Juju has the ability to use lxc or kvm to deploy services, this is done by the local provider, but sometimes during development you may want to have one environment up-n-running all the time for testing and you may need another one to run amulet tests, well at the beginning this wasn't obvious to me that this could be achieved, but then I found how to do it :)
Here is how you can have two different environments:
environments:
local:
type: local
default-series: trusty
lxc-clone: true
container: kvm
network-bridge: br0
lxc:
type: local
default-series: trusty
lxc-clone: true
network-bridge: lxcbr0
state-port: 37018
api-port: 17071
That is the relevant portion of my ~/.juju/environments.yaml, I use one environment with kvm and the other one with lxc.
If you're curious, the trick is to change the state-port and api-port.
I hope this helps you.