Bring him to the box, and verbally encourage him. 70% of the time, he'll poop.

I heard of somebody who trolled their cat owning housemate by immediately cleaning the litter box after the cat pooped for a week, to make them think the cat wasn't pooping, then they took a huge dump in the litter box.

That somebody was George Clooney: https://www.youtube.com/watch?v=Qa_HnP9TP5s

Wow that’s impressive

Depends on the cat -- mine likes to follow me down to the basement and go when I'm in the middle of cleaning the litterbox.

I wonder whether that’s a neurotic thing about wanting clean litter or an emotional support thing. Your cat might only feel safe enough to go potty with you nearby. Just guessing with little info admittedly.

I don't know! There are counterexamples to both hypotheses: She'll often go before I actually start cleaning, so if it's clean litter, she's not very good at recognizing it; and similarly, while she likes to poop in my face, it's not the only time she uses the box, so I can't say she feels uncomfortable without me, either. I'd be more inclined to say the latter (or some variant), since she also likes to come visit me + keep watch while I use the bathroom, if I don't latch the door shut.