I think I'd prefer:
```ruby
it 'should register the proxy' do
  should include_class('foreman_proxy::register')
  should contain_foreman_smartproxy(facts[:fqdn]).with({ 
    'ensure'          => 'present',
    'base_url'        => "https://#{facts[:fqdn]}",
    'effective_user'  => 'admin',
    'url'             => "https://#{facts[:fqdn]}:8443",
    'consumer_key'    => /\w+/,
    'consumer_secret' => /\w+/,
  })
end
```

You could even consider testing the specific registration in foreman_proxy__register__spec.rb, but the fact you're adding tests is already great :).