This all depends on how you are using Fabrication.
Nesting parameters for testing controllers is a world of hurt and you will need some hand crafting for your params hash.
For models you should try this:
Fabricator(:service) do
name "Service Name"
description "Lorem ipsum est lauda en radios"
locations {[Fabricate.build(:location)]}
end
Fabricator(:location) do
name "Special Club"
service
end
You probably don't need the :inverse_of
for your relations.