@Override
  public void postGetOp(final ObserverContext<? extends RegionCoprocessorEnvironment> c,
    final Get get, final List<Cell> results) {
    RegionCoprocessorEnvironment e = c.getEnvironment();
    assertNotNull(e);
    assertNotNull(e.getRegion());
    assertNotNull(get);
    assertNotNull(results);
    if (
      e.getRegion().getTableDescriptor().getTableName()
        .equals(TestRegionObserverInterface.TEST_TABLE)
    ) {
      boolean foundA = false;
      boolean foundB = false;
      boolean foundC = false;
      for (Cell kv : results) {
        if (CellUtil.matchingFamily(kv, TestRegionObserverInterface.A)) {
          foundA = true;
        }
        if (CellUtil.matchingFamily(kv, TestRegionObserverInterface.B)) {
          foundB = true;
        }
        if (CellUtil.matchingFamily(kv, TestRegionObserverInterface.C)) {
          foundC = true;
        }
      }
      assertTrue(foundA);
      assertTrue(foundB);
      assertTrue(foundC);
    }
    ctPostGet.incrementAndGet();
  }
A sample region observer that tests the RegionObserver interface. It works with
TestRegionObserverInterface to provide the test case.
hbase-server/src/test/java/org/apache/hadoop/hbase/coprocessor/SimpleRegionObserver.java