There is unstable test in HornetQ test suite:
org.hornetq.tests.integration.client.NettyConsumerWindowSizeTest.testSlowConsumerNoBuffer

Hudson job:
http://hudson.qa.jboss.com/hudson/view/EAP5/view/HornetQ/job/_hornetq-RHEL4-x86-SunJDK1.6-AIO/57/

Log:
Error Message

expected:<Msg[0]> but was:<Msg[2]>

Stacktrace

junit.framework.ComparisonFailure: expected:<Msg[0]> but was:<Msg[2]>
at org.hornetq.tests.integration.client.ConsumerWindowSizeTest.internalTestSlowConsumerNoBuffer(ConsumerWindowSizeTest.java:578)
at org.hornetq.tests.integration.client.ConsumerWindowSizeTest.testSlowConsumerNoBuffer(ConsumerWindowSizeTest.java:487)

It looks that test expects to receive all messages in the same order as they were sent and it does not happen always.