Scribe2

public class Scribe2
{
    private IWrapFile fileService;

    public Scribe2(IWrapFile file)
    {
        fileService = file;
    }

    public void SaveMessage(string file, string data)
    {
        if (fileService.Exists(file))  // Now uses the injected IWrapFile service
        {
            throw new Exception("File name must be unique");
        }

        fileService.WriteAllText(file, data);
    }
}