public Configuration get() {
    // get() call returns the original conf, which is mutable by caller
    confMutated = true;
    return conf;
  }
@Test
  public void testConstruction() {
    assertNotNull(DEFAULT_SERIALIZABLE_CONF);
    assertNotNull(DEFAULT_SERIALIZABLE_CONF.get());
    thrown.expect(NullPointerException.class);
    new SerializableConfiguration(null);
  }