Hi Natraj,
JRebel does not have any special integrations for JUnit testing. JRebel would be somewhat useful for keep-alive testing but currently does not support it out of the box. There exist some third party solutions that aim to do this:
1) https://github.com/Tradeshift/junit-remote
2) http://arquillian.org/modules/jrebel-extension/
Hope this helps,
Risto