DocMap docMap = new DocMap(parentMap);

        docMap.put("nullKey", null);
        assertTrue(docMap.containsKey("nullKey"));
        assertTrue(docMap.containsValue(null));
        assertNull(docMap.get("nullKey"));

        assertNull(docMap.put("nullKey", "newValue"));
        assertEquals("newValue", docMap.get("nullKey"));
    }

    @Test
    public void test_map_interface_compliance() {

    }

    // Test getAsString with null value
    @Test
    public void test_getAsStringWithNullValue() {
        dataStoreParams.put("nullKey", null);
        assertNull(dataStoreParams.getAsString("nullKey"));
    }

    // Test getAsString for non-existent key
    @Test
    public void test_getAsStringNonExistentKey() {
        assertNull(dataStoreParams.getAsString("nonexistent"));