This would be added to the ReshardingTest fixture. ReshardingTest#_checkConsistency() compares the contents of the existing sharded collection with the temporary resharding collection. It is conceivable (albeit unlikely) that the sharded collection ends up with different contents than what was in the temporary resharding collection. For completeness, we should also confirm that the contents of the existing sharded collection after the reshardCollection command has returned match the contents of the temporary resharding collection previously read. Max's thought would be to either run the dbHash command for the particular namespace before and after or $out the contents of the temporary resharding collection and use DataConsistencyChecker.getDiff().