Add lightweight architecture testing sample

.github/workflows/build-samples.yml

@@ -7,13 +7,15 @@ on:
       - "dotnet-ai/provider-agnostic-chat-gateway/**"
       - "dotnet-ai/hybrid-search-ef-core-pgvector/**"
       - "dotnet-aspire/orchestrate-distributed-system/**"
+      - "software-architecture/architecture-testing-dotnet/**"
       - ".github/workflows/build-samples.yml"
 
   pull_request:
     paths:
       - "dotnet-ai/provider-agnostic-chat-gateway/**"
       - "dotnet-ai/hybrid-search-ef-core-pgvector/**"
       - "dotnet-aspire/orchestrate-distributed-system/**"
+      - "software-architecture/architecture-testing-dotnet/**"
       - ".github/workflows/build-samples.yml"
 
   workflow_dispatch:
@@ -103,3 +105,35 @@ jobs:
             dotnet-aspire/orchestrate-distributed-system/AspireOrchestrationMinimal.slnx \
             --configuration Release \
             --no-restore
+
+  test-architecture-rules:
+    name: Test architecture rules
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Check out repository
+        uses: actions/checkout@v5
+
+      - name: Install .NET 10 SDK
+        uses: actions/setup-dotnet@v5
+        with:
+          dotnet-version: "10.0.x"
+
+      - name: Restore
+        run: |
+          dotnet restore \
+            software-architecture/architecture-testing-dotnet/ArchitectureGuardMinimal.slnx
+
+      - name: Build
+        run: |
+          dotnet build \
+            software-architecture/architecture-testing-dotnet/ArchitectureGuardMinimal.slnx \
+            --configuration Release \
+            --no-restore
+
+      - name: Test architecture rules
+        run: |
+          dotnet test \
+            software-architecture/architecture-testing-dotnet/tests/ArchitectureGuard.ArchitectureTests/ArchitectureGuard.ArchitectureTests.csproj \
+            --configuration Release \
+            --no-build

README.md

@@ -12,6 +12,7 @@ Each sample folder contains a focused implementation of one tutorial topic. The
 | [`dotnet-ai/provider-agnostic-chat-gateway`](dotnet-ai/provider-agnostic-chat-gateway/) | One HTTP chat endpoint using Ollama and optional OpenAI providers through `Microsoft.Extensions.AI.IChatClient` | [Build a switchable multi-provider AI gateway with IChatClient](https://www.dotnet-guide.com/tutorials/dotnet-ai/provider-agnostic-chat-gateway/) |
 | [`dotnet-ai/hybrid-search-ef-core-pgvector`](dotnet-ai/hybrid-search-ef-core-pgvector/) | Minimal Reciprocal Rank Fusion demo combining pre-ranked keyword and vector results | [Hybrid Search in .NET with EF Core 10 and pgvector](https://www.dotnet-guide.com/tutorials/dotnet-ai/hybrid-search-ef-core-pgvector/) |
 | [`dotnet-aspire/orchestrate-distributed-system`](dotnet-aspire/orchestrate-distributed-system/) | Minimal Aspire AppHost coordinating a web project and API with service discovery and startup ordering | [Aspire in .NET: Orchestrate, Run, and Deploy a Distributed System from One App Host](https://www.dotnet-guide.com/tutorials/dotnet-aspire/orchestrate-distributed-system/) |
+| [`software-architecture/architecture-testing-dotnet`](software-architecture/architecture-testing-dotnet/) | Minimal NetArchTest.eNhancedEdition rule that prevents Domain from depending on outer layers | [Architecture Testing in .NET: Enforce Layer and Module Boundaries with NetArchTest and ArchUnitNET](https://www.dotnet-guide.com/tutorials/software-architecture/architecture-testing-dotnet/) |
 
