public OrderedProperties addPair(String key, String value) {
        pairs.put(key, value);
        return this;
    }
@Test
    public void propertiesContainsEscapes() throws IOException {
        OrderedProperties pairs = new OrderedProperties()
            .addPair(" leading", " leading")
            .addPair("trailing ", "trailing ")
            .addPair("with\\escape", "with\\escape\r\n\f\t")
            .addPair("two\nparts", " leading and trailing ")
            .addPair("\\", "\\")
            .addPair("", "");
        propertiesCompatibility(pairs);
    }