The 17-year-old singer was accused by 20-yeard-old Mariah Yeater of being the father of her child, after they allegedly slept together at one of his concerts last year.
The Biebs has consistently denied her claims and now he's taken the steps to get himself in the all clear.
According to RadarOnlie.com, he took the rest in New Jersey last Friday, with a source confirming the process "lasted less than ten minutes."
"It's an extremely reputable facility," said the insider, "and there are surveillance cameras everywhere to ensure tests are done with complete integrity.
"Justin's test should be completed by the end of the week. It's time for Mariah to put up or shut up, and submit the baby to a test."
Last week, Mariah appeared to have prematurely given herself up as a big fat faker, after sending texts to friends asking them to 'ERASE ALL MESSAGES' where she mentions the baby isn't Bieber's son.
The Biebs has vowed to sue Mariah and her attorneys once the results are in that he's not a teenage dad>.
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