ByteArrayOutputStream out = new ByteArrayOutputStream();
handler.write(new DataOutputStream(out));
MasterAggregatorHandler restartedHandler =
new MasterAggregatorHandler(conf, progressable);
restartedHandler.readFields(
new DataInputStream(new ByteArrayInputStream(out.toByteArray())));
assertEquals(2, getAggregatorMap(restartedHandler).size());
AggregatorWrapper<Writable> regularAgg =