompareTo_ShouldThrowArgumentException_GivenInvalidType()
+    {
+        Assert.ThrowsException<ArgumentException>(() => Circle.Unit.CompareTo(new object()));
+    }
+
     [TestMethod]
     public void Diameter_ShouldBe2_GivenUnitCircle()
     {
@@ -79,6 +97,24 @@ public class CircleTests
         Assert.AreEqual(hashCode, Circle.Unit.GetHashCode());
     }
 
+    [TestMethod]
+    public void op_GreaterThan_True_GivenUnitAndEmptyCircle()
+    {
+        Assert.IsTrue(Circle.Unit > Circle.Empty);
+        Assert.IsTrue(Circle.Unit >= Circle.Empty);
+        Assert.IsFalse(Circle.Unit < Circle.Empty);
+        Assert.IsFalse(Circle.Unit <= Circle.Empty);
+    }
+
+    [TestMethod]
+    public void op_LessThan_True_GivenEmptyAndUnitCircle()
+    {
+        Assert.IsTrue(Circle.Empty < Circle.Unit);
+        Assert.IsTrue(Circle.Empty <= Circle.Unit);
+        Assert.IsFalse(Circle.Empty > Circle.Unit);
+        Assert.IsFalse(Circle.Empty >= Circle.Unit);
+    }
+
     [TestMethod]
     public void Radius_ShouldBe0_GivenEmptyCircle()
     {

X10D.Tests/src/Drawing/LineFTests.cs

@@ -12,6 +12,18 @@ public class LineFTests
         Assert.AreEqual(-1, LineF.Empty.CompareTo(LineF.One));
     }
 
+    [TestMethod]
+    public void CompareTo_ShouldBeNegativeOne_GivenEmptyLineAndOneLineAsObject()
+    {
+        Assert.AreEqual(-1, LineF.Empty.CompareTo((object)LineF.One));
+    }
+
+    [TestMethod]
+    public void CompareTo_ShouldBeOne_GivenNull()
+    {
+        Assert.AreEqual(1, LineF.One.CompareTo(null));
+    }
+
     [TestMethod]
     public void CompareTo_ShouldBeOne_GivenOneAndEmpty()
     {
@@ -25,6 +37,12 @@ public class LineFTests
         Assert.AreEqual(0, unitLineF.CompareTo(unitLineF));
     }
 
+    [TestMethod]
+    public void CompareTo_ShouldThrowArgumentException_GivenInvalidType()
+    {
+        Assert.ThrowsException<ArgumentException>(() => LineF.Empty.CompareTo(new object()));
+    }
+
     [TestMethod]
     public void Length_ShouldBe0_GivenEmptyLine()
     {
@@ -76,4 +94,46 @@ public class LineFTests
         int hashCode = LineF.One.GetHashCode();
         Assert.AreEqual(hashCode, LineF.One.GetHashCode());
     }
+
+    [TestMethod]
+    public void op_Explicit_ShouldReturnEquivalentLine_GivenLine()
+    {
+        LineF oneLine = LineF.One;
+        Line converted = (Line)oneLine;
+
+        Assert.AreEqual(oneLine, converted);
+        Assert.AreEqual(oneLine.Length, converted.Length);
+        Assert.AreEqual(oneLine.Start, converted.Start);
+        Assert.AreEqual(oneLine.End, converted.End);
+    }
+
+    [TestMethod]
+    public void op_GreaterThan_True_GivenUnitAndEmptyCircle()
+    {
+        Assert.IsTrue(LineF.One > LineF.Empty);
+        Assert.IsTrue(LineF.One >= LineF.Empty);
+        Assert.IsFalse(LineF.One < LineF.Empty);
+        Assert.IsFalse(LineF.One <= LineF.Empty);
+    }
+
+    [TestMethod]
+    public void op_Implicit_ShouldReturnEquivalentLine_GivenLine()
+    {
+        Line oneLine = Line.One;
+        LineF converted = oneLine;
+
+        Assert.AreEqual(oneLine, converted);
+        Assert.AreEqual(oneLine.Length, converted.Length);
+        Assert.AreEqual(oneLine.Start, converted.Start);
+        Assert.AreEqual(oneLine.End, converted.End);
+    }
+
+    [TestMethod]
+    public void op_LessThan_True_GivenEmptyAndUnitCircle()
+    {
+        Assert.IsTrue(LineF.Empty < LineF.One);
+        Assert.IsTrue(LineF.Empty <= LineF.One);
+        Assert.IsFalse(LineF.Empty > LineF.One);
+        Assert.IsFalse(LineF.Empty >= LineF.One);
+    }
 }

