Example auction: 1D – 1S – 1NT. Should responder bid 2S on a 5 card suit and a minimal hand? I used to be of the opinion that responder should not, normally. Then I read the Robinson’s Roundtable article on this subject and I’ve changed my opinion. There are other variables in play, such as whether opener can rebid 1NT with a singleton spade and how likely opener is to raise you with 3 spades on a hand otherwise flawed for no-trump. (example: opener has a small doubleton heart and 3 spades; they might raise to 2S with the ruffing value.) If your partner will raise you with 3 spades frequently or if your partner can have a singleton spade and still rebid 1NT then I think you should avoid the 2S bid. Otherwise, I think you usually should.
Of course, with game-invitational values or better responder can make a new minor forcing bid to ask about 3 card support, so the rebid of 3S, say, should promise 6 spades.