I think the "coverageLog" function is a good way to filter out mocha log and coverage log, but there are some debug log still need to clear away. And the debug log is aslo sent by console log in MochaReporter. So If I use "coverageLog" function to filter it still need to modify the RunnerStreamProxy to remove log.
Maybe there exist another pretty way to solve but I think we cannot avoid invasive code here.