assertTrue(json.contains("\"url\": \"https://example.com/page.html\""));
        assertTrue(json.startsWith("{"));
        assertTrue(json.trim().endsWith("}"));
    }

    @Test
    public void test_jsonFormatter_excludeFields() {
        final Map<String, Object> source = new LinkedHashMap<>();
        source.put("title", "Test");
        source.put("content", "Body");
        source.put("cache", "cached data");