Wow.. downvotes?

I guess I need to add an explanation or something?

Docker allows very quick startup of containers (and for testing purposes the distinctions between containers and VM aren't important. Additionally, the easy command line and app ecosystem Docker gives you over just using Linux containers is a big advantage here.).

I prefer the Mock method for two reasons:

1) It's extremely fast - much faster than even docker would be.

2) The data you use for mocks can form part of your documentation (if done properly).

+1 docker and jenkins and is a happy medium between speed and isolation.