Animal testing not only benefits humans but it benefits other animals as well. There are many medications that animals are given and these medications were tested on other animals. Everything that is tested on animals is not necessarily for human use only.
A con about animal testing is in regard to what is being tested. If we are testing makeup on a animal and end up blinding the animal then I think it is not justified.
Animal testing should be limited to what it is that it attempting to be discovered. If it is going to save lives then I think there is justification in it, but it definitely needs to be regulated.
The pros of animal testing is that we can obtain information on how organisms with similar working systems as humans can process and react to new medications and treatments prior to applying them to human beings. We can use animals to try ways to cure illnesses, to employ treatment options, and to choose medicines that can actually help.
The cons of animal testing rely on the ethical and moral arguments that arise as a result of using a live body for potentially dangerous researches that might end up in their death. Doing this might make humans seem as blood-thirsty people who can use and dispose of living organisms with out respect. Although that is not necessarily the case, many think that it is so, and that is when animal testing becomes a current issue.
Animal testing is a great benefit to people, in my opinion. The major pro of this testing is that it allows people to test drugs and other such things to be sure (or as sure as possible) that the drugs will not harm people. If there were no animal testing, we would have to take new drugs or new chemicals and test them on people. We would essentially have to just guess that something wouldn't hurt people.
The only real con is if you are an animal. It is surely horrible to do these things to animals -- give them cancer, things like that. But this does not, in my opinion, harm human beings in any direct way.