@Test
public void testHashCode() {

    assertThat(EMPTY.hashCode())
            .isEqualTo(EMPTY.hashCode())
            .isNotEqualTo(SECTOR_REGION.hashCode());
    assertThat(SECTOR_REGION.hashCode())
            .isEqualTo(SECTOR_REGION.hashCode())
            .isNotEqualTo(INDUSTRY.hashCode());
    assertThat(INDUSTRY.hashCode())
            .isEqualTo(INDUSTRY.hashCode())
            .isEqualTo(SECTOR_REGION.child("industry").hashCode());
}