Justin Bieber Takes DNA Test To Prove The Baby Isn't His

We've learned ... Justin took the test at a lab under "very controlled circumstances." We're told there is a solid chain of custody, so it's going to be hard for Mariah Yeater or her lawyer to challenge it.

As we first reported, Justin's team will NOT settle or even discuss settlement with Yeater or her lawyer. It's now up to her to provide DNA results from Mariah's baby.

Justin has vowed to sue Mariah and her lawyers once he establishes he's not the daddy.