While reviewing, I was asked to give my opinion about Why is geo-redundant DNS necessary for small sites?. This seemed odd to me, so I assumed it was a test to see if I was paying attention. I clicked that the question seemed fine to me and I passed the test.
Normally, when seeing a question worded like that one, I'd check the matching canonical question, see if it answers the problem and point there if it does. But in this case, I clicked Looks OK because there was a nice yellow block above the question stating that it was a canonical question.
Is it intended that canonical questions can appear in the review queue as a test? For me the correct response was not obvious, my hunch was that I had to accept it because canonical questions exist and it probably had a lot of upvotes, but I did not judge the question by its content.
paying attention. Even though this is probably a weird side-effect of the way ServerFault has implemented canonical questions, I'd say it's one of my favorite review audits. Less random chance of incorrect action and easy to judge for a person paying attention.