There are two issues here:

1) A ShardingTest can be started with autosplit enabled or disabled through the "enableAutoSplit" option. Autosplit can be disabled later through st.disableAutoSplit(), but there is no helper to re-enable it.

2) If not specified, enableAutoSplit defaults to the enableBalancer setting (which defaults to false). However, autosplit is not toggled on start/stopBalancer. Should it be?

Note: On 3.2, re-enabling autosplit at runtime would require restarting mongoses.