@Test public void doesNothingWhenResponseSetsSessionCookie() throws Exception {

  ImmutableMap<String, NewCookie> immutableResponseCookies =
      ImmutableMap.of(SESSION_COOKIE, NewCookie.valueOf(cookie.getValue()));
  when(response.getCookies()).thenReturn(immutableResponseCookies);
  filter.filter(request, response);
  assertThat(response.getCookies()).isSameAs(immutableResponseCookies);
  assertThat(response.getHeaders()).doesNotContainKey(SET_COOKIE);
}