diff --git a/lib/Frontend/RewriteTest.cpp b/lib/Frontend/RewriteTest.cpp
new file mode 100644
index 0000000..0414678
--- /dev/null
+++ b/lib/Frontend/RewriteTest.cpp
@@ -0,0 +1,39 @@
+//===--- RewriteTest.cpp - Rewriter playground ----------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This is a testbed.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Frontend/Utils.h"
+#include "clang/Lex/Preprocessor.h"
+#include "clang/Rewrite/TokenRewriter.h"
+#include "llvm/Support/raw_ostream.h"
+
+void clang::DoRewriteTest(Preprocessor &PP, llvm::raw_ostream* OS) {
+  SourceManager &SM = PP.getSourceManager();
+  const LangOptions &LangOpts = PP.getLangOptions();
+
+  TokenRewriter Rewriter(SM.getMainFileID(), SM, LangOpts);
+
+  // Throw <i> </i> tags around comments.
+  for (TokenRewriter::token_iterator I = Rewriter.token_begin(),
+       E = Rewriter.token_end(); I != E; ++I) {
+    if (I->isNot(tok::comment)) continue;
+
+    Rewriter.AddTokenBefore(I, "<i>");
+    Rewriter.AddTokenAfter(I, "</i>");
+  }
+
+
+  // Print out the output.
+  for (TokenRewriter::token_iterator I = Rewriter.token_begin(),
+       E = Rewriter.token_end(); I != E; ++I)
+    *OS << PP.getSpelling(*I);
+}