IMHO, the easiest way to evaluate if a candidate can do a job is to give them tasks that they would do on the job. In your case, it looks like you should have t

IMHO, the easiest way to evaluate if a candidate can do a job is to give them tasks that they would do on the job. In your case, it looks like you should have them generate a report and try to find a bug in some business logic starting with an ambiguous problem statement.