Just have to add something here, because I had a similar problem. The problem described in http://jira.jboss.com/jira/browse/EMB-8 applies, if nothing is logged to log4j at all.
If log4j is used for logging, but your configuration is not picked up (in your case you don't see the hibernate debug output), then there is some other configuration that is picked up before your log4j.xml. Have a look at the path used when you run the tests. It could also be an orphan log4j.properties.
In my case it worked, when I put bootstrap at the very beginning of the classpath.