It was a few years ago, but probably one of the worst experiences I've ever had. The interview went very well, they sent an assignment, I carefully read a really bad explanation of the task. I worked hard to make it and created way more than required. They never replied, and when I asked for the result after two weeks (at least to know the summary even if it's negative), they replied in 4 weeks with the answer. It was just not respectable towards my effort however good or bad it was (but it was definitely acceptable).