const string rmdStringSource = "**hello**";
  const string rbbStringSource = "[-b]hello[/-b]";

  var rmdLexer = new RsdnMarkdownLexer();
  var rbbLexer = new RsdnBbCodeLexer();

  var rmdTree = Parser.Parse(rmdLexer, rmdStringSource);
  var rbbTree = Parser.Parse(rbbLexer, rbbStringSource);