Your mapped named is 'DefaultDS', that is the resource that the container is going to bind to the resource ref you made using annotations. So the container is going to create a local resource ref with name 'test' and he is going to bind 'DefaultDS' to that local ref.
Anywhere, starting from your bean, you can now do a manual lookup of 'test' but it will always map to 'DefaultDS'. JBOSS automatically deploys an HSQL db under that JNDI name (DefuaultDS). So you are indeed getting a successful connection, but to the in memory database started by JBOSS instead of your oracle database.
You should probably supply the correct mapped name to which the oracle connection is made available under (probably 'test' if I look at your configuration at the bottom)