@Test
public void testChild() {

    assertThatThrownBy(() -> EMPTY.child("hello")).isInstanceOf(IllegalArgumentException.class);
    assertThatThrownBy(() -> EMPTY.child((String) null)).isInstanceOf(IllegalArgumentException.class);
    assertThatThrownBy(() -> EMPTY.child("hello", null)).isInstanceOf(IllegalArgumentException.class);
    assertThatThrownBy(() -> EMPTY.child((String[]) null)).isInstanceOf(NullPointerException.class);
}