It happens quite frequently that short answers (Title + Code) appear in the Low Quality review queue, due to the automatic flagging mechanisms.
In most cases, the answer "Looks OK". However, there are cases where the answer was posted in good faith, but the output in some scenarios are incorrect, a new user has hardcoded the input or something similar.
In general, the consensus seems to be:
If the answer is invalid without the poster's knowledge, it shouldn't be deleted without notifying the poster first and giving him some time to fix his mistake.
[...] I think deleting an accidentally invalid answer on sight is an unnecessarily unpleasant experience for the poster, [...]
Give the poster time to fix or self-delete his invalid answer.
If a sufficient amount of time has passed (say 48 hours) or the answer was deliberately invalid, flag the answer as in need of moderator intervention, providing an explanation of why it is invalid.
When these answers appear in the review queues, it feels wrong to choose: "Looks OK", since it's actually an invalid answer. This might lead to the answer going undeleted indefinitely, unless someone flags it (or votes to delete) after 48 hours have passed. Users can't be expected to go back and check on an answer two days later to see if it's been updated.
Voting to delete feels equally wrong, since it's unnecessarily harsh (according to the consensus). Skipping it doesn't make sense, since someone else will have to review it instead.
Assuming OP has received a comment, but "sufficient amount of time" has not passed, should we say that the answer Looks OK?