// Headers should be stored in lowercase
        assertTrue(result.containsKey("content-type"));
        assertTrue(result.containsKey("content-length"));
    }

    @Test
    public void testHeadersWithNullKey() {
        CurlResponse response = new CurlResponse();
        Map<String, List<String>> headers = new HashMap<>();
        headers.put(null, Arrays.asList("value"));