@Test
public void testHashcode() {

    assertThat(empty.hashCode())
            .isEqualTo(new LinearId("").hashCode())
            .isNotEqualTo(single.hashCode())
            .isNotEqualTo(dual.hashCode());
    assertThat(single.hashCode())
            .isEqualTo(new LinearId("single").hashCode())
            .isNotEqualTo(empty.hashCode())
            .isNotEqualTo(dual.hashCode());
    assertThat(dual.hashCode())
            .isEqualTo(new LinearId("hello", "world").hashCode())
            .isNotEqualTo(empty.hashCode())
            .isNotEqualTo(single.hashCode());
}