X10D.Tests/src/Drawing/LineTests.cs

@@ -12,6 +12,18 @@ public class LineTests
         Assert.AreEqual(-1, Line.Empty.CompareTo(Line.One));
     }
 
+    [TestMethod]
+    public void CompareTo_ShouldBeNegativeOne_GivenEmptyLineAndOneLineAsObject()
+    {
+        Assert.AreEqual(-1, Line.Empty.CompareTo((object)Line.One));
+    }
+
+    [TestMethod]
+    public void CompareTo_ShouldBeOne_GivenNull()
+    {
+        Assert.AreEqual(1, Line.One.CompareTo(null));
+    }
+
     [TestMethod]
     public void CompareTo_ShouldBeOne_GivenOneAndEmpty()
     {
@@ -26,21 +38,9 @@ public class LineTests
     }
 
     [TestMethod]
-    public void Length_ShouldBe0_GivenEmptyLine()
+    public void CompareTo_ShouldThrowArgumentException_GivenInvalidType()
     {
-        Assert.AreEqual(0.0f, Line.Empty.Length);
-    }
-
-    [TestMethod]
-    public void Length_ShouldBe1_GivenUnitXLine()
-    {
-        Assert.AreEqual(1.0f, Line.UnitX.Length, 1e-6f);
-    }
-
-    [TestMethod]
-    public void Length_ShouldBe1_GivenUnitYLine()
-    {
-        Assert.AreEqual(1.0f, Line.UnitY.Length, 1e-6f);
+        Assert.ThrowsException<ArgumentException>(() => Line.Empty.CompareTo(new object()));
     }
 
     [TestMethod]
@@ -76,4 +76,40 @@ public class LineTests
         int hashCode = Line.One.GetHashCode();
         Assert.AreEqual(hashCode, Line.One.GetHashCode());
     }
+
+    [TestMethod]
+    public void Length_ShouldBe0_GivenEmptyLine()
+    {
+        Assert.AreEqual(0.0f, Line.Empty.Length);
+    }
+
+    [TestMethod]
+    public void Length_ShouldBe1_GivenUnitXLine()
+    {
+        Assert.AreEqual(1.0f, Line.UnitX.Length, 1e-6f);
+    }
+
+    [TestMethod]
+    public void Length_ShouldBe1_GivenUnitYLine()
+    {
+        Assert.AreEqual(1.0f, Line.UnitY.Length, 1e-6f);
+    }
+
+    [TestMethod]
+    public void op_GreaterThan_True_GivenUnitAndEmptyCircle()
+    {
+        Assert.IsTrue(Line.One > Line.Empty);
+        Assert.IsTrue(Line.One >= Line.Empty);
+        Assert.IsFalse(Line.One < Line.Empty);
+        Assert.IsFalse(Line.One <= Line.Empty);
+    }
+
+    [TestMethod]
+    public void op_LessThan_True_GivenEmptyAndUnitCircle()
+    {
+        Assert.IsTrue(Line.Empty < Line.One);
+        Assert.IsTrue(Line.Empty <= Line.One);
+        Assert.IsFalse(Line.Empty > Line.One);
+        Assert.IsFalse(Line.Empty >= Line.One);
+    }
 }

