@Test
public void testFoldLeft() {

  List<String> inputs = new ArrayList<String>();
  inputs.add("a");
  inputs.add("b");
  inputs.add("c");
  String stringified = Lists.foldLeft(new StringBuilder(), inputs,
      new Lists.Aggregator<String, StringBuilder>() {
        @Override
        public StringBuilder eval(String in, StringBuilder out) {
          if (0 != out.length()) {
            out.append(",");
          }
          out.append(in);
          return out;
        }
      }).toString();
  assertEquals("a,b,c", stringified);
}