I've seen many dog aggressive dogs pass the CGC class. They do take breed into consideration. Most times these classes show the dog does have a temper! 
A dog that shows no response and is laid back is going to fail the test (a much safer dog over all and I have seen these dogs fail because they do not react to anything). The test basically takes into consideration how the dog reacts and then recovers.
A dog that shows no response and is laid back is going to fail the test (a much safer dog over all and I have seen these dogs fail because they do not react to anything). The test basically takes into consideration how the dog reacts and then recovers.