@Test
void testRequireKeys_4args() {

    assertThrows(NoSuchElementException.class, () -> {
        final Map<String, String> map = new HashMap<>();
        map.put("A", "Tryggve");
        map.put("B", "Sven");
        map.put("C", "Glenn");
        final Map<String, String> result = NullUtil.requireKeys(map, "A", "B", "Z");
    });
}