Just needed a fast way to set up facts with a couple of commands on
the machine where I'm using/testing puppet manifests.
Surprissingly I found what I was looking for digging in Vagrant
code. Put your facts in environment variables, prefixed with
'FACTER_':
# Define your facts as variables
export FACTER_YOURCUSTOMFACT=value1
export FACTER_OTHERFACT=value2
puppet apply /path/to/puppet/test/main.pp
Happy testing!