Adding unit test for t4 template

Author: brunolins16

eng/Dependencies.props

@@ -189,6 +189,7 @@ and are generated based on the last package release.
     <LatestPackageReference Include="MessagePackAnalyzer" />
     <LatestPackageReference Include="Microsoft.Data.SqlClient" />
     <LatestPackageReference Include="Mono.Cecil" />
+    <LatestPackageReference Include="Mono.TextTemplating" />
     <LatestPackageReference Include="Moq" />
     <LatestPackageReference Include="Newtonsoft.Json.Bson" />
     <LatestPackageReference Include="NSwag.ApiDescription.Client" />

eng/Versions.props

@@ -257,6 +257,7 @@
     <MessagePackAnalyzerVersion>$(MessagePackVersion)</MessagePackAnalyzerVersion>
     <MoqVersion>4.10.0</MoqVersion>
     <MonoCecilVersion>0.11.2</MonoCecilVersion>
+    <MonoTextTemplatingVersion>2.2.1</MonoTextTemplatingVersion>
     <NewtonsoftJsonBsonVersion>1.0.2</NewtonsoftJsonBsonVersion>
     <NewtonsoftJsonVersion>13.0.1</NewtonsoftJsonVersion>
     <NSwagApiDescriptionClientVersion>13.0.4</NSwagApiDescriptionClientVersion>

src/Http/Http.Results/Directory.Build.props

@@ -0,0 +1,7 @@
+<Project>
+  <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory)..\, Directory.Build.props))\Directory.Build.props" />
+
+  <PropertyGroup>
+    <HttpResultsSourceRoot>$(MSBuildThisFileDirectory)\src</HttpResultsSourceRoot>
+  </PropertyGroup>
+</Project>

src/Http/Http.Results/src/Microsoft.AspNetCore.Http.Results.csproj

@@ -33,4 +33,11 @@
     <Service Include="{508349b6-6b84-4df5-91f0-309beebad82d}" />
   </ItemGroup>
 
+  <ItemGroup>
+    <None Update="ResultsCache.StatusCodes.tt">
+      <Generator>TextTemplatingFileGenerator</Generator>
+      <LastGenOutput>ResultsCache.StatusCodes.cs</LastGenOutput>
+    </None>
+  </ItemGroup>
+
 </Project>

src/Http/Http.Results/test/Microsoft.AspNetCore.Http.Results.Tests.csproj

@@ -8,8 +8,12 @@
     <Reference Include="Microsoft.AspNetCore.Http" />
     <Reference Include="Microsoft.AspNetCore.Http.Results" />
     <Reference Include="Microsoft.Extensions.DependencyInjection" />
+    <Reference Include="Mono.TextTemplating" />
 
     <Compile Include="$(SharedSourceRoot)ResultsTests\*.cs" LinkBase="Shared" />
+    
+    <Content  Include="$(HttpResultsSourceRoot)\ResultsCache.StatusCodes.tt" LinkBase="Shared\GeneratedContent" CopyToOutputDirectory="PreserveNewest" />
+    <Content  Include="$(HttpResultsSourceRoot)\ResultsCache.StatusCodes.cs" LinkBase="Shared\GeneratedContent" CopyToOutputDirectory="PreserveNewest" />
   </ItemGroup>
 
 </Project>

src/Http/Http.Results/test/ResultsCacheTests.cs

@@ -0,0 +1,24 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace Microsoft.AspNetCore.Http.Results.Tests;
+
+using Mono.TextTemplating;
+
+public class ResultsCacheTests
+{
+    [Fact]
+    public void GeneratedCodeIsUpToData()
+    {
+        var currentContentPath = Path.Combine(AppContext.BaseDirectory, "shared", "GeneratedContent", "ResultsCache.StatusCodes.cs");
+        var templatePath = Path.Combine(AppContext.BaseDirectory, "shared", "GeneratedContent", "ResultsCache.StatusCodes.tt");
+
+        var generator = new TemplateGenerator();
+        var compiledTemplate = generator.CompileTemplate(File.ReadAllText(templatePath));
+
+        var generatedContent = compiledTemplate.Process();
+        var currentContent = File.ReadAllText(currentContentPath);
+
+        Assert.Equal(currentContent, generatedContent);
+    }
+}

src/Http/README.md

@@ -24,6 +24,13 @@ The following contains a description of each sub-directory in the `Http` directo
 
 ## Development Setup
 
+To run the code generation using [T4 Text Templates](https://docs.microsoft.com/en-us/visualstudio/modeling/code-generation-and-t4-text-templates), you can use an IDE that supports it (eg. Visual Studio or JetBrains Rider) or install the cross-platform open-source dotnet tool [Mono/T4](https://github.com/mono/t4).
+
+```powershell
+> dotnet tool install -g dotnet-t4
+> t4 Http.Results\ResultsCache.StatusCodes.cs
+```
+
 ### Build
 
 To build this specific project from source, follow the instructions [on building the project](../../docs/BuildFromSource.md#step-3-build-the-repo).