X10D.Tests/src/Drawing/PolygonFTests.cs

@@ -8,6 +8,107 @@ namespace X10D.Tests.Drawing;
 [TestClass]
 public class PolygonFTests
 {
+    [TestMethod]
+    public void AddPoints_ShouldAddPoints()
+    {
+        var polygon = PolygonF.Empty;
+        polygon.AddPoints(new[] {new PointF(1, 2), new PointF(3, 4)});
+        Assert.AreEqual(2, polygon.PointCount);
+
+        // assert that the empty polygon was not modified
+        Assert.AreEqual(0, PolygonF.Empty.PointCount);
+    }
+
+    [TestMethod]
+    public void ClearPoints_ShouldClearPoints()
+    {
+        var polygon = PolygonF.Empty;
+        polygon.AddPoints(new[] {new Vector2(1, 2), new Vector2(3, 4)});
+        Assert.AreEqual(2, polygon.PointCount);
+
+        // assert that the empty polygon was not modified
+        Assert.AreEqual(0, PolygonF.Empty.PointCount);
+
+        polygon.ClearPoints();
+        Assert.AreEqual(0, polygon.PointCount);
+    }
+
+    [TestMethod]
+    public void Constructor_ShouldPopulatePoints_GivenPolygon()
+    {
+        var pointPolygon = new PolygonF(new[] {new PointF(1, 2), new PointF(3, 4)});
+        var vectorPolygon = new PolygonF(new[] {new Vector2(1, 2), new Vector2(3, 4)});
+
+        Assert.AreEqual(2, pointPolygon.PointCount);
+        Assert.AreEqual(2, vectorPolygon.PointCount);
+    }
+
+    [TestMethod]
+    public void CopyConstructor_ShouldCopyPoints_GivenPolygon()
+    {
+        var first = PolygonF.Empty;
+        first.AddPoints(new[] {new PointF(1, 2), new PointF(3, 4)});
+
+        var second = new PolygonF(first);
+        Assert.AreEqual(2, first.PointCount);
+        Assert.AreEqual(2, second.PointCount);
+
+        // we cannot use CollectionAssert here for reasons I am not entirely sure of.
+        // it seems to dislike casting from IReadOnlyList<Point> to ICollection. but okay.
+        Assert.IsTrue(first.Points.SequenceEqual(second.Points));
+
+        // assert that the empty polygon was not modified
+        Assert.AreEqual(0, PolygonF.Empty.PointCount);
+    }
+
+    [TestMethod]
+    public void Equals_ShouldBeTrue_GivenTwoEmptyPolygons()
+    {
+        var first = PolygonF.Empty;
+        var second = PolygonF.Empty;
+
+        Assert.AreEqual(first, second);
+        Assert.AreEqual(second, first);
+        Assert.IsTrue(first.Equals(second));
+        Assert.IsTrue(second.Equals(first));
+        Assert.IsTrue(first == second);
+        Assert.IsTrue(second == first);
+        Assert.IsFalse(first != second);
+        Assert.IsFalse(second != first);
+    }
+
+    [TestMethod]
+    public void Equals_ShouldBeTrue_GivenTwoHexagons()
+    {
+        PolygonF first = CreateHexagon();
+        PolygonF second = CreateHexagon();
+
+        Assert.AreEqual(first, second);
+        Assert.AreEqual(second, first);
+        Assert.IsTrue(first.Equals(second));
+        Assert.IsTrue(second.Equals(first));
+        Assert.IsTrue(first == second);
+        Assert.IsTrue(second == first);
+        Assert.IsFalse(first != second);
+        Assert.IsFalse(second != first);
+    }
+
+    [TestMethod]
+    public void Equals_ShouldBeFalse_GivenHexagonAndEmptyPolygon()
+    {
+        PolygonF first = CreateHexagon();
+        PolygonF second = PolygonF.Empty;
+
+        Assert.AreNotEqual(first, second);
+        Assert.AreNotEqual(second, first);
+        Assert.IsFalse(first.Equals(second));
+        Assert.IsFalse(second.Equals(first));
+        Assert.IsFalse(first == second);
+        Assert.IsFalse(second == first);
+        Assert.IsTrue(first != second);
+        Assert.IsTrue(second != first);
+    }
+
     [TestMethod]
     public void IsConvex_ShouldBeFalse_GivenEmptyPolygon()
     {
@@ -20,6 +121,38 @@ public class PolygonFTests
         Assert.IsTrue(CreateHexagon().IsConvex);
     }
 