 ## Companion articles
 
@@ -68,6 +69,27 @@ tutorials/
 |       `-- AspireOrchestrationMinimal.Web/
 |           |-- Program.cs
 |           `-- AspireOrchestrationMinimal.Web.csproj
+|-- software-architecture/
+|   `-- architecture-testing-dotnet/
+|       |-- ArchitectureGuardMinimal.slnx
+|       |-- README.md
+|       |-- src/
+|       |   |-- ArchitectureGuard.Domain/
+|       |   |   |-- ArchitectureGuard.Domain.csproj
+|       |   |   |-- DomainAssemblyMarker.cs
+|       |   |   `-- Order.cs
+|       |   |-- ArchitectureGuard.Application/
+|       |   |   |-- ArchitectureGuard.Application.csproj
+|       |   |   |-- ApplicationAssemblyMarker.cs
+|       |   |   `-- GetOrderSummary.cs
+|       |   `-- ArchitectureGuard.Infrastructure/
+|       |       |-- ArchitectureGuard.Infrastructure.csproj
+|       |       |-- InfrastructureAssemblyMarker.cs
+|       |       `-- InMemoryOrderRepository.cs
+|       `-- tests/
+|           `-- ArchitectureGuard.ArchitectureTests/
+|               |-- ArchitectureGuard.ArchitectureTests.csproj
+|               `-- LayerRules.cs
 |-- .github/
 |   `-- workflows/
 |       `-- build-samples.yml

software-architecture/architecture-testing-dotnet/ArchitectureGuardMinimal.slnx

@@ -0,0 +1,6 @@
+<Solution>
+  <Project Path="src/ArchitectureGuard.Domain/ArchitectureGuard.Domain.csproj" />
+  <Project Path="src/ArchitectureGuard.Application/ArchitectureGuard.Application.csproj" />
+  <Project Path="src/ArchitectureGuard.Infrastructure/ArchitectureGuard.Infrastructure.csproj" />
+  <Project Path="tests/ArchitectureGuard.ArchitectureTests/ArchitectureGuard.ArchitectureTests.csproj" />
+</Solution>

