It's not unusual to ask a developer to prove their skills on a simple real-world case, in the later stages of interviewing. We don't always get useful results from this - in fact we usually re-use the same bug on many people, to make it easier for us to evaluate the attempts we get back. You must have been lucky. You can't expect a bug fix to be the ONLY criteria for hiring, though. Again it's quite normal to get many applicants for every job, tests like this are required to evaluate and rank applicants. Best of luck in your work.