The operation field isn't used for anything in our documentation. This was introduced in d5c501a2 and it looks like we missed cleaning it up in later commits that changed every other operation field to null.

The isMaster failpoint can't be reliably disabled again in these tests, causing subsequent test failures.

ChangeStream::getResumeToken() did not exist at the time this test was written; however, we do this assertion in testStartAfterOption().

Running mapReduce commands through the executeReadCommand helper will cause the driver to retry the operation, as it should not inspect the command to catch mapReduce commands. To avoid this, we run mapReduce commands through the generic command helper which generally doesn't retry reads.