software-architecture/architecture-testing-dotnet/README.md

@@ -0,0 +1,199 @@
+# Architecture Testing in .NET — Minimal Layer Rule
+
+A minimal .NET 10 architecture-testing sample demonstrating how a dedicated
+test project inspects compiled assemblies and fails the build when a forbidden
+dependency appears.
+
+## Full tutorial
+
+[Architecture Testing in .NET: Enforce Layer and Module Boundaries with NetArchTest and ArchUnitNET](https://www.dotnet-guide.com/tutorials/software-architecture/architecture-testing-dotnet/)
+
+## What this sample demonstrates
+
+* a layered .NET 10 solution with Domain, Application, and Infrastructure projects;
+* an architecture-test project using **NetArchTest.eNhancedEdition**;
+* typed assembly markers that give the test project a reliable way to locate each assembly;
+* one forbidden-dependency rule that prevents Domain from depending on outer layers;
+* selector non-empty protection so the rule cannot silently pass when no types are found;
+* readable failure output naming the protected rule and the offending types;
+* normal `dotnet test` execution through xUnit v3.
+
+## Architecture
+
+```text
+Infrastructure ──► Application ──► Domain
+
+Allowed direction: toward Domain (outer → inner)
+Rejected direction: Domain toward outer layers
+```
+
+```text
+ArchitectureTests
+     │
+     ├── inspects Domain
+     ├── inspects Application
+     └── inspects Infrastructure
+```
+
+## File structure
+
+```text
+architecture-testing-dotnet/
+├── ArchitectureGuardMinimal.slnx
+├── README.md
+├── src/
+│   ├── ArchitectureGuard.Domain/
+│   │   ├── ArchitectureGuard.Domain.csproj
+│   │   ├── DomainAssemblyMarker.cs
+│   │   └── Order.cs
+│   ├── ArchitectureGuard.Application/
+│   │   ├── ArchitectureGuard.Application.csproj
+│   │   ├── ApplicationAssemblyMarker.cs
+│   │   └── GetOrderSummary.cs
+│   └── ArchitectureGuard.Infrastructure/
+│       ├── ArchitectureGuard.Infrastructure.csproj
+│       ├── InfrastructureAssemblyMarker.cs
+│       └── InMemoryOrderRepository.cs
+└── tests/
+    └── ArchitectureGuard.ArchitectureTests/
+        ├── ArchitectureGuard.ArchitectureTests.csproj
+        └── LayerRules.cs
+```
+
+## Prerequisites
+
+* .NET 10 SDK
+
+No Docker, Podman, databases, API keys, or cloud credentials are required.
+
+## Run the sample
+
+Open a terminal in this sample folder and run:
+
+```powershell
+dotnet restore
+dotnet build --configuration Release --no-restore
+dotnet test --configuration Release --no-build
+```
+
+Expected output:
+
+```text
+Passed! - Failed: 0, Passed: 1, Skipped: 0, Total: 1
+```
+
+## Prove the rule works
+
+To verify that the architecture test genuinely enforces layer boundaries,
+temporarily add a forbidden dependency:
+
+1. Add an Infrastructure project reference to Domain:
+   ```powershell
+   dotnet add src/ArchitectureGuard.Domain/ArchitectureGuard.Domain.csproj reference src/ArchitectureGuard.Infrastructure/ArchitectureGuard.Infrastructure.csproj
+   ```
+
+2. Edit `src/ArchitectureGuard.Domain/Order.cs` to reference an outer type:
+   ```csharp
+   // Temporary violation — add this using:
+   using ArchitectureGuard.Infrastructure;
+
+   namespace ArchitectureGuard.Domain;
+
+   public sealed record Order(Guid Id, decimal Total)
+   {
+       // Add a temporary field that references the outer layer:
+       private static readonly InfrastructureAssemblyMarker _marker = new();
+   }
+   ```
+
+3. Run the tests again:
+   ```powershell
+   dotnet build --configuration Release --no-restore
+   dotnet test --configuration Release --no-build
+   ```
+
+   The architecture test now fails with a message like:
+   ```text
+   Architecture rule failed: Domain must remain independent of outer layers.
+    - ArchitectureGuard.Domain.Order
+      [dependency explanation]
+   ```
+
+4. Remove the temporary violation:
+   ```powershell
+   dotnet remove src/ArchitectureGuard.Domain/ArchitectureGuard.Domain.csproj reference src/ArchitectureGuard.Infrastructure/ArchitectureGuard.Infrastructure.csproj
+   ```
+   Then revert `Order.cs` to its original content.
+
+5. Rebuild and confirm the test passes again.
+
+Do **not** commit the violation.
+
+## Project references
+
+```text
+ArchitectureGuard.Application
+└── references ArchitectureGuard.Domain
+
+ArchitectureGuard.Infrastructure
+├── references ArchitectureGuard.Application
+└── references ArchitectureGuard.Domain
+
+ArchitectureGuard.ArchitectureTests
+├── references ArchitectureGuard.Domain
+├── references ArchitectureGuard.Application
+└── references ArchitectureGuard.Infrastructure
+```
+
+Domain references nothing.
+
+## Important boundary
+
+This repository sample intentionally does **not** reproduce the complete tutorial.
+The full DOTNET GUIDE tutorial additionally contains:
+
+* ArchUnitNET;
+* Roslyn analyzer projects;
+* `Microsoft.CodeAnalysis.CSharp`;
+* custom analyzer packaging;
+* analyzer unit tests;
+* modular-monolith slicing (Orders and Billing modules);
+* contracts assemblies;
+* reflection-based endpoint authorization checks;
+* naming and sealing convention suites;
+* value-object immutability rules;
+* legacy violation baselines;
+* multiple architecture-test frameworks;
+* a web API project;
+* controllers or Minimal API endpoints;
+* EF Core;
+* databases;
+* authentication;
+* containers;
+* cloud services;
+* production deployment;
+* extensive performance optimization;
+* complete production-readiness policy.
+
+## Verification
+
+| Item | Detail |
+| --- | --- |
+| Target framework | .NET 10 (`net10.0`) |
+| SDK | .NET SDK 10.0.302 |
+| Architecture library | `NetArchTest.eNhancedEdition` 1.4.5 |
+| Test framework | `xunit.v3` 3.2.2 |
+| Test runner | `xunit.runner.visualstudio` 3.1.5 |
+| Test SDK | `Microsoft.NET.Test.Sdk` 17.14.1 |
+| External services required | None |
+| Containers required | None |
+| API keys required | None |
+| Release build | Verified |
+| Architecture test | Verified |
+| Last reviewed | 2026-07-27 |
+
+## License
+
+Repository-owned sample code is available under the [MIT License](../../LICENSE).
+
+Third-party NetArchTest and xUnit packages remain subject to their own licenses.

