mock facter version based on puppet version

spec/spec_helper.rb

@@ -42,6 +42,18 @@
 end
 
 RSpec.configure do |c|
+  # getting the correct facter version is tricky. We use facterdb as a source to mock facts
+  # see https://github.com/camptocamp/facterdb
+  # people might provide a specific facter version. In that case we use it.
+  # Otherwise we need to match the correct facter version to the used puppet version.
+  # as of 2019-10-31, puppet 5 ships facter 3.11 and puppet 6 ships facter 3.14
+  # https://puppet.com/docs/puppet/5.5/about_agent.html
+  c.default_facter_version = if ENV['FACTERDB_FACTS_VERSION']
+                               ENV['FACTERDB_FACTS_VERSION']
+                             else
+                               Gem::Dependency.new('', ENV['PUPPET_VERSION']).match?('', '5') ? '3.11.0' : '3.14.0'
+                             end
+
   # Coverage generation
   c.after(:suite) do
     RSpec::Puppet::Coverage.report!