@Test
public void getKeys() {

    ObjectValue ov = PropertyValue.createObject();
    PropertyValue val = new PropertyValue("k", "v");
    ov.setPropertyValue(val);
    PropertyValue val2 = new PropertyValue("k2", "v2");
    ov.setPropertyValue(val2);
    assertThat(ov.getKeys()).contains("k", "k2");
}