All Big Six publishers are expected to testify in U.S. federal court against Apple during its ebook price-fixing trial, which begins June 3.

According to a court document filed yesterday, executives from Hachette, HarperCollins, Macmillan, Random House, and Simon & Schuster will admit to conspiring with Apple to adopt the controversial agency model, in an attempt to increase ebook prices and quash Amazon as a competitor.

Last August, Hachette, HarperCollins, and S&S settled with the U.S. government, reimbursing ebook consumers for more than $69 million. Penguin settled in December and Macmillan in February, leaving Apple as the sole defendant. The original lawsuit filing alleges that the publishers colluded in “private dining rooms of upscale Manhattan restaurants,” an accusation denied by all parties in affidavits submitted to the court.