resmoke.py only verifies that the master and slave in the deployment are reachable, but does not wait for the slave to finish its initial sync. It is possible for a test to finish before the initial sync such that when the slave goes to apply the oplog entries, it causes an error. For example, renaming a collection could fail due to the target namespace already existing on the slave from the initial clone.

class MasterSlaveFixture(interface.ReplFixture):
    ...

    def await_ready(self):
        self.master.await_ready()
        self.slave.await_ready()

The solution is to do a replicated write of w=2 during the await_ready() function before running any tests.