diff --git a/X10D.Tests/src/Drawing/CuboidTests.cs b/X10D.Tests/src/Drawing/CuboidTests.cs
new file mode 100644
index 0000000..d879a5b
--- /dev/null
+++ b/X10D.Tests/src/Drawing/CuboidTests.cs
@@ -0,0 +1,76 @@
+using System.Numerics;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using X10D.Drawing;
+
+namespace X10D.Tests.Drawing;
+
+[TestClass]
+public class CuboidTests
+{
+    [TestMethod]
+    public void Corners_ShouldBeCorrect_GivenCubeOfSize1()
+    {
+        Cuboid cube = Cuboid.Cube;
+        
+        Assert.AreEqual(new Vector3(0.5f, 0.5f, -0.5f), cube.FrontTopRight);
+        Assert.AreEqual(new Vector3(-0.5f, 0.5f, -0.5f), cube.FrontTopLeft);
+        Assert.AreEqual(new Vector3(0.5f, -0.5f, -0.5f), cube.FrontBottomRight);
+        Assert.AreEqual(new Vector3(-0.5f, -0.5f, -0.5f), cube.FrontBottomLeft);
+        Assert.AreEqual(new Vector3(0.5f, 0.5f, 0.5f), cube.BackTopRight);
+        Assert.AreEqual(new Vector3(-0.5f, 0.5f, 0.5f), cube.BackTopLeft);
+        Assert.AreEqual(new Vector3(0.5f, -0.5f, 0.5f), cube.BackBottomRight);
+        Assert.AreEqual(new Vector3(-0.5f, -0.5f, 0.5f), cube.BackBottomLeft);
+    }
+
+    [TestMethod]
+    public void Equals_ShouldBeTrue_GivenTwoCubesOfSize1()
+    {
+        var cube1 = Cuboid.Cube;
+        var cube2 = Cuboid.Cube;
+        Assert.AreEqual(cube1, cube2);
+        Assert.IsTrue(cube1 == cube2);
+        Assert.IsFalse(cube1 != cube2);
+    }
+
+    [TestMethod]
+    public void Equals_ShouldBeFalse_GivenDifferentCubes()
+    {
+        Assert.AreNotEqual(Cuboid.Cube, Cuboid.Empty);
+        Assert.IsFalse(Cuboid.Cube == Cuboid.Empty);
+        Assert.IsTrue(Cuboid.Cube != Cuboid.Empty);
+    }
+
+    [TestMethod]
+    public void GetHashCode_ShouldBeCorrect_GivenEmptyCircle()
+    {
+        // this test is pretty pointless, it exists only for code coverage purposes
+        int hashCode = Cuboid.Empty.GetHashCode();
+        Assert.AreEqual(hashCode, Cuboid.Empty.GetHashCode());
+    }
+
+    [TestMethod]
+    public void GetHashCode_ShouldBeCorrect_GivenCubeOfSize1()
+    {
+        // this test is pretty pointless, it exists only for code coverage purposes
+        int hashCode = Cuboid.Cube.GetHashCode();
+        Assert.AreEqual(hashCode, Cuboid.Cube.GetHashCode());
+    }
+
+    [TestMethod]
+    public void Size_ShouldBeOne_GivenCubeOfSize1()
+    {
+        Assert.AreEqual(Vector3.One, Cuboid.Cube.Size);
+    }
+
+    [TestMethod]
+    public void Size_ShouldBeOne_GivenRotatedCube()
+    {
+        Assert.AreEqual(Vector3.One, new Cuboid(0, 0, 0, 1, 1, 1, 90, 0, 0).Size);
+    }
+
+    [TestMethod]
+    public void Volume_ShouldBe1_GivenCubeOfSize1()
+    {
+        Assert.AreEqual(1.0f, Cuboid.Cube.Volume, 1e-6f);
+    }
+}
diff --git a/X10D.Tests/src/Drawing/PolyhedronTests.cs b/X10D.Tests/src/Drawing/PolyhedronTests.cs
new file mode 100644
index 0000000..9d72ec0
--- /dev/null
+++ b/X10D.Tests/src/Drawing/PolyhedronTests.cs
@@ -0,0 +1,188 @@
+using System.Numerics;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using X10D.Drawing;
