Is there a TEST server?

The test server comes and goes, depending on whether Three Rings wants us to test things. When the test server starts up, there will be an official announcement. It's not a secret. It's a big incentive for players to spend real money.

Not just that. Testing servers in general are used to give feedback to the developers. Just make sure you don't post any of your findings from third party software (other MMORPG's and games in general frown upon the use of them) or from the test server in any other subforum than "Testing Feedback".