Do you have loads of data? If not just use imp/exp unless you test database has to be exactly the same the production...?
Here we have three databases as well, one production one pre-production and one development. Exp/Imp works very good for me. Basically I *syncronize* the pre-production and development with production once a week...

If you have lots of data and you need the testing database exactly the same as production you probably better go for standard replication which replicate one way only