Fix readonly to const transformation for string types

- Updated regex pattern on line 127 to include 'const' in the replacement string
- This ensures that both 'readonly' and 'const' C# keywords are converted to 'const' in C++
- Added test cases in experiments/ folder to verify the transformation works correctly
- All existing tests continue to pass

Resolves issue #56

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: konard

csharp/Platform.RegularExpressions.Transformer.CSharpToCpp/CSharpToCppTransformer.cs

@@ -124,7 +124,7 @@ public class CSharpToCppTransformer : TextTransformer
             (new Regex(@"(?<access>(private|protected|public): )?static readonly (?<type>[a-zA-Z0-9]+(<[a-zA-Z0-9]+>)?) (?<name>[a-zA-Z0-9_]+) = new \k<type>\((?<arguments>[^\n]+)\);"), "${access}inline static ${type} ${name} = ${type}(${arguments});", 0),
             // public: static readonly string ExceptionContentsSeparator = "---";
             // public: inline static std::string ExceptionContentsSeparator = "---";
-            (new Regex(@"(?<access>(private|protected|public): )?(const|static readonly) string (?<name>[a-zA-Z0-9_]+) = ""(?<string>(\\""|[^""\r\n])+)"";"), "${access}inline static std::string ${name} = \"${string}\";", 0),
+            (new Regex(@"(?<access>(private|protected|public): )?(const|static readonly) string (?<name>[a-zA-Z0-9_]+) = ""(?<string>(\\""|[^""\r\n])+)"";"), "${access}inline static const std::string ${name} = \"${string}\";", 0),
             // private: const int MaxPath = 92;
             // private: inline static const int MaxPath = 92;
             (new Regex(@"(?<access>(private|protected|public): )?(const|static readonly) (?<type>[a-zA-Z0-9]+) (?<name>[_a-zA-Z0-9]+) = (?<value>[^;\r\n]+);"), "${access}inline static const ${type} ${name} = ${value};", 0),

experiments/Program.cs

@@ -0,0 +1,34 @@
+using System;
+using System.IO;
+using Platform.RegularExpressions.Transformer.CSharpToCpp;
+
+class Program
+{
+    static void Main()
+    {
+        string inputCode = @"// Test cases for readonly transformations
+public class TestClass
+{
+    // Test string readonly
+    public static readonly string ExceptionContentsSeparator = ""---"";
+    private static readonly string PrivateMessage = ""error"";
+    
+    // Test other types readonly
+    public static readonly int MaxPath = 92;
+    private static readonly bool IsEnabled = true;
+    
+    // Test const (should already work)
+    private const int ConstValue = 42;
+    public const string ConstString = ""test"";
+}";
+        
+        Console.WriteLine("Original code:");
+        Console.WriteLine(inputCode);
+        Console.WriteLine("\n" + new string('=', 50) + "\n");
+        
+        var transformer = new CSharpToCppTransformer();
+        string transformed = transformer.Transform(inputCode);
+        Console.WriteLine("Transformed code:");
+        Console.WriteLine(transformed);
+    }
+}

experiments/TestTransformations.csproj

@@ -0,0 +1,9 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net8</TargetFramework>
+  </PropertyGroup>
+  <ItemGroup>
+    <ProjectReference Include="../csharp/Platform.RegularExpressions.Transformer.CSharpToCpp/Platform.RegularExpressions.Transformer.CSharpToCpp.csproj" />
+  </ItemGroup>
+</Project>

experiments/readonly_test.cs

@@ -0,0 +1,15 @@
+// Test cases for readonly transformations
+public class TestClass
+{
+    // Test string readonly
+    public static readonly string ExceptionContentsSeparator = "---";
+    private static readonly string PrivateMessage = "error";
+    
+    // Test other types readonly
+    public static readonly int MaxPath = 92;
+    private static readonly bool IsEnabled = true;
+    
+    // Test const (should already work)
+    private const int ConstValue = 42;
+    public const string ConstString = "test";
+}