how does O'brien test julia and winston?

O'Brien answers Winston's questions, explaining that Goldstein is real and that the Brotherhood (the anti-Party movement) exists. He then asks Winston and Julia what they are willing to do for the cause. They claim that they are willing to do anything, including murdering innocents and committing suicide, to further the Brotherhood. The only thing that they are unwilling to do is to part and never see each other again. O'Brien sends Martin to the pantry and begins to lecture Winston and Julia, explaining to them that they must obey him no matter what his instructions, and that he must effectively keep them in the dark about the extent of the underground organization so as to keep other members safe from discovery. Once the Thought Police find them, the Brotherhood will abandon Winston and Julia to protect the cause. Winston and Julia watch O'Brien with a sense of wonder and deep respect, and Winston believes that O'Brien represents hope for mankind. Before sending Julia out, O'Brien calls for a toast. Winston offers, "To the past," and they drink. Julia leaves, and O'Brien and Winston begin to speak of logistics. Winston reveals his "hiding place," Mr. Charrington's shop, and O'Brien tells him he will send him a copy of "the book...Goldstein's book." One day in the near future, Winston will find a misprint on an assignment and will have to ask for a repeat. The next day, he is to leave his briefcase at home. At some point during the day a man will walk up to him saying, "I believe you dropped your briefcase," and give him a briefcase containing the book. Before Winston and O'Brien part, O'Brien again offers a toast, saying "We shall meet again - if we do not meet again..." Winston interrupts hesitantly, stating, "We shall meet in the place of no darkness?" O'Brien agrees. Asked if he has any more questions before he leaves, Winston questions O'Brien about the rhyme Mr. Charrington taught him. O'Brien reveals the rest of the poem, adding, "When I grow rich, say the bells of Shoreditch." The poem is complete. The men shake hands, and Winston leaves.