diff --git a/scripts/build-geometry-unity-package.ps1 b/scripts/build-geometry-unity-package.ps1
index 31002f5e..27f3c567 100644
--- a/scripts/build-geometry-unity-package.ps1
+++ b/scripts/build-geometry-unity-package.ps1
@@ -61,6 +61,8 @@ $requiredTemplateFiles = @(
   "Runtime\Unity\GameCult.Geometry.Unity.asmdef",
   "Runtime\Unity\PlanetaryPatchMeshAdapter.cs",
   "Runtime\Unity\PlanetaryPageUpload.cs",
+  "Tests\Editor\GameCult.Geometry.Tests.Editor.asmdef",
+  "Tests\Editor\GeometryPackageTests.cs",
   "Shaders\AdvancedErosionFilter.hlsl",
   "Shaders\GameCult.Geometry.hlsl",
   "Shaders\Planetary.hlsl",
@@ -85,6 +87,12 @@ if ($missingAssetMetas.Count -ne 0 -or $missingDirectoryMetas.Count -ne 0) {
   throw "Tracked Geometry Unity package has assets without stable .meta files: $($missing -join ', ')"
 }
 
+$assemblyDirectories = @($unityAssetFiles | Where-Object { $_.Extension -eq ".asmdef" } | Group-Object DirectoryName)
+$duplicateAssemblyDirectories = @($assemblyDirectories | Where-Object { $_.Count -ne 1 })
+if ($duplicateAssemblyDirectories.Count -ne 0) {
+  throw "Each Geometry Unity assembly directory must contain exactly one asmdef: $($duplicateAssemblyDirectories.Name -join ', ')"
+}
+
 $templateManifest = Get-Content -LiteralPath (Join-Path $templateRoot "package.json") -Raw | ConvertFrom-Json
 $expectedFileVersion = "$($templateManifest.version).0"
 $trackedAssembly = Join-Path $templatePluginRoot "GameCult.Geometry.dll"
diff --git a/unity/org.gamecult.geometry/Tests.meta b/unity/org.gamecult.geometry/Tests.meta
new file mode 100644
index 00000000..68cfab58
--- /dev/null
+++ b/unity/org.gamecult.geometry/Tests.meta
@@ -0,0 +1,8 @@
+fileFormatVersion: 2
+guid: 97ae3726627d441b8d85e69d4ea804b9
+folderAsset: yes
+DefaultImporter:
+  externalObjects: {}
+  userData:
+  assetBundleName:
+  assetBundleVariant:
diff --git a/unity/org.gamecult.geometry/Tests/Editor.meta b/unity/org.gamecult.geometry/Tests/Editor.meta
new file mode 100644
index 00000000..89790e17
--- /dev/null
+++ b/unity/org.gamecult.geometry/Tests/Editor.meta
@@ -0,0 +1,8 @@
+fileFormatVersion: 2
+guid: 3aa2de1207ba4593a6927bed95bdfea0
+folderAsset: yes
+DefaultImporter:
+  externalObjects: {}
+  userData:
+  assetBundleName:
+  assetBundleVariant:
diff --git a/unity/org.gamecult.geometry/Tests/Editor/GameCult.Geometry.Tests.Editor.asmdef b/unity/org.gamecult.geometry/Tests/Editor/GameCult.Geometry.Tests.Editor.asmdef
new file mode 100644
index 00000000..817ba8f6
--- /dev/null
+++ b/unity/org.gamecult.geometry/Tests/Editor/GameCult.Geometry.Tests.Editor.asmdef
@@ -0,0 +1,19 @@
+{
+  "name": "GameCult.Geometry.Tests.Editor",
+  "rootNamespace": "GameCult.Geometry.Tests.Editor",
+  "references": [
+    "CultMath",
+    "GameCult.Geometry",
+    "GameCult.Geometry.Unity"
+  ],
+  "includePlatforms": ["Editor"],
+  "excludePlatforms": [],
+  "allowUnsafeCode": false,
+  "overrideReferences": false,
+  "precompiledReferences": [],
+  "autoReferenced": false,
+  "defineConstraints": [],
+  "versionDefines": [],
+  "noEngineReferences": false,
