@Test
@SuppressWarnings("null")
public void testOf() {

    assertThatThrownBy(() -> WorkspaceFamily.of(null)).isInstanceOf(NullPointerException.class);
    assertThat(WorkspaceFamily.of(empty)).isSameAs(empty);
    assertThat(WorkspaceFamily.of(new LinearId())).isEqualTo(empty);
    assertThat(WorkspaceFamily.of(new LinearId("hello", "world"))).isEqualTo(dual);
    assertThat(LinearId.of(dual)).isEqualTo(new LinearId("hello", "world"));
}