// start a third datanode
cluster.startDataNodes(conf, 1, true, null, null);
ArrayList<DataNode> datanodes = cluster.getDataNodes();
assertEquals(datanodes.size(), 3);
DataNode dataNode = datanodes.get(2);
// report corrupted block by the third datanode
cluster.getNameNode().namesystem.markBlockAsCorrupt(blk,
new DatanodeInfo(dataNode.dnRegistration ));