A lot of companies have stopped doing these…the results are quite often nonsense.
When I was working for a company as a placement for a year during my degree they used all the student workers (about 30 of us) to try out a consultancy offering these testing.
We then got the results from the tester…apparently I have no ambition and I’m not interested in succeeding. I laughed and asked what he thought I was spending 4 years of my life studying towards a degree for if I had no ambition.
One of the other students was told he wasn’t a physically active individual and wasn’t a team player. This was someone who played Saturday and Sunday league football, and had organised the football team for all the students working at the company.
The HR manager wasn’t shy in telling people that the results were rubbish and they weren’t going to bother with the tests in the future.
I wouldn’t worry too much about it…although they apparently can tell if you’ve tried to ‘beat the test’.
And to answer your question…wear a suit.