How do I create node groups in puppet

I am in the process of setting up Puppet in our QA environment. I have created a few manifests and setup classes which are running fine. I am aware of Node definitions and have successfully created manifests to apply on a few nodes using node definition. But I am yet to figure out how to put a group of nodes into a group so that I can use the groupname instead of having to specify each nodes in the node definition. This URL to the puppetlabs document seem to talk only about group creation in Puppet Enterprise version. How do I create groups in community version?

This is my current nodes.pp file.

[root@puppet modules]# cat /etc/puppet/manifests/nodes.pp
node "saturn.qa1.example.com", "mercury.qa1.example.com" {
      include qa1check
}