@Override
  public boolean isSet(PropertyKey key) {
    return mProperties.isSet(key) && isResolvable(key);
  }
@Test
  public void isSet() {
    assertFalse(mConfiguration.isSet(PropertyKey.ZOOKEEPER_ADDRESS));
    mConfiguration.set(PropertyKey.ZOOKEEPER_ADDRESS, "address");
    assertTrue(mConfiguration.isSet(PropertyKey.ZOOKEEPER_ADDRESS));
  }