Another technique I've used successfully is to put both jars on the classpatch and use a <bridge/> to connect them.
For example, if app1 ends with
and app2 begins with
Structure your files such that the adapters can be skipped (e.g. using Spring 3.1 profiles, or putting them in a separate config file that is <import/>ed into the production code).
Then, in your test case create a <bridge input-channel="lastChanApp1" outputChannel="firstChanApp2" />
If you are using gateways you can bridge the reply channels too.
There are some limitations with this technique, but it works in many cases.
Gary P. Russell
Spring Integration Team
SpringSource, a division of VMware