Those interested in testing optimizers may have a look at equivalence modulo testing, a fascinating research field:

https://dl.acm.org/doi/10.1145/2666356.2594334

It would have been nice if the article explained what an optimizer is in this case?

I will add "compiler" before "optimizer" and link to the toy optimizer series

Thanks! I had to go to the rest of your site to make sense of it so that seems like the right approach.

Fuzzing your own optimizer before shipping it is the kind of thing that sounds obvious in hindsight and almost nobody does upfront.