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BugZero found this defect 2603 days ago.
As seen in BF-6014, it's possible for the shell to take more than one second to start up and check the output of currentOp, so by the time it does so, the operation it's waiting for (the getMore with a maxTimeMS of 1 second), can complete.
xgen-internal-githook commented on Fri, 4 Aug 2017 15:32:57 +0000: Author: {'username': 'cswanson310', 'email': 'charlie.swanson@mongodb.com', 'name': 'Charlie Swanson'} Message: SERVER-30289 Ensure shell starts before getMore in change stream test. Branch: master https://github.com/mongodb/mongo/commit/bb8a59837b1be306cb42e0a3e84ffe42290f79ea