Here's another deal from the International Bridge Press Association's newsletter. The IBPA is a group of more than 300 bridge journalists from around the world. The newsletter, edited by Canadian John Carruthers, is a nice source of information and bridge deals such as this one. Test your defense as East:
Partner leads the ♥2. Declarer wins the ace and ruffs a heart. He lays down the ♠A and gets the bad news. An easy contract just got harder.
South continues by cashing the ♣Q, then playing the ♦A K. You ruff the second diamond -- now what?
Trick question. If you ruff, you are endplayed. If you exit with the ♣J, declarer can win the king and lead the ace. You must ruff or he has 12 tricks. Declarer overruffs, draws trumps and arranges to ruff a diamond in dummy for 12 tricks.
If you discard the ♣J on the second high diamond, you can ruff the third diamond and exit with a heart and the contract can't be made.