1: Focus on possible business logic exception: the business logic exception can be compared can be found quickly through a variety of input and output expected.
2: Focus on Possible operating logic exception: as copy objects; object reference, etc. When such abnormal code logic look hard to find; the code is written in the brain to try to run it to see if there will be such an exception, this also with relevant experience and vigilance.
3: commonsense concerned about the possible exception: as time zone differences will be; Again Es update will delay; these also require vigilance.