I had a first interview with HR, then they sent me a written task to complete and then completely disappeared without any feedback. The test was fairly time-consuming and it would have been nice to at least receive a feedback.

There was a first interview with HR, then a second with the team I would work with, a written assignment and a final call with HR. After the assignment, they never replied to me, and never sent me feedback despite my follow-ups. I feel this was very unprofessional to just disappear in the middle of a recruiting process, after time and effort spent in completing the assignment.