Add 'CSharpCodeFixTest<,>' helper type

tests/ComputeSharp.D2D1.WinUI.Tests.SourceGenerators/Helpers/CSharpCodeFixerTest{TAnalyzer,TCodeFixer}.cs

@@ -0,0 +1,40 @@
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Microsoft.CodeAnalysis.Testing;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CodeFixes;
+using Microsoft.CodeAnalysis.CSharp.Testing;
+
+#pragma warning disable IDE0290
+
+namespace ComputeSharp.Tests.SourceGenerators.Helpers;
+
+/// <summary>
+/// A custom <see cref="CSharpCodeFixTest{TAnalyzer, TCodeFix, TVerifier}"/> that uses a specific C# language version to parse code.
+/// </summary>
+/// <typeparam name="TAnalyzer">The type of the analyzer to produce diagnostics.</typeparam>
+/// <typeparam name="TCodeFixer">The type of code fix to test.</typeparam>
+internal sealed class CSharpCodeFixTest<TAnalyzer, TCodeFixer> : CSharpCodeFixTest<TAnalyzer, TCodeFixer, DefaultVerifier>
+    where TAnalyzer : DiagnosticAnalyzer, new()
+    where TCodeFixer : CodeFixProvider, new()
+{
+    /// <summary>
+    /// The C# language version to use to parse code.
+    /// </summary>
+    private readonly LanguageVersion languageVersion;
+
+    /// <summary>
+    /// Creates a new <see cref="CSharpCodeFixTest{TAnalyzer, TCodeFix}"/> instance with the specified parameters.
+    /// </summary>
+    /// <param name="languageVersion">The C# language version to use to parse code.</param>
+    public CSharpCodeFixTest(LanguageVersion languageVersion)
+    {
+        this.languageVersion = languageVersion;
+    }
+
+    /// <inheritdoc/>
+    protected override ParseOptions CreateParseOptions()
+    {
+        return new CSharpParseOptions(this.languageVersion, DocumentationMode.Diagnose);
+    }
+}