If you see something like the following
... java.lang.NullPointerException: null at org.apache.hadoop.hdfs.MiniDFSCluster.startDataNodes at org.apache.hadoop.hdfs.MiniDFSCluster.<init> at org.apache.hadoop.hbase.MiniHBaseCluster.<init> at org.apache.hadoop.hbase.HBaseTestingUtility.startMiniDFSCluster at org.apache.hadoop.hbase.HBaseTestingUtility.startMiniCluster ...
or
... java.io.IOException: Shutting down at org.apache.hadoop.hbase.MiniHBaseCluster.init at org.apache.hadoop.hbase.MiniHBaseCluster.<init> at org.apache.hadoop.hbase.MiniHBaseCluster.<init> at org.apache.hadoop.hbase.HBaseTestingUtility.startMiniHBaseCluster at org.apache.hadoop.hbase.HBaseTestingUtility.startMiniCluster ...
... then try issuing the command umask 022 before launching tests. This is a workaround for HDFS-2556