+
+namespace X10D.Tests.Drawing;
+
+[TestClass]
+public class PolyhedronTests
+{
+    [TestMethod]
+    public void AddVertices_ShouldAddVertices()
+    {
+        var polyhedron = Polyhedron.Empty;
+        polyhedron.AddVertices(new[] {new Vector3(1, 2, 3), new Vector3(4, 5, 6)});
+        Assert.AreEqual(2, polyhedron.VertexCount);
+
+        // assert that the empty polyhedron was not modified
+        Assert.AreEqual(0, Polyhedron.Empty.VertexCount);
+    }
+
+    [TestMethod]
+    public void ClearVertices_ShouldClearVertices()
+    {
+        var polyhedron = Polyhedron.Empty;
+        polyhedron.AddVertices(new[] {new Vector3(1, 2, 3), new Vector3(4, 5, 6)});
+        Assert.AreEqual(2, polyhedron.VertexCount);
+
+        // assert that the empty polyhedron was not modified
+        Assert.AreEqual(0, Polyhedron.Empty.VertexCount);
+
+        polyhedron.ClearVertices();
+        Assert.AreEqual(0, polyhedron.VertexCount);
+    }
+
+    [TestMethod]
+    public void Constructor_ShouldPopulateVertices_GivenPolyhedron()
+    {
+        var polyhedron = new Polyhedron(new[] {new Vector3(1, 2, 3), new Vector3(4, 5, 6)});
+        Assert.AreEqual(2, polyhedron.VertexCount);
+    }
+
+    [TestMethod]
+    public void CopyConstructor_ShouldCopyVertices_GivenPolyhedron()
+    {
+        var first = Polyhedron.Empty;
+        first.AddVertices(new[] {new Vector3(1, 2, 3), new Vector3(4, 5, 6)});
+
+        var second = new Polyhedron(first);
+        Assert.AreEqual(2, first.VertexCount);
+        Assert.AreEqual(2, second.VertexCount);
+
+        // 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.Vertices.SequenceEqual(second.Vertices));
+
+        // assert that the empty polyhedron was not modified
+        Assert.AreEqual(0, Polyhedron.Empty.VertexCount);
+    }
+
+    [TestMethod]
+    public void Equals_ShouldBeTrue_GivenTwoEmptyPolyhedrons()
+    {
+        var first = Polyhedron.Empty;
+        var second = Polyhedron.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()
+    {
+        Polyhedron first = CreateHexagon();
+        Polyhedron 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_GivenHexagonAndEmptyPolyhedron()
+    {
+        Polyhedron first = CreateHexagon();
+        Polyhedron second = Polyhedron.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 op_Implicit_ShouldReturnEquivalentPolyhedron_GivenPolyhedron()
+    {
+        Polygon polygon = PolygonTests.CreateHexagon();
+        Polyhedron converted = polygon;
+
+        Assert.AreEqual(polygon, converted);
+        Assert.AreEqual(polygon.VertexCount, converted.VertexCount);
+
+        Assert.IsTrue(converted.Vertices.SequenceEqual(polygon.Vertices.Select(p =>
+        {
+            var point = p.ToVector2();
+            return new Vector3(point.X, point.Y, 0);
+        })));
+    }
+
+    [TestMethod]
+    public void op_Implicit_ShouldReturnEquivalentPolyhedron_GivenPolyhedronF()
+    {
+        PolygonF polygon = PolygonFTests.CreateHexagon();
+        Polyhedron converted = polygon;
