If it's medical research, I don't have much of an issue with it. As long as the animals are kept in suitable conditions, with enough space, company of the same species and things to provide stimulation, I think it's ok. I'm an animal lover, and I wish animal testing wasn't necessary, but at this point in time it is. The only thing I have a big issue with is vivisection. I can't think of anything that a vivisection could show us that a necropsy couldn't. Cosmetics testing, I definitely take issue with. There are certainly non-animal alternatives to testing cosmetics, especially with today's technology and science.
Even though I'm not exactly fond of the idea of animal testing, I wouldn't describe it as torture. I'm talking purely about medical research, which is the only type I've had firsthand experience with. All the procedures I've seen, the animals were dosed with whatever drug, then put back into their pen/cage and observed. As the animals get used to being dosed, they stop being distressed. It's part of their routine. They're not scared or in pain. Just a few seconds of discomfort and it's done. They're not getting hacked at or 'experimented on', really. For the most part they're left alone.
When they can, most animal testing places use the 3 Rs anway. Reduction, refinement, replacement. Nobody wants to test on animals. But since it has to be done(for now) people are constantly seeking to use fewer animals in studies, to improve techniques so the animals suffer as little as possible, and to use alternatives to animals wherever possible.