test(backend): add xUnit tests for the API skeleton

Add tests/TarninaHub.Tests with health controller and SurrealDB endpoint builder tests, and register the test and layer projects in the solution.

TarninaHub.slnx

@@ -1,5 +1,11 @@
 <Solution>
   <Folder Name="/backend/">
     <Project Path="backend/TarninaHub.csproj" />
+    <Project Path="backend/Application/TarninaHub.Application.csproj" />
+    <Project Path="backend/Domain/TarninaHub.Domain.csproj" />
+    <Project Path="backend/Infrastructure/TarninaHub.Infrastructure.csproj" />
+  </Folder>
+  <Folder Name="/tests/">
+    <Project Path="tests/TarninaHub.Tests/TarninaHub.Tests.csproj" />
   </Folder>
 </Solution>

tests/TarninaHub.Tests/Controllers/HealthControllerTests.cs

@@ -0,0 +1,19 @@
+using Microsoft.AspNetCore.Mvc;
+using TarninaHub.Controllers;
+
+namespace TarninaHub.Tests.Controllers;
+
+public class HealthControllerTests
+{
+    [Fact]
+    public void Get_ReturnsOkWithHealthyStatus()
+    {
+        var controller = new HealthController();
+
+        var result = controller.Get();
+
+        var ok = Assert.IsType<OkObjectResult>(result.Result);
+        var payload = Assert.IsType<HealthResponse>(ok.Value);
+        Assert.Equal("ok", payload.Status);
+    }
+}

tests/TarninaHub.Tests/Infrastructure/SurrealDbEndpointTests.cs

@@ -0,0 +1,34 @@
+using TarninaHub.Infrastructure.Settings;
+
+namespace TarninaHub.Tests.Infrastructure;
+
+public class SurrealDbEndpointTests
+{
+    [Fact]
+    public void Build_ReturnsRemoteUrl_WhenConfigured()
+    {
+        var settings = new SurrealDbSettings
+        {
+            RemoteUrl = "ws://127.0.0.1:8010/rpc",
+        };
+
+        var endpoint = SurrealDbEndpoint.Build(settings);
+
+        Assert.Equal("ws://127.0.0.1:8010/rpc", endpoint);
+    }
+
+    [Fact]
+    public void Build_ReturnsRocksDbEndpoint_WithForwardSlashes_WhenEmbedded()
+    {
+        var settings = new SurrealDbSettings
+        {
+            DataDirectory = "data",
+        };
+
+        var endpoint = SurrealDbEndpoint.Build(settings);
+
+        Assert.StartsWith("rocksdb://", endpoint);
+        Assert.DoesNotContain('\\', endpoint);
+        Assert.EndsWith("/data", endpoint);
+    }
+}

tests/TarninaHub.Tests/TarninaHub.Tests.csproj

@@ -0,0 +1,26 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="coverlet.collector" Version="6.0.4" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
+    <PackageReference Include="xunit" Version="2.9.3" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="3.1.4" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Using Include="Xunit" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\backend\TarninaHub.csproj" />
+    <ProjectReference Include="..\..\backend\Infrastructure\TarninaHub.Infrastructure.csproj" />
+  </ItemGroup>
+
+</Project>