+
+        Assert.AreEqual(polygon, converted);
+        Assert.AreEqual(polygon.VertexCount, converted.VertexCount);
+
+        Assert.IsTrue(converted.Vertices.SequenceEqual(polygon.Vertices.Select(v =>
+        {
+            var point = v.ToVector2();
+            return new Vector3(point.X, point.Y, 0);
+        })));
+    }
+
+    [TestMethod]
+    public void PointCount_ShouldBe1_GivenPolyhedronWith1Point()
+    {
+        var polyhedron = new Polyhedron();
+        polyhedron.AddVertex(Vector3.One);
+
+        Assert.AreEqual(1, polyhedron.VertexCount);
+
+        // assert that the empty polyhedron was not modified
+        Assert.AreEqual(0, Polyhedron.Empty.VertexCount);
+    }
+
+    [TestMethod]
+    public void PointCount_ShouldBe0_GivenEmptyPolyhedron()
+    {
+        Assert.AreEqual(0, Polyhedron.Empty.VertexCount);
+    }
+
+    [TestMethod]
+    public void GetHashCode_ShouldBeCorrect_GivenEmptyCircle()
+    {
+        // this test is pretty pointless, it exists only for code coverage purposes
+        int hashCode = Polyhedron.Empty.GetHashCode();
+        Assert.AreEqual(hashCode, Polyhedron.Empty.GetHashCode());
+    }
+
+    internal static Polyhedron CreateHexagon()
+    {
+        var hexagon = new Polyhedron();
+        hexagon.AddVertex(new Vector3(0, 0, 0));
+        hexagon.AddVertex(new Vector3(1, 0, 0));
+        hexagon.AddVertex(new Vector3(1, 1, 0));
+        hexagon.AddVertex(new Vector3(0, 1, 0));
+        hexagon.AddVertex(new Vector3(-1, 1, 0));
+        hexagon.AddVertex(new Vector3(-1, 0, 0));
+        return hexagon;
+    }
+
+    internal static Polyhedron CreateConcavePolyhedron()
+    {
+        var hexagon = new Polyhedron();
+        hexagon.AddVertex(new Vector3(0, 0, 0));
+        hexagon.AddVertex(new Vector3(2, 0, 0));
+        hexagon.AddVertex(new Vector3(2, 1, 0));
+        hexagon.AddVertex(new Vector3(2, 1, 0));
+        hexagon.AddVertex(new Vector3(0, 1, 0));
+        return hexagon;
+    }
+}
diff --git a/X10D.Tests/src/Drawing/SphereTests.cs b/X10D.Tests/src/Drawing/SphereTests.cs
new file mode 100644
index 0000000..32b321f
--- /dev/null
+++ b/X10D.Tests/src/Drawing/SphereTests.cs
@@ -0,0 +1,129 @@
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using X10D.Drawing;
+
+namespace X10D.Tests.Drawing;
+
+[TestClass]
+public class SphereTests
+{
+    [TestMethod]
+    public void Circumference_ShouldBe2PiRadius_GivenUnitCircle()
+    {
+        var unitSphere = Sphere.Unit;
+        Assert.AreEqual(2.0f * MathF.PI * unitSphere.Radius, unitSphere.Circumference, 1e-6f);
+    }
+
+    [TestMethod]
+    public void CompareTo_ShouldBeNegativeOne_GivenUnitCircleAndEmpty()
+    {
+        Assert.AreEqual(-1, Sphere.Empty.CompareTo(Sphere.Unit));
+    }
+
+    [TestMethod]
+    public void CompareTo_ShouldBeOne_GivenUnitCircleAndEmpty()
+    {
+        Assert.AreEqual(1, Sphere.Unit.CompareTo(Sphere.Empty));
+    }
+
+    [TestMethod]
+    public void CompareTo_ShouldBeNegativeOne_GivenEmptyCircleAndUnitCircleAsObject()
+    {
