When I watched Saw movies, I thought that the traps for agent Strahm were set up by Kramer. I thought he was put into the water box by the masked guys from the end of Saw 3D and the moving-wall-room was made some time ago, because, you know, Kramer was a good planner.
But Wikipedia and other resources say that Strahm was tested by Hoffman. Despite Hoffman looking surprised when he saw Strahm alive after the water box, we can assume he just didn't believe in Peter being smart about the pen. But I cannot understand the second test (crush-room). He didn't intend to kill Strahm Amanda-like, why would he record 'I hope you learned to trust me' stuff otherwise. But what would he do if Strahm went into the coffin and survived? Because we saw that Hoffman murdered people easily in case of risk of disclosure. So was he going to let Strahm go? If he just wanted to crush him, why didn't he without risking in the hand-to-hand fight?
Also, the whole scene in that room seems strange. Did Hoffman really let Strahm force him into the glass box? Didn't look like that, and he looked a little shocked a few seconds after that despite the fact that he knew he was safe and Strahm had failed.
So, the question is: what were Hoffman's intentions when he went to the dumpster-room after Strahm? What was he going to do and what would he do if things went differently?