@Test
void applyLeavesAlreadyEmptyListUntouched() {

    final HeaderFilter unit = removeHeaders((name, value) ->
            "Set-Cookie".equals(name));
    final HttpHeaders headers = HttpHeaders.of("Set-Cookie");
    final HttpHeaders actual = unit.filter(headers);
    assertSame(actual, headers);
    assertFalse(actual.isEmpty());
}