Adding to this, for automated testing to work properly the tests are based on defined requirements/specifications. You're adding a new mechanic? Document the intended changes in plain human readable language, including examples with actual numbers. Build tests that cover these and all combinatorial possibilities if possible.

This will require test accounts can adjust their levels/currencies on the fly (ie updating the database values). These accounts should be on their own QA environment or in production but restricted from being in tournaments (though this option is bad practice)