In every editorial I see there “Problem Setter and Problem Tester”.
I know problem setter is one who makes the question.
My question is what does the problem tester do?
Tests the problem.
General rule: the more people try to solve the problem before it’s published in a contest, the lower chances of it containing a mistake are. So there’s someone assigned to solve the problem and give feedback on it to the setter.
Problem tester basically tests the logic of the problem with several test cases and comes out with corner cases which thereafter helps to examine the solutions we submit in any contests. 