@Test
void testRequireKeys_4args_2() {

    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", "C");
    assertEquals(map, result);
}