haskell megaparsec operators -> should return [0] somewhere high in the result set. Found it on the third page of Brave Search. For comparison, it's the very first result on Google, second page for Bing, and the third page for DuckDuckGo.
Sure, it's a bit obscure, and I don't even write that much Haskell these days. But it's calibrated to determine whether I can rely on the search engine to quickly surface what I need to be productive, and whether I can trust its 'negative results' (I don't see what I want on the results page -> I need to refine my query or take a different approach). The version number returned in the URL also shows how well the engine handles keeping up with versioned documentation pages and aggregating 'link juice' between them.
I try this on every search engine alternative that pops up on HN. Very, very few pass. I find it often works like an adversarial example, yielding completely nonsensical results.
[0] https://hackage.haskell.org/package/megaparsec-5.2.0/docs/Te... (or any other megaparsec-#.#.# version)