assertTrue("Should contain other key", Arrays.asList(keys).contains("other"));
        assertEquals("Should have 2 keys", 2, keys.length);
    }

    public void test_isEmpty_and_size() {
        Map<String, Object> parentMap = new HashMap<>();
        DocMap docMap = new DocMap(parentMap);

        assertTrue(docMap.isEmpty());
        assertEquals(0, docMap.size());