This is really a symptom of the kind of nonsensical divisions of modules that are in HDFS and MapReduce. Ideally, all of this native code would be hdfs-client. Then when a change is made to to that code, this code will also get tested.
This does, however, underscore that committers really really really need to pay attention to the qbt report after they do a commit. If tests that weren't failing before are now consistently failing, it's likely because there was a side effect of a recent change.