EVFILT_EMPTY
{ "EVFILT_EMPTY", EVFILT_EMPTY, 0, &file_filtops, 0 },
case EVFILT_EMPTY:
ATF_REQUIRE(event.filter == EVFILT_EMPTY);
EV_SET(&event, writefd, EVFILT_EMPTY, EV_ADD, 0, 0, NULL);
ATF_REQUIRE(event.filter == EVFILT_EMPTY);