@Test
  public void testOnConfigurationChange() {
    // fallbackEnabled default is false
    assertFalse(loadBalancer.isFallbackEnabled());

    // change FALLBACK_GROUP_ENABLE_KEY from false to true
    conf.setBoolean(RSGroupBasedLoadBalancer.FALLBACK_GROUP_ENABLE_KEY, true);
    loadBalancer.onConfigurationChange(conf);
    assertTrue(loadBalancer.isFallbackEnabled());

    // restore
    conf.setBoolean(RSGroupBasedLoadBalancer.FALLBACK_GROUP_ENABLE_KEY, false);
    loadBalancer.onConfigurationChange(conf);
    assertFalse(loadBalancer.isFallbackEnabled());
  }
Test BOGUS_SERVER_NAME among groups do not overwrite each other.
hbase-server/src/test/java/org/apache/hadoop/hbase/master/balancer/TestRSGroupBasedLoadBalancer.java