Hoffman's Test was part of John's new plans. A wax-coated tape in Jigsaw (John's) stomach was found during his autopsy in Saw IV. At first, it was thought to be a message that taunted the authorities, but as the movie progressed, it was revealed that John had a second apprentice besides Amanda.
The second apprentice was revealed to be Mark Hoffman when the film neared its conclusion, and the tape found in John's stomach was meant for him. It stated that although he may be the "last man standing" he would not walk away untested, that "the games have just begun", hinting that the tape was a prelude to his testing.
Are you there, detective? If so, you are probably the last man standing. Now, perhaps you will succeed where the others have failed. You feel you now have control, don't you? You think you will walk away untested. I promise that my work will continue. That I have ensured, by hearing this tape, some will assume that this is over, but I am still among you. You think it's over just because I am dead. It's not over. The games have just begun.
John warns Hoffman