p2.put("trees", "fir, oak, maple");
        p1.update(p2);

        assertEquals(2, (Object) p1.size());
        Object o23 = p1.getComments("trees");
        assertEquals(List.of("#", "# List of trees", "#"), o23);
        Object o22 = p1.getProperty("trees");
        assertEquals("fir, oak, maple", o22);
        Object o21 = p1.getComments("fruits");