A recruiter contacted me and set up a technical phone interview. The interview question was of average difficulty. I didn't cover a corner case, and when I asked the interviewer to add code to cover a specific corner case, he stated I was out of time. I didn't get to move on to a second interview. I feel my answer was good enough for screening purposes (one would assume the first phone interview is the screening interview). However, as humans, talking over the phone while coding, we might not be in the best state to cover all cases, especially if it's just a screening call.