Brad Pitt & Angelina Jolie "together and very happy,"

Kosinski, comes of the heels of Star Magazine's Brad Pitt and Angelina Jolie breakup story.

Sources tell Star that Brad Pitt and Angelina Jolie are cracking under the strain in their three-year relationship and they'll view their upcoming time apart as a trial separation of sorts.

Angelina, 31, is heading off to Prague to work on her new action thriller, Wanted, while Brad, 43, is staying behind in L.A. "This is going to be a trial separation for them," a source tells Star. "They have so many serious issues between them, that giving each other this space might allow them to step back, think about what they mean to each other and decide where they want to go in the future."

"Brad is forcing himself to go with the flow, but he must be very frustrated," reports a source. "He can't keep up with Angelina, who keeps changing things around.

"They'll sit down and agree on things, but then she'll just do something else! Like taking on this film just a few weeks after adopting her new Vietnamese son, Pax. She promised that she was going to be a stay-at-home mother, and then she changed it up."

"This really is a test for them," a friend tells Star.