+        Assert.AreEqual(-1, Sphere.Empty.CompareTo((object)Sphere.Unit));
+    }
+
+    [TestMethod]
+    public void CompareTo_ShouldBeOne_GivenNull()
+    {
+        Assert.AreEqual(1, Sphere.Unit.CompareTo(null));
+    }
+
+    [TestMethod]
+    public void CompareTo_ShouldBeZero_GivenUnitCircle()
+    {
+        var unitCircle = Sphere.Unit;
+        Assert.AreEqual(0, unitCircle.CompareTo(unitCircle));
+    }
+
+    [TestMethod]
+    public void CompareTo_ShouldThrowArgumentException_GivenInvalidType()
+    {
+        Assert.ThrowsException<ArgumentException>(() => Sphere.Unit.CompareTo(new object()));
+    }
+
+    [TestMethod]
+    public void Diameter_ShouldBe2_GivenUnitSphere()
+    {
+        Assert.AreEqual(2.0f, Sphere.Unit.Diameter, 1e-6f);
+    }
+
+    [TestMethod]
+    public void Equals_ShouldBeTrue_GivenTwoUnitCircles()
+    {
+        var unitCircle1 = Sphere.Unit;
+        var unitCircle2 = Sphere.Unit;
+        Assert.AreEqual(unitCircle1, unitCircle2);
+        Assert.IsTrue(unitCircle1 == unitCircle2);
+        Assert.IsFalse(unitCircle1 != unitCircle2);
+    }
+
+    [TestMethod]
+    public void Equals_ShouldBeFalse_GivenDifferentCircles()
+    {
+        Assert.AreNotEqual(Sphere.Unit, Sphere.Empty);
+        Assert.IsFalse(Sphere.Unit == Sphere.Empty);
+        Assert.IsTrue(Sphere.Unit != Sphere.Empty);
+    }
+
+    [TestMethod]
+    public void GetHashCode_ShouldBeCorrect_GivenEmptyCircle()
+    {
+        // this test is pretty pointless, it exists only for code coverage purposes
+        int hashCode = Sphere.Empty.GetHashCode();
+        Assert.AreEqual(hashCode, Sphere.Empty.GetHashCode());
+    }
+
+    [TestMethod]
+    public void GetHashCode_ShouldBeCorrect_GivenUnitCircle()
+    {
+        // this test is pretty pointless, it exists only for code coverage purposes
+        int hashCode = Sphere.Unit.GetHashCode();
+        Assert.AreEqual(hashCode, Sphere.Unit.GetHashCode());
+    }
+
+    [TestMethod]
+    public void op_GreaterThan_True_GivenUnitAndEmptyCircle()
+    {
+        Assert.IsTrue(Sphere.Unit > Sphere.Empty);
+        Assert.IsTrue(Sphere.Unit >= Sphere.Empty);
+        Assert.IsFalse(Sphere.Unit < Sphere.Empty);
+        Assert.IsFalse(Sphere.Unit <= Sphere.Empty);
+    }
+
+    [TestMethod]
+    public void op_LessThan_True_GivenEmptyAndUnitCircle()
+    {
+        Assert.IsTrue(Sphere.Empty < Sphere.Unit);
+        Assert.IsTrue(Sphere.Empty <= Sphere.Unit);
+        Assert.IsFalse(Sphere.Empty > Sphere.Unit);
+        Assert.IsFalse(Sphere.Empty >= Sphere.Unit);
+    }
+
+    [TestMethod]
+    public void Radius_ShouldBe0_GivenEmptySphere()
+    {
+        Assert.AreEqual(0, Sphere.Empty.Radius);
+    }
+
+    [TestMethod]
+    public void Radius_ShouldBe1_GivenUnitSphere()
+    {
+        Assert.AreEqual(1, Sphere.Unit.Radius);
+    }
+
+    [TestMethod]
+    public void Volume_ShouldBe4Over3TimesPi_GivenUnitCircle()
+    {
+        var unitSphere = Sphere.Unit;
+        Assert.AreEqual(4.0f / 3.0f * MathF.PI, unitSphere.Volume);
+    }
+}