I'd add a tad of context to my original comment. I probably have a lot of hard feelings against companies hiring behavior, some justified, some merely emotional. Karat however went over the top. They're trying to be extra-nice by triple checking that everything went well, but don't follow up on negative comments. It's not rocket science to properly define test cases and supported logic to run them so that the candidate focus on the implementation, the screening implements it, but not the timed phone call. Also, tricking candidates with edges cases not mentioned orally but not written is borderline dishonest.