+  "optionalUnityReferences": ["TestAssemblies"]
+}
diff --git a/unity/org.gamecult.geometry/Tests/Editor/GameCult.Geometry.Tests.Editor.asmdef.meta b/unity/org.gamecult.geometry/Tests/Editor/GameCult.Geometry.Tests.Editor.asmdef.meta
new file mode 100644
index 00000000..7d75ac20
--- /dev/null
+++ b/unity/org.gamecult.geometry/Tests/Editor/GameCult.Geometry.Tests.Editor.asmdef.meta
@@ -0,0 +1,7 @@
+fileFormatVersion: 2
+guid: 73e8e3a82a3441ec9f2a0f668c90f5b5
+AssemblyDefinitionImporter:
+  externalObjects: {}
+  userData:
+  assetBundleName:
+  assetBundleVariant:
diff --git a/unity/org.gamecult.geometry/Tests/Editor/GeometryPackageTests.cs b/unity/org.gamecult.geometry/Tests/Editor/GeometryPackageTests.cs
new file mode 100644
index 00000000..dec669a7
--- /dev/null
+++ b/unity/org.gamecult.geometry/Tests/Editor/GeometryPackageTests.cs
@@ -0,0 +1,54 @@
+using CultMath;
+using GameCult.Geometry.Unity;
+using NUnit.Framework;
+using UnityEngine;
+
+namespace GameCult.Geometry.Tests.Editor
+{
+    public sealed class GeometryPackageTests
+    {
+        [Test]
+        public void CultMathPrimitivesAreVisible()
+        {
+            var value = new float3(2f, 3f, 4f);
+
+            Assert.That(value.x, Is.EqualTo(2f));
+            Assert.That(value.y, Is.EqualTo(3f));
+            Assert.That(value.z, Is.EqualTo(4f));
+        }
+
+        [Test]
+        public void CoreGeometryTypesUseCultMathPrimitives()
+        {
+            var sphere = new CultSphere(new float3(1f, 2f, 3f), 4f);
+
+            Assert.That(sphere.Center, Is.EqualTo(new float3(1f, 2f, 3f)));
+            Assert.That(sphere.Radius, Is.EqualTo(4f));
+            Assert.That(sphere.Contains(new float3(1f, 2f, 7f)), Is.True);
+        }
+
+        [Test]
+        public void PlanetaryAdapterCreatesUnityMesh()
+        {
+            var mesh = PlanetaryPatchMeshAdapter.CreateFaceMesh(
+                PlanetaryCubeFace.PositiveZ,
+                2,
+                3f);
+
+            try
+            {
+                Assert.That(mesh, Is.Not.Null);
+                Assert.That(mesh.name, Does.Contain("PositiveZ"));
+                Assert.That(mesh.vertexCount, Is.EqualTo(9));
+                Assert.That(mesh.normals.Length, Is.EqualTo(9));
+                Assert.That(mesh.uv.Length, Is.EqualTo(9));
+                Assert.That(mesh.triangles.Length, Is.EqualTo(24));
+                Assert.That(mesh.bounds.size.sqrMagnitude, Is.GreaterThan(0f));
+            }
+            finally
+            {
+                Object.DestroyImmediate(mesh);
+            }
+        }
+    }
+}
diff --git a/unity/org.gamecult.geometry/Tests/Editor/GeometryPackageTests.cs.meta b/unity/org.gamecult.geometry/Tests/Editor/GeometryPackageTests.cs.meta
new file mode 100644
index 00000000..89858d8d
--- /dev/null
+++ b/unity/org.gamecult.geometry/Tests/Editor/GeometryPackageTests.cs.meta
@@ -0,0 +1,11 @@
+fileFormatVersion: 2
+guid: cc0a7b5b20004c72b9c9395d3c73360c
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData:
+  assetBundleName:
+  assetBundleVariant: