When we study how to image the radioactive atoms in hospital scanners, we use 3D-printed organs so we don’t have to test on people or animals. There are also 3D-printed mice that can be used. The new drugs do need to be tested on mice before they can be used in people but I don’t work in that area myself.
I don’t have to try very hard: no testing of that sort in my work. But I am not 100% opposed, provided it is done only when essential, and humanely: in research funding these days, anything with ethical issues requires extra forms, procedures, and proof that it is completely unavoidable and that the benefits far outweigh the downsides. I’m sure there’s room yet for improvement — there always is — but it’s good to know that this is taken very, very seriously, by e.g. the European Research Council.
My research doesn’t use animals and I don’t specifically buy products that are cruelty free but I recognise that some animal research is inevitable as you can’t assume something that works in a petri dish in a lab actually transfers to humans. Animal testing is very strictly regulated for research purposes though
Not testing on animals is pretty effortless in my case. Particle physics research at the smallest scales doesn’t eventually need to be tested on humans, so there’d be no reason to test on animals either.