+    [TestMethod]
+    public void IsConvex_ShouldBeFalse_GivenConcavePolygon()
+    {
+        Assert.IsFalse(CreateConcavePolygon().IsConvex);
+    }
+
+    [TestMethod]
+    public void op_Explicit_ShouldReturnEquivalentCircle_GivenCircle()
+    {
+        PolygonF polygon = CreateHexagon();
+        Polygon converted = (Polygon)polygon;
+
+        Assert.AreEqual(polygon, converted);
+        Assert.AreEqual(polygon.IsConvex, converted.IsConvex);
+        Assert.AreEqual(polygon.PointCount, converted.PointCount);
+
+        Assert.IsTrue(polygon.Points.SequenceEqual(converted.Points.Select(p => (PointF)p)));
+    }
+
+    [TestMethod]
+    public void op_Implicit_ShouldReturnEquivalentCircle_GivenCircle()
+    {
+        Polygon polygon = PolygonTests.CreateHexagon();
+        PolygonF converted = polygon;
+
+        Assert.AreEqual(polygon, converted);
+        Assert.AreEqual(polygon.IsConvex, converted.IsConvex);
+        Assert.AreEqual(polygon.PointCount, converted.PointCount);
+
+        Assert.IsTrue(converted.Points.SequenceEqual(polygon.Points.Select(p => (PointF)p)));
+    }
+
     [TestMethod]
     public void PointCount_ShouldBe1_GivenPolygonFWith1Point()
     {
@@ -38,16 +171,6 @@ public class PolygonFTests
         Assert.AreEqual(0, PolygonF.Empty.PointCount);
     }
 
-    [TestMethod]
-    public void Equals_ShouldBeTrue_GivenTwoUnitCircles()
-    {
-        var emptyPolygonF1 = PolygonF.Empty;
-        var emptyPolygonF2 = PolygonF.Empty;
-        Assert.AreEqual(emptyPolygonF1, emptyPolygonF2);
-        Assert.IsTrue(emptyPolygonF1 == emptyPolygonF2);
-        Assert.IsFalse(emptyPolygonF1 != emptyPolygonF2);
-    }
-
     [TestMethod]
     public void GetHashCode_ShouldBeCorrect_GivenEmptyCircle()
     {
@@ -56,7 +179,7 @@ public class PolygonFTests
         Assert.AreEqual(hashCode, PolygonF.Empty.GetHashCode());
     }
 
-    private static PolygonF CreateHexagon()
+    internal static PolygonF CreateHexagon()
     {
         var hexagon = new PolygonF();
         hexagon.AddPoint(new Vector2(0, 0));
@@ -67,4 +190,15 @@ public class PolygonFTests
         hexagon.AddPoint(new Vector2(-1, 0));
         return hexagon;
     }
+
+    internal static PolygonF CreateConcavePolygon()
+    {
+        var hexagon = new PolygonF();
+        hexagon.AddPoint(new Vector2(0, 0));
+        hexagon.AddPoint(new Vector2(2, 0));
+        hexagon.AddPoint(new Vector2(1, 1));
+        hexagon.AddPoint(new Vector2(2, 1));
+        hexagon.AddPoint(new Vector2(0, 1));
+        return hexagon;
+    }
 }

