@Test
void testRequireKeys_2args_2_3() {

    final Map<String, String> map = new HashMap<>();
    map.put("A", "Tryggve");
    map.put("B", "Sven");
    final String[] arr = {"A", "B"};
    final Map<String, String> result = NullUtil.requireKeys(map, arr);
    assertEquals(map, result);
}