map_reduce_invalid_output_collection.js verifies a mapReduce merging to an already sharded collection will fail if that collection is not sharded by _id. For non-aggregation mapReduce, this relies on upserts without the full shard key being rejected (see SERVER-42916). SERVER-44382 allowed upserted documents in a sharded collection to have missing shard key fields, so the non-aggregation mapReduce cases in the test were disabled. They should be re-enabled after determining how mapReduce to a collection sharded by a key other than _id should behave.