public OrderedProperties addMapPairs(Map<String, String> additionalPairs) {
        addIterablePairs(additionalPairs.entrySet());
        return this;
    }
@Test
    public void addMapPairs() {
        Map<String, String> additional = new LinkedHashMap<>();
        additional.put("fifth", "5");
        additional.put("first", "6");

        OrderedProperties pairs = createTestKeyValues().addMapPairs(additional);
        assertKeyOrder(pairs, "first", "second", "third", "FOURTH", "fifth");
        assertValueOrder(pairs, "6", "2", "3", "4", "5");
    }