check_resource.rb

require 'puppet'
require 'puppet/type/user'

resource = Puppet::Type::User.new(:name => 'rpinson', :uid => '1502')
# resource = Puppet::Type::Exec.new(:name => '/bin/test', :unless => '/bin/true')
# resource = Puppet::Type::Service.new(:name => 'ssh', :ensure => 'running', :enable => 'false')

# Ensurable
if resource.provider.respond_to?(:exists?) and ! resource.provider.exists?
  return false
end

return resource.insync?(resource.retrieve)  # Catch exceptions