DRIVERS-1677 : I suggest that drivers do their implementation of this ticket in tandem with their implementation of DRIVERS-1673 which adds command log messages. This way the driver will have actual log messages to emit and test and can confirm that their logging implementation and test code works as expected. The logging spec can be found here . The unified test format changes can be found here . To summarize: Client entities may now have a new observeLogMessages property specifying logging configuration for the client Tests may now have a new expectLogMessages property specifying expected log messages to be produced during the test Two new special matching operators $$matchAsRoot and $$matchAsDocument have been added to enable logging assertions.