@Test
  public void testDowngradeOrchestration() throws Exception {
    Map<String, UpgradePack> upgrades = ambariMetaInfo.getUpgradePacks("HDP", "2.1.1");
    assertTrue(upgrades.containsKey("upgrade_test"));
    UpgradePack upgrade = upgrades.get("upgrade_test");
    assertNotNull(upgrade);

    Cluster cluster = makeCluster();

    UpgradeContext context = getMockUpgradeContext(cluster, Direction.DOWNGRADE,
        UpgradeType.ROLLING, repositoryVersion2200);

    List<UpgradeGroupHolder> groups = m_upgradeHelper.createSequence(upgrade, context);

    assertEquals(7, groups.size());

    assertEquals("PRE_CLUSTER", groups.get(0).name);
    assertEquals("OOZIE", groups.get(1).name);
    assertEquals("HIVE", groups.get(2).name);
    assertEquals("CORE_SLAVES", groups.get(3).name);
    assertEquals("CORE_MASTER", groups.get(4).name);
    assertEquals("ZOOKEEPER", groups.get(5).name);


    UpgradeGroupHolder postGroup = groups.get(6);
    assertEquals("POST_CLUSTER", postGroup.name);
    assertEquals("Finalize Downgrade", postGroup.title);
    assertEquals(3, postGroup.items.size());
    assertEquals("Confirm Finalize", postGroup.items.get(0).getText());
    assertEquals("Execute HDFS Finalize", postGroup.items.get(1).getText());
    assertEquals("Save Cluster State", postGroup.items.get(2).getText());
    assertEquals(StageWrapper.Type.SERVER_SIDE_ACTION, postGroup.items.get(2).getType());

    assertEquals(4, groups.get(0).items.size());
    assertEquals(8, groups.get(1).items.size());
    assertEquals(6, groups.get(2).items.size());
    assertEquals(6, groups.get(3).items.size());
    assertEquals(8, groups.get(4).items.size());
  }
Verify that a Rolling Upgrades restarts the NameNodes in the following order: standby, active.
@throws Exception
ambari-server/src/test/java/org/apache/ambari/server/stack/upgrade/orchestrate/UpgradeHelperTest.java