The Tor Browser / file revision

 var Ci = Components.interfaces,

     Cc = Components.classes,

     CC = Components.Constructor;

 var converter = Cc["@mozilla.org/intl/scriptableunicodeconverter"]

                   .createInstance(Ci.nsIScriptableUnicodeConverter);

 converter.charset = "UTF-8";

 var SIS = CC("@mozilla.org/scriptableinputstream;1",

              "nsIScriptableInputStream",

              "init");

 function test_char(code) {

     dump("test_char(0x" + code.toString(16) + ")\n");

     var original = String.fromCharCode(code);

     var nativeStream = converter.convertToInputStream(original);

     var stream = new SIS(nativeStream);

     var utf8Result = stream.read(stream.available());

     stream.close();

     var result = converter.ConvertToUnicode(utf8Result);

     do_check_eq(escape(original), escape(result));

 }

 function run_test() {

     // This is not a very comprehensive test.

     for (var i = 0x007f - 2; i <= 0x007f; i++)

         test_char(i);

     for (i = 0x07ff - 2; i <= 0x07ff; i++)

         test_char(i);

     for (i = 0x1000 - 2; i <= 0x1000 + 2; i++)

         test_char(i);

     for (i = 0xe000; i <= 0xe000 + 2; i++)

         test_char(i);

 }