X10D.Tests/src/Drawing/PolygonTests.cs

@@ -7,6 +7,98 @@ namespace X10D.Tests.Drawing;
 [TestClass]
 public class PolygonTests
 {
+    [TestMethod]
+    public void AddPoints_ShouldAddPoints()
+    {
+        var polygon = Polygon.Empty;
+        polygon.AddPoints(new[] {new Point(1, 2), new Point(3, 4)});
+        Assert.AreEqual(2, polygon.PointCount);
+
+
+        // assert that the empty polygon was not modified
+        Assert.AreEqual(0, Polygon.Empty.PointCount);
+    }
+
+    [TestMethod]
+    public void ClearPoints_ShouldClearPoints()
+    {
+        var polygon = Polygon.Empty;
+        polygon.AddPoints(new[] {new Point(1, 2), new Point(3, 4)});
+        Assert.AreEqual(2, polygon.PointCount);
+
+        // assert that the empty polygon was not modified
+        Assert.AreEqual(0, PolygonF.Empty.PointCount);
+
+        polygon.ClearPoints();
+        Assert.AreEqual(0, polygon.PointCount);
+    }
+
+    [TestMethod]
+    public void CopyConstructor_ShouldCopyPoints_GivenPolygon()
+    {
+        var first = Polygon.Empty;
+        first.AddPoints(new[] {new Point(1, 2), new Point(3, 4)});
+
+        var second = new Polygon(first);
+        Assert.AreEqual(2, first.PointCount);
+        Assert.AreEqual(2, second.PointCount);
+
+        // we cannot use CollectionAssert here for reasons I am not entirely sure of.
+        // it seems to dislike casting from IReadOnlyList<Point> to ICollection. but okay.
+        Assert.IsTrue(first.Points.SequenceEqual(second.Points));
+
+        // assert that the empty polygon was not modified
+        Assert.AreEqual(0, Polygon.Empty.PointCount);
+    }
+
+    [TestMethod]
+    public void Equals_ShouldBeTrue_GivenTwoEmptyPolygons()
+    {
+        var first = Polygon.Empty;
+        var second = Polygon.Empty;
+
+        Assert.AreEqual(first, second);
+        Assert.AreEqual(second, first);
+        Assert.IsTrue(first.Equals(second));
+        Assert.IsTrue(second.Equals(first));
+        Assert.IsTrue(first == second);
+        Assert.IsTrue(second == first);
+        Assert.IsFalse(first != second);
+        Assert.IsFalse(second != first);
+    }
+
+    [TestMethod]
+    public void Equals_ShouldBeTrue_GivenTwoHexagons()
+    {
+        Polygon first = CreateHexagon();
+        Polygon second = CreateHexagon();
+
+        Assert.AreEqual(first, second);
+        Assert.AreEqual(second, first);
+        Assert.IsTrue(first.Equals(second));
+        Assert.IsTrue(second.Equals(first));
+        Assert.IsTrue(first == second);
+        Assert.IsTrue(second == first);
+        Assert.IsFalse(first != second);
+        Assert.IsFalse(second != first);
+    }
+
+    [TestMethod]
+    public void Equals_ShouldBeFalse_GivenHexagonAndEmptyPolygon()
+    {
+        Polygon first = CreateHexagon();
+        Polygon second = Polygon.Empty;
+
+        Assert.AreNotEqual(first, second);
+        Assert.AreNotEqual(second, first);
+        Assert.IsFalse(first.Equals(second));
+        Assert.IsFalse(second.Equals(first));
+        Assert.IsFalse(first == second);
+        Assert.IsFalse(second == first);
+        Assert.IsTrue(first != second);
+        Assert.IsTrue(second != first);
+    }
+
     [TestMethod]
     public void IsConvex_ShouldBeFalse_GivenEmptyPolygon()
     {
@@ -19,10 +111,16 @@ public class PolygonTests
         Assert.IsTrue(CreateHexagon().IsConvex);
     }
 
+    [TestMethod]
+    public void IsConvex_ShouldBeFalse_GivenConcavePolygon()
+    {
+        Assert.IsFalse(CreateConcavePolygon().IsConvex);
+    }
+
     [TestMethod]
     public void PointCount_ShouldBe1_GivenPolygonWith1Point()
     {
-        var polygon = new Polygon();
+        var polygon = Polygon.Empty;
         polygon.AddPoint(new Point(1, 1));
 
         Assert.AreEqual(1, polygon.PointCount);
@@ -37,16 +135,6 @@ public class PolygonTests
         Assert.AreEqual(0, Polygon.Empty.PointCount);
     }
 
-    [TestMethod]
-    public void Equals_ShouldBeTrue_GivenTwoUnitCircles()
-    {
-        var emptyPolygon1 = Polygon.Empty;
-        var emptyPolygon2 = Polygon.Empty;
-        Assert.AreEqual(emptyPolygon1, emptyPolygon2);
-        Assert.IsTrue(emptyPolygon1 == emptyPolygon2);
-        Assert.IsFalse(emptyPolygon1 != emptyPolygon2);
-    }
-
     [TestMethod]
     public void GetHashCode_ShouldBeCorrect_GivenEmptyCircle()
     {
@@ -55,7 +143,7 @@ public class PolygonTests
         Assert.AreEqual(hashCode, Polygon.Empty.GetHashCode());
     }
 
-    private static Polygon CreateHexagon()
+    internal static Polygon CreateHexagon()
     {
         var hexagon = new Polygon();
         hexagon.AddPoint(new Point(0, 0));
@@ -66,4 +154,15 @@ public class PolygonTests
         hexagon.AddPoint(new Point(-1, 0));
         return hexagon;
     }
+
+    internal static Polygon CreateConcavePolygon()
+    {
+        var hexagon = new Polygon();
+        hexagon.AddPoint(new Point(0, 0));
+        hexagon.AddPoint(new Point(2, 0));
+        hexagon.AddPoint(new Point(1, 1));
+        hexagon.AddPoint(new Point(2, 1));
+        hexagon.AddPoint(new Point(0, 1));
+        return hexagon;
+    }
 }