@Test
public void mutable() {

    ObjectValue ov = PropertyValue.createObject("foo");
    ov.addList("list");
    assertThat(ov.isImmutable()).isFalse();
    ObjectValue ov2 = ov.mutable();
    assertThat(ov2.isImmutable()).isFalse();
    assertThat(ov == ov2).isTrue();
}