Move project to sub-directory, add empty test project, and fix namespace

QuadtreeTests/QuadtreeTests.csproj

@@ -0,0 +1,28 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+
+    <IsPackable>false</IsPackable>
+    <IsTestProject>true</IsTestProject>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="coverlet.collector" Version="6.0.0" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.8.0" />
+    <PackageReference Include="NUnit" Version="3.14.0" />
+    <PackageReference Include="NUnit.Analyzers" Version="3.9.0" />
+    <PackageReference Include="NUnit3TestAdapter" Version="4.5.0" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\Quadtree\Quadtree.csproj" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Using Include="NUnit.Framework" />
+  </ItemGroup>
+
+</Project>

QuadtreeTests/Tests.cs

@@ -0,0 +1,19 @@
+using SpatialCollections;
+
+namespace QuadtreeTests
+{
+    public class Tests
+    {
+        [SetUp]
+        public void Setup()
+        {
+        }
+
+        [Test]
+        public void Test1()
+        {
+            Quadtree quadtree = new(20, 4);
+            Assert.Pass();
+        }
+    }
+}