@Override
  void execute() {
    Set<String> hdfsRoots = getObjectStore().listFSRoots();
    if (hdfsRoots != null) {
      System.out.println("Listing FS Roots..");
      for (String s : hdfsRoots) {
        System.out.println(s);
      }
    } else {
      System.err.println("Encountered error during listFSRoot");
    }
  }
@Test
  public void testListFSRoot() throws Exception {
    String fsRoot1 = "hdfs://abc.de";
    String fsRoot2 = "hdfs://fgh.ji";

    ObjectStore mockObjectStore = Mockito.mock(ObjectStore.class);
    when(mockObjectStore.listFSRoots()).thenReturn(Sets.newHashSet(fsRoot1, fsRoot2));

    OutputStream os = new ByteArrayOutputStream();
    System.setOut(new PrintStream(os));

    MetaToolTaskListFSRoot t = new MetaToolTaskListFSRoot();
    t.setCommandLine(new HiveMetaToolCommandLine(new String[] {"-listFSRoot"}));
    t.setObjectStore(mockObjectStore);
    t.execute();

    assertTrue(os.toString() + " doesn't contain " + fsRoot1, os.toString().contains(fsRoot1));
    assertTrue(os.toString() + " doesn't contain " + fsRoot2, os.toString().contains(fsRoot2));
  }