"The International Space Station may provide the setting for a 500-day pretend trip to Mars in another few years. NASA said Tuesday that consideration is under way to use the space station as a dry run for a simulated trip to and from Mars. It would be patterned after Russia's mock flight to Mars that lasted 520 days at a Moscow research center."
Let's Stop Going in Circles - And Go Somewhere (2002), SpaceRef
"Re-dedicating the International Space Station to the specific task of flight certifying humans for travel to Mars - on a fixed schedule - and then holding to that schedule would bring a long absent focus and general direction to this meritorious but meandering program."
Keith's note Its about time NASA decided to do this. I think they should have been doing this from the moment that the first crew arrived.