If a test has very large fixtures, it's best to extract them to independent files using `my_fixture_read`: see https://github.com/puppetlabs/facter/blob/master/spec/unit/util/vlans_spec.rb#L38 and https://github.com/puppetlabs/facter/blob/master/spec/fixtures/unit/util/vlans/centos-5-no-vlans for an example of that.