The scientific testing on animals have a good part but have a bad part too.
The good part are that we can create new animals or change is structure eg. But like everything there is also a bad part is that the animals could be die or whatever else.
Now, the good things about scientific testing on animals is that we know all the features of the animal (hormones, enzymes ...) and we can also create a new animal or gene. Also if the animal has any disease we can experiment with the animal to find a vaccine or whatever else to save the animals who have the same disease.
On the other hand there are bad things like the animal could be die or be more aggressive eg. More scientifics said that the testing are safe but you didnt know this until you try, can go right or wrong if it goes wrong, the animal will suffer. The Animals also have feelings like humans so they also suffer pain.
In conclusion, my opinion are that we shouldn't experiment with animals because animals don't deserve to be made to suffer becasue well.. many tests nothing happens but others if happens.