Good vs Bad Tests

bad_foo_spec.rb

# This basically tests that Puppet works. It just re-creates your Puppet code in a different DSL.
# ANY change to the existing params on this resource will require that you update your tests.
describe 'foo' do
  let(:params) { :param => 'somevalue' }
  
  it do
    should contain_file('bar').with({
      :ensure  => present, 
      :owner   => root,
      :group   => root,
      :mode    => 0644,
      :content => 'somevalue'
    })
  end
end

good_foo_spec.rb

# Better. This tests the interface instead of the implementation. You can change the implementation
# without updating the tests, as long as the interface stays the same. This is how you refactor!
describe 'foo' do
  let(:params) { :param => 'somevalue' }
  
  it 'should contain the expected resources' do
    should contain_file('bar').with_content(/^somevalue$/)
  end
end

init.pp

class foo (
  $param = value,
) {

  file { 'bar':
    ensure  => present,
    owner   => root,
    group   => root,
    mode    => 0644,
    content => $param,
  }
}