checkNotNull(factory);
    return new CharSourceFactory() {
      @Override
      public CharSource createSource(String string) throws IOException {
        return factory.createSource(string.getBytes(Charsets.UTF_8)).asCharSource(Charsets.UTF_8);
      }

      @Override
      public String getExpected(String data) {
        return new String(factory.getExpected(data.getBytes(Charsets.UTF_8)), Charsets.UTF_8);
      }

    checkNotNull(factory);
    return new CharSourceFactory() {
      @Override
      public CharSource createSource(String string) throws IOException {
        return factory.createSource(string.getBytes(Charsets.UTF_8)).asCharSource(Charsets.UTF_8);
      }

      @Override
      public String getExpected(String data) {
        return new String(factory.getExpected(data.getBytes(Charsets.UTF_8)), Charsets.UTF_8);
      }