Out of the linked issues these all seem like they would be "easy" to hit given enough data:
https://issues.apache.org/jira/browse/SPARK-13279
https://issues.apache.org/jira/browse/SPARK-13850
https://issues.apache.org/jira/browse/SPARK-13958
https://issues.apache.org/jira/browse/SPARK-14363
Out of the linked issues these all seem like they would be "easy" to hit given enough data:
https://issues.apache.org/jira/browse/SPARK-13279
https://issues.apache.org/jira/browse/SPARK-13850
https://issues.apache.org/jira/browse/SPARK-13958
https://issues.apache.org/jira/browse/SPARK-14363