software-architecture/architecture-testing-dotnet/src/ArchitectureGuard.Application/ApplicationAssemblyMarker.cs

@@ -0,0 +1,3 @@
+namespace ArchitectureGuard.Application;
+
+public sealed class ApplicationAssemblyMarker;

software-architecture/architecture-testing-dotnet/src/ArchitectureGuard.Application/ArchitectureGuard.Application.csproj

@@ -0,0 +1,13 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <ItemGroup>
+    <ProjectReference Include="..\ArchitectureGuard.Domain\ArchitectureGuard.Domain.csproj" />
+  </ItemGroup>
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

software-architecture/architecture-testing-dotnet/src/ArchitectureGuard.Application/GetOrderSummary.cs

@@ -0,0 +1,3 @@
+namespace ArchitectureGuard.Application;
+
+public sealed record GetOrderSummary(Guid OrderId);

software-architecture/architecture-testing-dotnet/src/ArchitectureGuard.Domain/ArchitectureGuard.Domain.csproj

@@ -0,0 +1,9 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

software-architecture/architecture-testing-dotnet/src/ArchitectureGuard.Domain/DomainAssemblyMarker.cs

@@ -0,0 +1,3 @@
+namespace ArchitectureGuard.Domain;
+
+public sealed class DomainAssemblyMarker;

software-architecture/architecture-testing-dotnet/src/ArchitectureGuard.Domain/Order.cs

@@ -0,0 +1,3 @@
+namespace ArchitectureGuard.Domain;
+
+public sealed record Order(Guid Id, decimal Total);

software-architecture/architecture-testing-dotnet/src/ArchitectureGuard.Infrastructure/ArchitectureGuard.Infrastructure.csproj

@@ -0,0 +1,14 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <ItemGroup>
+    <ProjectReference Include="..\ArchitectureGuard.Application\ArchitectureGuard.Application.csproj" />
+    <ProjectReference Include="..\ArchitectureGuard.Domain\ArchitectureGuard.Domain.csproj" />
+  </ItemGroup>
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

software-architecture/architecture-testing-dotnet/src/ArchitectureGuard.Infrastructure/InMemoryOrderRepository.cs

@@ -0,0 +1,13 @@
+using ArchitectureGuard.Application;
+using ArchitectureGuard.Domain;
+
+namespace ArchitectureGuard.Infrastructure;
+
+public sealed class InMemoryOrderRepository
+{
+    public GetOrderSummary GetSummary(Guid orderId)
+    {
+        var order = new Order(orderId, 123.45m);
+        return new GetOrderSummary(order.Id);
+    }
+}

software-architecture/architecture-testing-dotnet/src/ArchitectureGuard.Infrastructure/InfrastructureAssemblyMarker.cs

@@ -0,0 +1,3 @@
+namespace ArchitectureGuard.Infrastructure;
+
+public sealed class InfrastructureAssemblyMarker;