assertNotNull(result);
        assertEquals(1, result.size()); // null key should be filtered out
        assertTrue(result.containsKey("content-type"));
    }

    @Test
    public void testHeadersWithNullMap() {
        CurlResponse response = new CurlResponse();

        response.setHeaders(null);

        assertNull(response.getHeaders());
    }

    @Test
    public void testGetHeaderValue() {