assertNotNull(json);
        // JSON should properly escape quotes
        assertTrue("JSON should be valid", json.startsWith("{") && json.endsWith("}"));
    }

    @Test
    public void test_toJsonString_withAllFields() {
        String[] text = { "test" };
        String[][] readings = { { "reading" } };
        String[] fields = { "field1" };
        String[] tags = { "tag1" };
        String[] roles = { "role1" };