@Test
    void testSubProperties() {
        PropertyMap map = new PropertyMap() {
            {
                set("a.e", "1");
                set("a.f", 2);
                set("b.e", "3");
                set("f", 3);
                set("e", "2");
                set("d", "a");
            }
        };

        SubProperties sub = new SubProperties("a", map);
        assertEquals("1", sub.get("e"));
        assertEquals(2, sub.get("f"));
        assertNull(sub.get("d"));
        assertEquals(new HashSet<>(List.of("e", "f")), sub.listProperties("").keySet());
    }
@author <a href="mailto:arnebef@yahoo-inc.com">Arne Bergene Fossaa</a>
container-search/src/test/java/com/yahoo/search/query/properties/SubPropertiesTestCase.java