I have some Ansible roles to configure my vps, Raspberry Pi, etc. I like to test them before I broke something on my real, not clustered machines - I use Vagrant for that.
But with it I had one problem - in playbooks I define hosts as groups of severs ex. web for my vps:

Example Ansible playbook
- hosts: web
  gather_facts: True
  sudo: True

But testing machine wasn’t in this group and when I run vagrant I could only see:

Ansible run
$ vagrant provision
==> default: Running provisioner: fix-no-tty (shell)...
    default: Running: inline script
==> default: Running provisioner: ansible...

PLAY [web] ********************************************************************
skipping: no hosts matched

PLAY RECAP ********************************************************************

To get rid of this I have to add default vagrant machine to my default group in Vagrantfile:

config.vm.provision "ansible" do |ansible|
  ansible.groups = {
    "web" => ["default"]

  ansible.sudo = true
  ansible.limit = "all"
  ansible.playbook = "web.yml"

And that solved my problem 😄