@Test
public void shouldReturnNullIfCookiesIsEmpty() {

    GetCookieFromRequestRule rule = new GetCookieFromRequestRule();
    FullHttpRequest request = mock(FullHttpRequest.class);
    HttpHeaders headers = mock(HttpHeaders.class);
    when(request.headers()).thenReturn(headers);
    when(headers.get(eq("Cookie"))).thenReturn(null);
    assertNull(rule.resolve(request, "key3"));
}