@Override
  public Object get(PropertyKey key) {
    return get(key, ConfigurationValueOptions.defaults());
  }
@Test
  public void systemVariableSubstitution() throws Exception {
    try (Closeable p =
        new SystemPropertyRule(PropertyKey.MASTER_HOSTNAME.toString(), "new_master").toResource()) {

      resetConf();
      assertEquals("new_master", mConfiguration.get(PropertyKey.MASTER_HOSTNAME));
    }
  }