root@junglist /tmp# ./test.pp --debug
info: Loading fact configured_ntp_servers
info: Loading fact netmask
info: Loading fact acpi_available
info: Loading fact interfaces
debug: Puppet::Type::User::ProviderNetinfo: Not suitable: missing nireport
debug: Puppet::Type::User::ProviderPw: Not suitable: missing pw
debug: Puppet::Type::User::ProviderDirectoryservice: Not suitable: missing /usr/bin/dscl
debug: Creating default schedules
debug: //Node[junglist]/poo/User[test1]: Changing ensure
debug: //Node[junglist]/poo/User[test1]: 1 change(s)
debug: User[test1](provider=useradd): Executing '/usr/sbin/useradd -u 20014 -g 100 -G admin -s /bin/bash -m test1'
notice: //Node[junglist]/poo/User[test1]/ensure: created
debug: //Node[junglist]/poo/User[test2]: Changing ensure
debug: //Node[junglist]/poo/User[test2]: 1 change(s)
debug: User[test2](provider=useradd): Executing '/usr/sbin/useradd -u 20014 -g 100 -G admin -s /bin/bash -m test2'
err: //Node[junglist]/poo/User[test2]/ensure: change from absent to present failed: Could not create user test2: Execution of '/usr/sbin/useradd -u 20014 -g 100 -G admin -s /bin/bash -m test2' returned 1024: useradd: UID 20014 is not unique

debug: //Node[junglist]/poo/User[test3]: Changing ensure
debug: //Node[junglist]/poo/User[test3]: 1 change(s)
debug: User[test3](provider=useradd): Executing '/usr/sbin/useradd -u 20014 -g 100 -G admin -s /bin/bash -m test3'
err: //Node[junglist]/poo/User[test3]/ensure: change from absent to present failed: Could not create user test3: Execution of '/usr/sbin/useradd -u 20014 -g 100 -G admin -s /bin/bash -m test3' returned 1024: useradd: UID 20014 is not unique

debug: Finishing transaction -610387798 with 3 changes
root@junglist /tmp# cat test.pp
#!/usr/bin/env puppet

node junglist {
   include poo
   User <| groups == admin |>
}


class poo {
   @user {
      [ "test1", "test2", "test3"]:
         ensure => "present",
         uid  => "20014",
         gid  => users,
         groups => admin,
         shell   => "/bin/bash",
         membership => "minimum",
         managehome => true;
   }
}