Spring Integration Resequencer Bug

TestResequencer.java

import static org.junit.Assert.assertNotNull;

import java.util.Comparator;

import org.junit.Before;
import org.junit.Test;
import org.springframework.integration.Message;
import org.springframework.integration.MessageChannel;
import org.springframework.integration.aggregator.ResequencingMessageGroupProcessor;
import org.springframework.integration.aggregator.ResequencingMessageHandler;
import org.springframework.integration.channel.QueueChannel;
import org.springframework.integration.store.MessageGroupStore;
import org.springframework.integration.store.SimpleMessageStore;
import org.springframework.integration.support.MessageBuilder;



public class TestResequencer {

    private ResequencingMessageHandler resequencer;

    private ResequencingMessageGroupProcessor processor = new ResequencingMessageGroupProcessor();

    private MessageGroupStore store = new SimpleMessageStore();

    @Before
    public void configureResequencer() {
        this.resequencer = new ResequencingMessageHandler(processor, store, null, null);
    }

    @Test
    public void testBasicResequencingWithCustomComparator() throws InterruptedException {
        this.processor.setComparator(new Comparator<Message<?>>() {
            @SuppressWarnings({ "unchecked", "rawtypes" })
            public int compare(Message<?> o1, Message<?> o2) {
                return ((Comparable)o1.getPayload()).compareTo(o2.getPayload());
            }
        });
        QueueChannel replyChannel = new QueueChannel();
        // swap payload of message (1 and 2) or (2 and 3) and the test will fail
        Message<?> message1 = createMessage("a", "ABC", 3, 1, replyChannel);
        Message<?> message2 = createMessage("b", "ABC", 3, 2, replyChannel);
        Message<?> message3 = createMessage("c", "ABC", 3, 3, replyChannel);

        this.resequencer.handleMessage(message1);
        this.resequencer.handleMessage(message2);
        this.resequencer.handleMessage(message3);

        Message<?> reply1 = replyChannel.receive(0);
        Message<?> reply2 = replyChannel.receive(0);
        Message<?> reply3 = replyChannel.receive(0);


        assertNotNull(reply1);
        // reply 2 will be null if messages are swapped as described above
        assertNotNull(reply2);
        assertNotNull(reply3);

    }


    private static Message<?> createMessage(String payload, Object correlationId, int sequenceSize, int sequenceNumber,
            MessageChannel replyChannel) {
        return MessageBuilder.withPayload(payload).setCorrelationId(correlationId).setSequenceSize(sequenceSize)
                .setSequenceNumber(sequenceNumber).setReplyChannel(replyChannel).build();
    }


}