How are you using Mongo? What version of the server and driver are you using?

I'm developing the driver and our mock server could now be replaced by using the failPoint features of mongodb. We should remove the mock server in favor of always testing against real servers.

What is the feature/improvement you would like?

There is likely good follow up work to be done here to improve the experience of deploying specialized environments. (ex. sharded cluster with a specific number of nodes)

What use case would this feature/improvement enable?

Our mock server implementation doesn't speak in OP_MSG so it is becoming obsolete.