Running Rspec fails if variables can be passed to a class in Puppet

Problem

If variables can be passed to a Puppet class, e.g.:

class module_name (
  $variable='hello_world'
) {
  package { 'package_name': }
}

and rspec is run it fails, i.e.:

[user@host module_name]$ rspec
...............................FFFFFFFFFFFF..........................................

Failures:

  1) opsview should contain Class[module_name]
     Failure/Error: it { should contain_class('module_name') }
     Puppet::Error:
       Error from DataBinding 'hiera' while looking up 'module_name::variable': 
       FileSystem implementation expected Pathname, got: 'Hash' on node host
     # /usr/share/ruby/vendor_ruby/puppet/resource.rb:393:
         in `rescue in lookup_with_databinding'
     # /usr/share/ruby/vendor_ruby/puppet/resource.rb:387:
         in `lookup_with_databinding'
     # /usr/share/ruby/vendor_ruby/puppet/resource.rb:381:
         in `lookup_external_default_for'

Main issue

Error from DataBinding while looking up FileSystem implementation expected Pathname, 
got: 'Hash' on node

Configuration

Versions

[vagrant@vm-one opsview]$ puppet --version
3.7.5
[vagrant@vm-one opsview]$ rspec --version
3.2.2

Spec_helper

[vagrant@vm-one opsview]$ cat spec/spec_helper.rb
require 'rspec-puppet'
require 'hiera-puppet-helper'

fixture_path = File.expand_path(File.join(__FILE__, '..', 'fixtures'))

RSpec.configure do |c|
  c.module_path = File.join(fixture_path, 'modules')
  c.manifest_dir = File.join(fixture_path, 'manifests')
  c.hiera_config = '/etc/puppet/hiera.yaml'
end

at_exit { RSpec::Puppet::Coverage.report! }

Attempt

1. According to this Q&A hiera-puppet-helper is causing the issue. Rspec-puppet seems to support testing of hiera and 'hiera-puppet-helper' could be replaced. Ok perhaps this solves the issue, but what is causing the issue?


2. This post contains the same issue, but not a solution to solve the issue


3. This post indicates that removing the class parameters solves the issue, but this class is used by multiple modules and therefore this is not a solution.