A company called Y Combinator is starting out tests few dozen residents in Oakland for this. It'll be interesting to see the results, particularly if they can keep expanding it into something very wide scale.
There have been tests before about giving poor people money with no strings attached, but those were about trying to make poor people productive, which in america it didn't quite work out in that way.
But if basic income doesn't care about unproductive people staying unproductive, the question should be how many people that are just making by would stop working, instead of choosing to become richer by combining the free money with the money they make in whatever mid to low class job they have.
No way would a person making $10,000 a month choose to quit working because he's getting an additional $2,000 a month for free, especially if he's paying an additional 2,000 a month in taxes to pay for the program itself, but what about someone already making $2,000 a month? And would that differ from people making $500 a month or $4,000 a month?