@Test
  public void testOpenRegionReplica() throws Exception {
    openRegion(HTU, getRS(), hriSecondary);
    try {
      // load some data to primary
      HTU.loadNumericRows(table, f, 0, 1000);

      // assert that we can read back from primary
      Assert.assertEquals(1000, HBaseTestingUtil.countRows(table));
    } finally {
      HTU.deleteNumericRows(table, f, 0, 1000);
      closeRegion(HTU, getRS(), hriSecondary);
    }
  }
Tests for region replicas. Sad that we cannot isolate these without bringing up a whole cluster.
See {@link TestRegionServerNoMaster}.
hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestRegionReplicas.java