For Gods sake wear a suit and look smart.
At my final interview I was the ONLY one to wear a suit, and strangely enough the only one to get a job!
There was a Greek guy wearing baggy trousers and a t-shirt and some others wearing jeans and open neck shirts.
Put it this way; wearing a suit won't get you the job - not wearing a suit can contribute to not getting it.
Its your one chance to make an impression, dont waste it -and despite what some might say/what impression might be given looking smart at the tests/interviews is important.